41st Annual Meeting of the Assocation for Chemoreception Sciences

Printable Program & Abstracts

April 14-17, 2019
Bonita Springs, FL

Saturday, April 13, 2019

1:15 - 3:50 PMCalusa ABC
Comparative Approaches to Chemosensory Function

Chair(s): Thomas Bozza

Introduction: Chemosensation In Model And Non Model Organisms
Thomas Bozza
Northwestern University

The Role Of Olfactory Receptors In Odor Perception
Casey Trimmer

Mapping Receptor Expression In The Human Olfactory System
Jay Gottfried
University of Pennsylvania

Specific Receptors, Circuits, And Outputs For Vomeronasal Ligands
Takuya Osakada
University of Tokyo

Snowballs Or Snowflakes: Transcriptional Heterogeneity In Olfactory Sensory Neurons
Tatsuya Tsukahara
Harvard University

Single Cell Transcriptomics For Understanding Connectivity In The Taste Periphery
Nirupa Chaudhari
University of Miami

Rewiring Taste With Semaphorin Signals
Lindsey MacPherson
UT San Antonio

3:50 - 4:05 PMCalusa Foyer
Coffee Break

4:05 - 6:10 PMCalusa ABC
Comparative Approaches to Chemosensory Function

Mosquito Egg-Laying Stimuli
Marcus Stensmyr
Lund University

Odorant Receptors Regulate Odorant Receptor Expression In Anopheles Mosquito Olfactory Neurons
Christopher Potter
Johns Hopkins University

Activation Of Planarian Trpa1 By Reactive Oxygen Species Reveals A Common Mechanism For Chemical And Thermal Nociception
Marco Gallio
Northwestern University

Gene-Editing And Transgenic Tools For Investigating Chemosensory Function In The Clonal Raider Ant
Tom Hart
Rockefeller University

Evolution Of Sensory Perception
Claude Desplan
New York University

Sunday, April 14, 2019

8:15 - 10:00 AMCalusa ABC
Comparative Approaches to Chemosensory Function

Chair(s): Paul Feinstein

Introduction: Mechanisms Of Odorant Receptor Gene Expression

Employing High Probability Gene Choice Enhancer Transgenes To Understand Singular Odorant Receptor Expression
Raena Mina1,2
1Hunter College, 2CUNY GC

Cooperative Cis-Acting Enhancers Govern The Expression Of Trace Amine-Associated Receptors
Ami Shah
Northwestern University

Molecular Mechanisms Of Class Choice In Olfactory Sensory Neurons
Junji Hirota
Tokyo Institute of Technology

Chemoreceptor Gene Cluster-Dependent Stabilization Of Fpr Gene Transcription
Ivan Rodriguez
University of Geneva

Multi-Chromosomal Compartments As Regulators Of Olfactory Receptor Transcription
Stavros Lomvardas
Columbia University

10:00 - 10:15 AMCalusa Foyer
Coffee Break

10:15 - 12:20 PMCalusa ABC
Comparative Approaches to Chemosensory Function

Chair(s): Tim Holy

Introduction: Emerging Methods In Chemosensory Research

Characterizing The Olfaction Of Social Behavior With Multiplexed Imaging
Bogdan Bintu
Harvard University

Transsynaptic Mapping And Manipulation Of Gustatory Circuits In Flies By Trans-Tango
Gilad Barnea
Brown University

Probing The Olfactory Code With Light
Dmitry Rinberg
New York University

Functional, Three-Dimensional Spatial Transcriptomics In The Mammalian Olfactory Bulb
Alex Fleischmann
Brown University

A Molecular Logic Of Sensory Coding Revealed By Optical Tagging Of Physiologically-Defined Neuronal Types
Tim Holy
Washington University

12:00 - 4:00 PMGreat Egret
AChemS Executive Board Meeting (Invite Only)

5:00 - 6:00 PMCalusa ABCD
Welcome/Awards Ceremony

6:00 - 7:00 PMCalusa ABCD
Givaudan Lecture


The Chemical Senses And Eating: Mouth As Integrator, The Temporal Aesthetics Of The Meal, And Reversing Innate Aversions

Paul Rozin
Department of Psychology, University of Pennsylvania, Philadelphia, PA, United States

Aside from breathing, eating is our most pressing and important function, and has a special relation to the mouth and the chemical senses.  Typically, in a meal we have a sequence of chemosensory experiences, and the way this sequence is experienced and integrated influences the aesthetic pleasure of the meal.  Main dishes in most cuisines present a characteristic set of flavors (flavor principles).  One of the most common such flavorings is chili pepper, which is surprising because it is innately aversive.  The process through which an innately aversive oral experience becomes positive will be discussed, and related to a much more general and uniquely human phenomenon: benign masochism.

7:00 - 9:00 PMPool Deck & Cypress Courtyard
Welcome Banquet

Join us for the traditional AChemS Welcome Banquet, the first opportunity to reconnect with colleagues and kick the meeting off right! Cash bar is available. An RSVP was required at time of registration and your ticket is available in your name badge; additional tickets can be purchased at the Registration Desk.

9:00 - 11:00 PMMangroves Patio
Graduate Student Happy Hour

A relaxed, casual gathering and opportunity to mingle with other graduate students over a cocktail! The patio of Mangroves will be the exclusive gathering spot for this event. Cash bar.

Monday, April 15, 2019

7:30 - 9:00 AMEstero Foyer

8:00 - 10:00 AMEstero Ballroom
Poster Session I

Creeping On Ants: Developing The Pispy, An Affordable And Flexible Video Recording Platform For Monitoring Animal Behavior
Marcy J Kittredge1, Andrew Hawk2, Owen Meng2, Matt Lamparter2, Thomas Thul3, Gregory M Pask1
1Bucknell University Department of Biology, Lewisburg, PA, United States, 2Bucknell University Department of Electrical and Computer Engineering, Lewisburg, PA, United States, 3Bucknell University Department of Biomedical Engineering, Lewisburg, PA, United States

Many behaviors related to chemosensation can occur almost immediately following a stimulus, but others may result from prolonged exposure and may be difficult to capture through direct observation. In our own research model, the Indian jumping ant Harpegnathos saltator, the array of chemically-mediated social behaviors can extend across hours to days. Automated systems to record animal behaviors can be a valuable tool in the field of ethology, but the cost can be prohibitive for many researchers, particularly those from low income countries. We have developed an affordable, customizable, and easy-to-use video monitoring device, the PiSpy. The PiSpy platform is based on a Raspberry Pi computer and is designed to be able to record and monitor behaviors at any time in both light and dark conditions. To run this fully automated recording system, we developed a graphical user interface (GUI) to control each aspect of recording, such as frequency, duration, lighting control, etc. As a versatile recording device, several components of the PiSpy can be customized to fit the study species and research question. Additionally, the PiSpy is affordable at ~$120, with many of the parts being homemade or easily attainable. We have piloted the PiSpy in ant behavioral tracking, and aim to extend its utility to several other animal models. We hope that our open-source PiSpy video recording platform, with its accessibility, flexibility and affordability, will contribute to many research advances within the biological sciences and beyond.

Resting State Olfactory Network Functional Connectivity With The Right Hippocampus In Alzheimer&Rsquo;S Disease
Jiaming Lu1,2, Nicole Testa1, Rebecca Jordan1, Qing Yang1, Prasanna Karunanayaka1
1Radiology, Center for NMR Research, Penn State University College of Medicine, Hershey, PA, United States, 2Medical School of Nanjing University, Nanjing, *, China

The olfactory and memory-related brain regions are selectively vulnerable in Alzheimer’s disease (AD). Longitudinal studies of AD patients have indicated that olfactory deficits are related to the severity of dementia. Thus, the connectivity between the olfactory network (ON) and the hippocampus may play an important role in AD pathophysiology. Currently, very few studies have been conducted to investigate AD-related olfactory deficits from a network perspective. This is important because AD is a neural network-based degeneration where neuropathology spreads and disrupts across networks. Here, we explored the resting state functional connectivity (FC) of the ON in subjects who were aged-matched cognitively normal (CN), early mild cognitive impairment (EMCI), late MCI (LMCI) and AD to systematically investigate its potential as an indicator of AD neurodegeneration. We analyzed resting state data from one hundred forty seven (147) subjects from the Alzheimer's disease neuroimaging initiative (ADNI: at http://www.adni-info.org/). Results showed differences in ON FC among the CN, EMCI, LMCI and AD groups in the right hippocampus. Further, the ON FC was significantly different between EMCI and LMCI groups. No significant differences in hippocampal volume were observed between the EMCI and LMCI. ON hippocampal FC values are significantly correlated with cognitive test scores likely reflecting the progression of AD. The decrease in FC between ON and hippocampus offers a unique opportunity to investigate direct and specific effects of neurodegeneration during AD progression. Future studies aimed at validating the current findings and longitudinal investigation of the functional integrity of the ON FC will provide further insights into the relationship between olfactory and cognitive deficits in AD.

Drawing The Borders Of Olfactory Space
Emily J. Mayhew, Charles J. Arayata, Jonathan Magill, Lindsey L. Snyder, Chung Wen Yu, Joel D. Mainland
Monell Chemical Senses Center, Philadelphia, PA, United States

In order for researchers to rigorously sample it, the boundaries of olfactory space must be defined. In studies of vision and audition, stimuli can be chosen to span the visible or audible spectra; in olfaction, the axes and boundaries that define olfactory space are unknown. Without these defined boundaries, it is also difficult to quantify the number of possible odorous molecules. An estimate of 10,000 odorants is often cited, but the quality and source of this figure is unclear.  A model proposed by Boelens (1983) draws a border between odorous and odorless molecules using boiling point (bp) and hydrophobicity (Kow), but the accuracy of the model and the data used to construct the model are undefined. Here we selected 128 diverse compounds that span a wide range of chemical space. Human subjects evaluated these compounds in 3-alternative forced choice discrimination tests. We reserved 30 molecules to form a validation set, then employed several machine learning algorithms to iteratively train and test models on the remaining 98 compounds. Random Forest (RF) models achieved the highest accuracy (86 ± 2.2%) and showed improvement over logistic regression models constructed using only bp and Kow (77 ± 1.1%). We identified several physicochemical properties, in addition to bp and Kow, that help distinguish odorous from odorless molecules, including electrophilicity and structure linearity. Applying our current model to the GDB17, a database of all possible molecules with 17 or fewer heavy atoms (C, N, O, S, or halogens), we estimate that over 27 billion possible compounds are odorous. In drawing the borders of olfactory space more clearly, we provide necessary guidance for olfactory researchers to design experiments that representatively samples olfactory space.

A Measure Of Smell Enables Creation Of Olfactory Metamers
Aharon Ravia1, 3, Kobi Snitz1, Danielle Honigstein1, Maya Finkel1, Ofer Perl1, Christophe Laudamiel2, David Harel3, Noam Sobel1
1Department of Neurobiology, Weizmann Institute of Science, Rehovot, *, Israel, 2DreamAir LLC, New York, NY, United States, 3Department of Computer Science and Applied Mathematics, Rehovot, *, Israel

Over 100 years ago, none other than Alexander Graham Bell challenged: "we have very many different kinds of smells, all the way from the odor of violets and roses up to asafoetida. But until you can measure their likenesses and differences you can have no science of odor”. Such a measure of smell, can exist, and several such models have recently been put forth. These models rely on finding rules that link odorant structure to aspects of odor perception. Here we collected 38,744 perceptual odor estimates from 166 participants, and building on one such model, finalize a physicochemical measure of smell. The measure, expressed in radians, precisely predicts real-world odorant perceptual similarity from structure alone. Using this measure, we met Bell's challenge by accurately predicting the perceptual similarity of rose, violet and asafoetida, from their physicochemical structure. Next, we identified the smallest difference, where humans can still tell odorants apart. This is the just-noticeable-difference (JND) in olfaction, which we place at 0.0125 radians. The JND allowed us to generate olfactory metameres. We further applied the JND to estimate human olfactory capacity. Using our metric and JND we estimate the number of different olfactory stimuli humans can discriminate. According to initial results the number of distinct odors human can discriminate exceeds one trillion, making discrimination capabilities unbounded. We claim that this overcomes previously introduced methodological concerns for capacity estimation. The characterization of a physical measure and related JNDs in vision and audition was a critical step towards understanding their underlying neurobiology, and towards their ultimate digitization. We suggest that the olfactory measure and JND may do the same for olfaction.

Ants As Emerging Models To Study Chemosensory Neuroplasticity
Hua Yan1,2, Shadi Jafari3, Danny Reinberg4, Claude Desplan3
1University of Florida Department of Biology, University of Florida Center for Smell and Taste (UFCST), Gainesville, FL, United States, 2University of Florida Center for Smell and Taste (UFCST), Gainesville, FL, United States, 3Department of Biology, New York University, New York, NY, United States, 4Howard Hughes Medical Institute (HHMI), Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, United States

Animal behavior is best understood as an emergent phenomenon based on the dynamic interpretation of sensory stimuli by the brain. Eusocial insect, including ants, display advanced form of sociality with striking phenotypic differences, between nearly genetically identical queen and worker castes. To precisely distinguish the social cues, ants evolved more complex chemosensory system, where odorant receptor genes (ORs) were dramatically expanded during social evolution. We have generated germline mutation in orco (OR coreceptor) in the ant Harpegnathos saltator and found that OR functionality is essential for pheromone-induced social cooperation, reproductive physiology and proper neurodevelopment (Cell 170(4): 736-747). Our further analyses on orco mutant ants reveal differential dependence of orco in the development and survival of odorant receptor neurons (ORNs). Interestingly, although male and female ants display striking differences in the OR expression pattern, most of neurons die in the absence of orco. However, the survival of a small group of ORNs are independent of orco and probably neuronal activity in both male and female ants. We have identified orco-dependent vs. orco-independent ORNs and will further address how they differentially regulate neural development.

Social Experience Reprograms Olfactory Receptor Neuron Function Through Chromatin Mediated Changes In Gene Expression
Bryson Deanhardt, Songhui Zhao, Pelin Volkan
Duke University, Durham, NC, United States

Epigenetic regulation of transcription in response to environmental cues can lead to enduring behavioral changes. However, mechanisms driving these changes at the molecular, circuit, and behavior level remains unclear, as models allowing for such multiscale investigation are lacking. Using Drosophila courtship behavior as a model, we found that social experience via pheromonal cues induce chromatin-based changes in the expression of the gene fruitless (fru), a master regulator of courtship behaviors. Male-specific splice isoform of Fru, FruM, is necessary and sufficient for driving male courtship behaviors and is expressed in approximately 2,000 interconnected neurons that constitute the courtship circuit. In the olfactory system fruM is expressed in Or47b and Or67d olfactory receptor neurons (ORNs), which detect pheromones. Among these, Or47b ORNs detect palmitoleic acid (PA), and increase the competitive courtship advantage of males. We recently showed that Or47b signaling and histone acetyl transferase p300 activity are required for fruM expression in the olfactory system and the brain. In addition, social isolation decreased fruM expression in Or47b ORNs, which was rescued by exposure to PA or regrouping. Chromatin immunoprecipitations from group housed, socially isolated, and Or47b mutants showed concomitant changes in chromatin. For example, RNA polymerase and p300 enrichment around fru promoter, as well as open chromatin marks associated with p300 activity in group housed males, were significantly decreased in socially isolated males and Or47 mutants. Chromatin differences in socially isolated males were rescued to group housed levels upon regrouping. Our results suggest that chromatin-based changes in fruM transcription with social experience can modulate ORN function and courtship behavior.

Investigating Glial And Axonal Adaptations To Sensory Deprivation In The Olfactory System
Nicholas M. George, Wendy B. Macklin, Diego Restrepo
University of Colorado Anschutz Medical Campus, Aurora, CO, United States

The olfactory system is unique among sensory systems in that it remains plastic throughout life and is one of the few brain regions to actively integrate new neurons into adulthood. The olfactory system encompasses several dedicated brain regions, such as the olfactory bulb (OB) and piriform cortex, which are connected by large, myelinated tracts. Precise control of conduction velocity and the synchronized firing of mitral cells (MC), the myelinated projection neurons of the OB, are vital to olfactory sensory perception in piriform cortex. We are investigating the impact of neural activity on myelin and axonal function in the olfactory system, focusing on MC axon myelination. MC AISs were labeled with antibodies against the cytoskeletal scaffolding protein AnkyrinG. Confocal z-stacks (XY pixel size = 0.310um, step size 0.25um) were taken from horizontal sections of the mouse OB in the MC layer from both occluded and open bulbs. We observed myelin sheaths abutting directly against the axon initial segments (AIS) in the MC project layer. We use unilateral naris occlusion in adult mice to investigate myelin and axonal plasticity in response to sensory deprivation. Following 30 days of naris occlusion, we observed a significant shortening of MC axon initial segments (AIS) in the occluded OB. To investigate the electrophysiological consequences of these adaptations following naris occlusion, we are performing extracellular recordings of conduction velocity and axon refractoriness, as well as patch clamp recording and cell filling to link structural changes of the axon and myelin sheath to differences in signal processing in the olfactory system. Our data support an additional form of plasticity for the olfactory system in which axons and myelin adapt to changing olfactory inputs.

Defining The EMbryo-To-ADult TRansition (Eat) In Mouse Taste Bud Development And Regeneration.
Erin J. Golden, Timothy J. Fellin, Linda A. Barlow
Dept of Cell & Developmental Biology and the Rocky Mountain Taste and Smell Center. University of Colorado School of Medicine., Aurora, CO, United States

Taste buds are collections of heterogeneous taste receptor cells (TRCs) that detect sweet, sour, salt, bitter, and umami. TRCs are continually replaced by proliferative keratin (K) 14 and 5+ progenitor cells situated adjacent to buds. In mouse embryos, taste bud precursors are first evident as small clusters of columnar epithelial cells or placodes on the tongue surface. Each placode comprises 10-20 cells that express both K8 and a secreted protein Sonic Hedgehog (SHH). SHH+ placode cells differentiate into TRCs in the first postnatal (P) week, but do not give rise to K14+ progenitors that support adult TRC renewal (Thirumangalathu et al., 2009 Development). This raised the questions of how and when TRC turnover commences. Using 3D image analysis, we find taste placode and taste bud cell number are static during embryonic development and within 1-2 days of birth, respectively; while EdU incorporation studies and K14 genetic lineage tracing reveal that the progenitor contribution to taste buds begins by P2, steadily increasing through P14 as taste bud cell number rapidly expands. During embryonic development, SHH represses taste fate, limiting the number and size of taste placodes (Hall et al. 2003 Dev Biol), while in adults SHH overexpression induces ectopic taste bud formation (Castillo et al. 2014 Development). Thus, we hypothesized the switch in SHH function coincides with the onset of TRC renewal. Using K14CreER to drive SHH overexpression at specific postnatal time points, we find that SHH drives ectopic taste cell formation starting at birth and this capacity ramps up over the first two postnatal weeks. Using RNAseq of P0 lingual epithelia, we have identified and are now exploring specific candidate transcription factors whose function may mediate this shift in the epithelial response to SHH.

Astrocytic Response To Neonatal Chorda Tympani Transection Is Larger Compared To Adult Transection
Andrew J. Riquier, Suzanne I. Sollars
University of Nebraska at Omaha, Omaha, NE, United States

Transection of the chorda tympani nerve (CTX) in adult (> 40 days of age; P40) rats, results in transient loss of fungiform taste buds, temporary morphological changes in papillae, and a preserved CT terminal field in the rostral nucleus of the solitary tract (rNTS). In contrast, CTX performed at ≤ P10 leads to permanent loss of both fungiform taste buds and papillae, and near total degeneration of the CT terminal field (Martin & Sollars, in press). Our laboratory’s previous research demonstrated that P10 rats show an attenuated microglia response to neonatal CTX, relative to adult CTX (Riquier & Sollars, 2017). In the current study, we assessed both astrocytes and microglia in the rat rNTS 4- and 14-days after CTX at P10 or P50. Iba1+ microglia increased in the rNTS at all time points examined, with a larger response after P50 CTX as compared to P10 CTX (ps <.05). Consistent with previous work in the mouse (Bartel, 2012), P50 CTX induced an increase in GFAP+ astrocytes in the adult rNTS.  Notably, and in contrast to the microglia responses, we observed that the astrocyte response to P10 CTX was substantially larger (p <.05) than that of adults and limited to 4-days post (p <.05), with a return to baseline quantities by 14-days post (p > .1). Our results suggest developmental differences in the central glia response to CTX that correspond to differences in recovery outcomes.

Ephrin-A'S Guide Embryonic Gustatory And Somatosensory Afferents In Fungiform Papilla Epithelium
M. William Rochlin1, Albert J. George1, Alexandria M. Calmes1, Marissa K.L. Pilon1, Kajol H. Doshi2, Jason S. Hwang1, Randall W. Treffy3
1Loyola U Chicago, Chicago, IL, United States, 2Albany Medical College, Albany, NY, United States, 3University of Illinois Chicago, Chicago, IL, United States

Diffusible factors (neurotrophins and semaphorins) have key roles in guiding gustatory (geniculate) and somatosensory (trigeminal) afferents to their neighboring targets in gustatory papilla epithelium but non-diffusible cues are also likely to be involved. Ephs and ephrins are cell surface proteins that act as ligands and receptors for one another, initiating signaling cascades that can cause repulsion, arborization, or growth promotion of axons. There are two classes of Ephs and ephrins: ephrin-A’s are lipid-linked proteins that interact predominantly with EphAs, whereas ephrin-Bs are transmembrane proteins that interact predominantly with EphBs. During axon targeting in rats and mice, antibodies against ephrin-A1, -A3, -A4, and -A5 label the lingual epithelium broadly, but the labeling is less intense in gustatory papilla epithelium and the core tissue traveled by afferents.  In situ hybridization results support these findings in mice.  Ephrin-A2 mRNA is also present in tongue sections, but staining is less dense overall than staining for the other 4 ephrin-A’s, and less elevated in the epithelium compared to the mesenchyme. Anti-EphA5 and -EphA7 label afferents within nascent fungiform papillae. Geniculate and trigeminal neurites are repelled dose dependently by stripes of ephrin-A-Fc fusion proteins in vitro. Intriguingly, ephrin-A3 repels E18 rat-derived geniculate neurites with significantly greater potency than trigeminal neurites. Despite the expression of all 5 ephrin-A’s in lingual epithelium, preliminary results suggest that knocking out 3 (ephrin-A1,A3,A4) is sufficient to widen axon terminal arbors in fungiform papillae. These data are consistent with a role for ephrin-A/EphA signaling in restricting exploration of sensory afferents within the target epithelium.

Social Experience And Hormone Signaling Collaborate To Modulate FruM Expression In The Adult Olfactory System
Songhui Zhao, Bryson Deanhardt, Pelin Volkan
Duke University, Durham, NC, United States

   Courtship behaviors in Drosophila are regulated by a single gene fruitless (fru), where sex-specific alternative splicing of fru generates the FruM protein only in males. FruM is necessary and sufficient to drive male-specific courtship behaviors. Olfaction is a key regulator of courtship behaviors, as flies detect odors and volatile pheromones via olfactory receptor neurons (ORNs) to modulate courtship. In the olfactory system, three ORN classes are associated with courtship behaviors and express fruM: Or67d, Or47b, and Ir84a. Previously, our lab found that expression of fruM in Or47b and Ir84a ORNs requires Or47b and Ir84a signaling, whereas in Or67d ORNs, fruM expression is independent of Or67d function. This difference in fruM regulation might reflect functional differences of Or47b and Ir84a ORNs from Or67d ORNs. Indeed, Or47b detects pheromones, particularly palmitoleic acid (PA), and is required for the increase in copulation advantage in older males. This change in courtship behavior is due to changes in Or47b ORN neurophysiology partly driven by juvenile hormone receptor methoprene-tolerant (met). We predicted that Or47b and Met can modify male courtship behaviors through reprogramming fruM expression in OR47b ORNs using social olfactory experience and hormone signaling. Indeed, fruM expression in OR47b ORNs is significantly higher in group housing flies compared to socially isolated flies. Also, Met function is required for fruM expression in adult Or47b ORNs.Our data suggest that pheromone signaling of social environment through calcium activity and chromatin modulation, together with hormone signaling, reprogram fruM expression in Or47b ORNs to drive behavioral adaptations.

Evidence For Primacy Coding In Human Olfaction
Terry Acree1, Chloé Albietz2, Dmitry Rinberg3
1Cornell University, Ithaca, NY, United States, 2Givaudan, Lausanne, *, Switzerland, 3New York University, New York, NY, United States

Object recognition is one of the basic properties of all sensory systems. Humans and other animals can identify smells independently of their concentrations. Recently, we proposed a novel model for concentration invariant odor recognition, based on the importance of earlier activated receptors. A higher concentration of an odorant activates a larger population of the receptors. Thus, only a small ensemble of receptors, which is activated by both low and high concentrations can be responsible for odor identification. According to our model, called Primacy coding, this ensemble is activated first and defines an odor identity. Recent animal experiments provide an evidence toward this model. Mice can discriminate odors based only on a short temporal window (~100 ms) at the beginning of a sniff cycle (Wilson 2017) and cortical representation is formed very quickly after an onset of odor exposure (Bolding 2017).   Can this model be applied to human odor perception? We designed an experimental approach based on a binary odor mixture discrimination. Subjects were asked to identify odors A or B delivered simultaneously at different concentration ratios. We estimated a concentration ratio correspondent to equal probability of detecting odor A or B: Equal Odd Ratio (EOR). Our apparatus allowed us to controllably change the relative timing of individual odorants delivery with less than 50 ms temporal precision, while keeping all other parameters of odor delivery the same (Rochelle 2017). We found that the delivery of odorants at EOR with a temporal shift, systematically increased probability of detecting an earlier odorant. And this effect is observable at temporal shifts smaller than 50 ms. This is strong evidence that early events during odor exposure are responsible for odor recognition in humans.

Psychometric Functions In Odor Detection
E. Leslie Cameron1, Richard L. Doty2
1Department of Psychological Science, Carthage College, Kenosha, WI, United States, 2Smell & Taste Center, University of Pennsylvania, Philadelphia, PA, United States

Psychometric functions in olfaction are relatively understudied.  Both dogs and humans produce unusually-shaped olfactory psychometrics functions – significant ‘notches’ exist in performance as a function of concentration. This is true for performance on a discrimination task, but not for confidence judgements of those discriminations (Cameron & Doty, AChemS 2018). In this study we ask: Do psychometric functions exhibit a ‘notch’ in a detection task?  College students performed a yes/no detection task using “Snap & Sniff®” wands. On each trial, two wands were presented in rapid succession. On target present trials, one wand contained amyl acetate (the target) at one of 10 predetermined concentrations and the other contained mineral oil, whereas on target absent trials, neither wand contained amyl acetate. The participant’s task was to indicate whether the unnamed target odor was present or not and to rate their confidence (on a scale of 1-9).  Verbal feedback was provided on each trial. Thirty-six undergraduates (20 females) completed one 30-minute session of 80 trials. As we observed in a discrimination task, performance (hit rate for odor detection) increased as a function of concentration, following a sigmoidal pattern for both males and females. Moreover, ‘notches’ in the psychometric function were observed at low concentration. Confidence ratings increased with concentration in the detection task, as it did in the discrimination task.  However, there was a pronounced ‘notch’ in the function at low concentration in the detection task, which may be a result of the trial-by-trial feedback that was necessary in this task.  ‘Notches’ in psychometric functions for both detection and discrimination tasks may reflect dual-mechanisms at the receptor level. 

Sensitivity To Subtle Changes In Wine Odor
Michelle Heatherly, Robert Pellegrino, Curtis Luckett
University of Tennessee, Knoxville, TN, United States

Previous findings on odor mixture discrimination have suggested that subtracting a component from an odor mixture is less likely to be detected than when a component is added. Additionally, familiarity with the odorants could also play a role in the difficulty of odor discrimination tasks. The goal of this study was to determine whether odor mixtures were easier to discriminate when an odor compound was added, or when an odor was removed. We further wished to evaluate whether expertise had any bearing on discrimination abilities. To do this, wine experts and novices were used to assess whether discrimination was altered with the addition/subtraction tasks. After producing a model wine odor in which odor compounds could easily be manipulated, a homologous series of esters, varying in chain length, were chosen as odor modifiers (added at threshold level). A-not-A tests were then used to gauge the discriminatory ability of experts and novices. Participants as a whole were not able to discriminate between either the addition or subtraction samples at rates above chance (p = 0.7741). Furthermore, expertise did not seem to play a role in discriminatory abilities, with experts and novices discriminating similarly (p = 0.3705). Overall, the stimuli were difficult to discriminate between and no evidence was found that subtracting an odor from a mixture was a more difficult task.

The Sweet Taste Of Acarbose And Maltotriose: Relative Detection And Underlying Mechanism
Alexa J Pullcin, Michael H Penner, Juyun Lim
Oregon State University, Corvallis, OR, United States

Despite having similar molecular structures, the relative sweetness of different saccharides can vary considerably. Current understanding of saccharide structure/sweetness interrelationships is limited. An approach to improving this understanding is to generate insightful data on the correlations between the structural features of saccharides, and/or saccharide analogs, and their relative sweetness. Maltotriose is a short-chain glucose oligomer, which we recently reported to have sweet taste. Acarbose is a structural analog of a glucose oligomer. During other studies, we recognized that acarbose can also elicit sweet taste above a certain concentration. In the first experiment, we formally investigated the underlying taste detection mechanism of acarbose along with maltotriose; when the sweet taste receptor was inhibited, human subjects were no longer able to discriminate acarbose or maltotriose from blanks. In the second experiment, we measured the relative sweetness detection of acarbose, maltotriose, and other sweet-tasting mono- and disaccharides (glucose, fructose, maltose, and sucrose) that have different structural features. We found that maltotriose has similar discriminability to glucose and maltose at the concentrations tested (18, 32, and 56 mM), while the discriminability of acarbose closely matches that of fructose. Study findings are discussed in terms of how specific molecular feature (e.g., degree of polymerization and monomer composition) may contribute to the relative sweetness of saccharides.

Human Olfactory Discrimination Of Genetic Variation In Cannabis Strains
Anna Schwabe1, Mitchell McGlaughlin1, Avery N. Gilbert2
1University of Northern Colorado, Greeley, CO, United States, 2Headspace Sensory LLC, Fort Collins, CO, United States

Varietals of dried Cannabis flower are sold under many names. Strain-specific aroma profiles are distinctive (Gilbert & DiVerdi, 2018a), and robust with respect to sensory methodology (Gilbert & DiVerdi, in press). Cannabis samples from different sources, sold under the same strain name, show genetic inconsistencies (Schwabe & McGlaughlin, in press). Genetic variation may lead to differences in consumer-relevant phenotypic traits such as terpene content. By combining molecular genotyping and olfactory phenotyping techniques, we sought to determine whether genetically inconsistent samples within a commercial strain display inconsistent aroma profiles. We genotyped 42 samples from 5 strains. For each strain, we elucidated a consensus genotype and genetic outliers (if any) based on 10 variable microsatellite regions. Four strains (15 samples) were selected for olfactory testing: Blue Dream (5), OG Kush (4), Mob Boss (3), and Durban Poison (3). Aroma profiles were produced by 55 untrained sniff panelists (33 men, 22 women) using check-all-that-apply ballots with 40 previously validated odor descriptors. The aroma profile of the Mob Boss outlier was at odds with the consensus samples as well as the strain’s previously observed aroma profile. All OG Kush samples displayed the strain-typical profile, but the outlier also scored high on an atypical cheese note. The Blue Dream outlier was far more pungent, chemical, and skunk-like than the mean of the consensus samples. All Durban Poison samples (no outlier available) clustered together. It appears that within-strain differences identified by microsatellite genotyping are associated with differences in aroma profile.

Profiling The Dynamic Perception Interaction Of Simplified Lemonade Using Temporal Dominance Of Sensations (Tds) And Temporal Check-All-That-Apply (Tcata)
Anna Z. Wu, Rachel W. Lee, Bénédicte Le Calvé , Isabelle Cayeux
Firmenich Inc., Plainsboro, NJ, United States

Though a number of studies have examined the impact of flavorants and their interactions on the sensory perception of various beverages, less is known about the time course of sensory interaction during beverage consumption. Here, we studied the impact of citric acid level and type of sweetener on dynamic perception of simplified lemonade using TDS and TCATA. We found that citric acid level did not impact perception of lemon flavor. Instead, the sweetener type had an impact on the rate and duration with which lemon flavor was perceived as dominant in TDS, but not its overall citation duration and rates in TCATA. In terms of licorice taste, certain high-intensity sweetener solutions with higher levels of citric acid had relatively lower dominance/citation rates and duration than the high-intensity sweetener samples with lower levels of citric acid. Sweetness was perceived to be more dominant and more frequently cited for sucrose than the high-intensity sweetener solutions, especially at the early tasting stage.  Finally, results showed that both TDS and TCATA provided useful and complementary information for the study of sensory interactions.

Characterizing Cisplatin-Induced Dysgeusia In A Mouse Model
Carlos L. Green, Sara C.M. Leijon, Amanda F. Neves, Stephen D. Roper
Miller School of Medicine, Univ of Miami, Miami, FL, United States

Platinum-based chemotherapeutic agents such as cisplatin are commonly used as part of the primary treatment regimen for many cancers including gastric, testicular, lung, and head and neck cancers.  However, these agents cause the under-appreciated side effect of dysgeusia that often results in reduced appetite, reduced nutritional intake, and a poor quality of life. Here, we aim to characterize the acute effects of cisplatin on taste in order to guide the development of effective therapies to prevent dysgeusia. We employed in vivo Ca2+ imaging of mice geniculate ganglion neurons (Wu et al 2015) to investigate how cisplatin treatment alters responses to prototypical taste stimuli for sweet (sucrose), salty (NaCl), sour (citric acid) and bitter (cyclohexamide/quinine) tastes via oral lavage. Additionally, we immunostained fungiform papilla taste buds to determine the effects of cisplatin treatment at the level of taste receptor cells. We found that there was a significant increase in spontaneous activity in neurons in the geniculate ganglion in cisplatin-treated mice versus their untreated counterparts. Immunohistochemical analysis revealed an abnormal morphology in nearly half of the taste buds, suggesting that neurotoxic effects of cisplatin in the peripheral gustatory sensory organs may be partially responsible for altered responses at geniculate ganglion. Here, we present a method for studying taste change that may be applied to a various therapies and procedures and thus helpful in elucidating mechanisms and therapeutic interventions for chemotherapy-induced dysgeusia.

Dysgeusia, Hypogeusia And Hypergeusia Among Us Adults Aged >40 Years: The National Health And Nutrition Examination Survey (Nhanes), 2011-2014
Howard J. Hoffman1, Linda M. Bartoshuk2, Katalin G. Losonczy1, Shristi Rawal3, John E. Hayes4, Chuan-Ming Li1, Valerie B. Duffy5
1Epidemiology and Statistics Program, National Institute on Deafness and Other Communication Disorders (NIDCD), National Institutes of Health (NIH), Bethesda, MD, United States, 2University of Florida Center for Smell & Taste, Gainsville, FL, United States, 3Department of Clinical and Preventive Nutrition Sciences, Rutgers University, Newark, NJ, United States, 4Department of Food Science and Graduate Programs in Neuroscience and in Nutrition, Pennsylvania State University, University Park, PA, United States, 5Department of Allied Health Sciences, University of Connecticut, Storrs, CT, United States

Risk factors for self-reported dysgeusia and clinically assessed altered taste function were examined using data from NHANES, a continuous cross-sectional, nationally-representative health and dietary survey. Participants (n=7413; aged ≥40 years) answered questions about taste and smell, including problems last year, changes relative to age 25, and dysgeusia (persistent tastes or other sensations in the mouth last year). In 2013–2014, a subsample (n=3114) used the generalized Labeled Magnitude Scale (gLMS) to rate whole mouth and tongue tip intensities of .32 and 1 M NaCl and 1 M quinine. Hypo- and hypergeusia were defined by intensity cut-points of the 10th and 90th percentile for those aged 40–54 years. Potential risk factors included sociodemographic variables and self-report of clinical problems and diseases. Prevalence of dysgeusia was 5.24% (~7.6 million US adults aged ≥40 years); persistent mouth sensations were described as: metallic 30.4%; bad/foul 24.2%; bitter 22.8%; sour 9.9%; burning/tingling 8.1%. Dysgeusia was strongly associated with dental problems last year: 17.8% of those who reported mouth aching was very often vs. 3.1% if never aching (p<0.001). Dysgeusia was also associated with self-rated health of teeth and gums (poor 10.5% vs. excellent 2.4%; p<0.001). Hypogeusia was increased for men and history of 3+ ear infections. Dysgeusia shared risk factors with hypergeusia, e.g., higher in women and those with less education or income. Frequent dry mouth was very strongly associated (6-fold increased risk) with dysgeusia. Reported cancer diagnosis and poor quality of life due to taste/smell problems were also increased for dysgeusia and not associated with hypo- or hypergeusia. In part, these associations replicate earlier identified clinical risks for altered taste perception.  

Bitter Painful Post-Traumatic Trigeminal Neuropathy
Salomé Mascarell1,2, Adeline Braud1,3, Wisam Dieb1, Nathan Moreau1,4, Yves Boucher1,2
1Laboratory of Orofacial Neurobiology, Faculty of Dental Medicine, Paris Diderot University, Paris, *, France, 2Department of Dental Medicine, Pitié-Salpêtrière Hospital, AP-HP, Paris, *, France, 3Department of Dental Medicine, Rothschild Hospital, AP-HP, Paris, *, France, 4Department of Dental Medicine, Bretonneau Hospital, AP-HP, Paris, *, France

Dental treatments causing nerve damage such as endodontic treatments (ET) may elicit painful post-traumatic trigeminal neuropathy (PPTTN). Treatments of PPTTN are often ineffective resulting in impairment of quality of life. Pain is usually described as a burning, pricking or unpleasant mechanical sensation. Gustatory complaints are usually not reported or lack specific investigation. We describe here an unusual case of PPTTN presenting as a bitter sensation. A 52-year-old woman menopaused for 5 years, with no salient medical history was referred to our Pain consultation. In 2013, moderate pain on tooth #16, lead to a first ET, second ET and extraction 1 year and 3 years later respectively. Tooth 16 was replaced with a bridge. Intense and unpleasant bitterness was felt in the vicinity of teeth 13-16 leading to a change in prosthodontic material without any relief. Previously tested treatments including gabapentin, pregabalin, clonazepam, amitriptyline, duloxetine and topical capsaicin were ineffective. The patient reported a permanent, diurnal, bitterness/sourness/almost burning sensation on the hard palate in the vicinity of 13-16, rated as 9 (0-10 scale) and occasional dysesthesias in the lips but no dysgueusia. Probing the painful area elicited a gag reflex. Pain was enhanced by pressure but alleviated by light touch. Local anesthesia stopped the pain and the gag reflex. Electrogustometry performed on the palate and tongue indicated elevated gustatory thresholds on the half of the tongue ipsilateral to the painful symptoms. We hypothesized a PPTTN impairing trigeminal chemo-sensitive (bitter) neurons  and tested botulinum toxin. 37.5 UI were injected in the painful area. No improvement was noted at 14 days. Novel treatment options are currently being tested

Successful Treatment Of Burning Mouth Syndrome With And Without Geographic Tongue And Its Effect On Taste
Nan Su1, Crystal Dewan1, Cindy Liu1, Renee Poon1, Mark Darling3, Miriam Grushka1,2
1Dr. Miriam Grushka, Private Oral Medicine Clinic, Toronto, *, Canada, 2 William Osler Health System, Etobicoke General Hospital, Toronto, *, Canada, 3Schulich School of Medicine and Dentistry, University of Western Ontario, London, *, Canada

Burning mouth syndrome (BMS) is an oral mucosal pain syndrome with burning but no structural changes associated with taste complaints in 68% of patients. Geographic tongue (GT) is a benign disorder with well-demarcated inflammatory lesions and can be associated with taste changes. In our previous study, 27 % of BMS patients had GT. Our current aim is to determine if BMS with GT (BMGT) patients respond similarly to BMS (no GT) and if taste improves following pain reduction. Taste loss patients (TL) served as positive control. Methods  A retrospective study was conducted. Spatial taste testing and subjective pain at first visit and after symptom reduction were collected. BMS and BMGT were treated with clonazepam, gabapentin, and/or pregabalin and TL with zinc and alpha lipoic acid  Results The study included 33 BMS, 6 BMGT, and 5 TL. BMS group had significant reduction in subjective maximum (62.4±22.1, 25.0±8.9, p<0.001) and minimum (18.0±20.4, 5.9±6.7, p=0.001) pain post treatment. Pain reduction in BMGT was not significant (max 53.0±0.00, 19.5±5.2, p=0.063; min7.5±2.9, 8.0±3.5, p=0.458). Salt perception improved significantly in BMS (FP 18.7±17.4, 24.3±15.2, p=0.024; CP 27.14±16.7, 39.9±22.7, p<0.001), BMGT (CP 18.1±15.3, 30.0±17.7, p=0.050) and TL (FP 9.8±11.0, 26.8±14.5, p=0.022). Ethanol response significantly increased only in BMS (FP 35.9±26.1, 46.6±27.0, p=0.025). Sweet improved significantly only in TL (FP10.8±11.7, 26.4±14.6, p=0.012). Conclusion Medication significantly decreased subjective pain in BMS but not BMGT, likely due to low number of subjects, and was associated with improvement in salt in all groups, and ethanol in BMS.

Characterizing Potency And Growth Properties Of Sox2-Positive Taste Epithelial Cells Using Lingual Organoid Culture
Benjamin N Tiano, Erin J Golden, Linda A Barlow
University Colorado - Anschutz Medical Campus, Aurora, CO, United States

The sense of taste guides consumption of nutrients and avoidance of toxins. Taste is accomplished when stimuli are transduced into electrochemical signals by taste receptor cells (TRCs) within taste buds. TRCs regenerate throughout life with taste perception being tightly conserved despite frequent cell turnover. Loss of this tight regulation—often a side effect of anti-cancer therapy—underlies dysgeusia (altered taste) or ageusia (loss of taste) (Ovesen et al., 1991 Clin Nutr). Recent work has uncovered the importance of the SRY-box transcription factor, SOX2, as a regulator of cell renewal. We know: (1) SOX2 is absolutely required for the renewal of TRCs (Castillo-Azofeifa et al., 2018 Dev); and (2) all types of TRCs are derived from epithelial cells expressing SOX2 (Ohmoto et al., 2017 Chem Senses). Despite the multipotent nature of SOX2-expressing cells—to date—there is no description of their potency using organoid culture technology. Intriguingly, SOX2 expression levels are highly variable in taste epithelium, and the degree to which SOX2 level correlates with multipotency is unknown. We used fluorescence-activated cell sorting of CVP epithelium from SOX2-GFP mice to collect high and low GFP+, as well as GFPneg, cell populations and assessed each group’s capacity to generate TRC-containing lingual organoids. We find cells with either high or low SOX2-GFP expression robustly generate organoids, while GFPneg epithelial cells do not. Further, we find organoids derived from differentially fluorescent SOX2-GFP populations have distinct growth behavior, proliferation kinetics, morphologies, and expression of LGR5, a known marker of taste stem cells. We are currently testing if SOX2-GFP expression level predicts organoid response to cytotoxic drugs used in cancer treatment.

Adding Vanillin To Ethanol Alters Liking But Not Perceived Burn
Jessica M. Gaby1, 2, Allison N. Baker1, 3, John E. Hayes1, 2
1Sensory Evaluation Center, The Pennsylvania State University, State College, PA, United States, 2Department of Food Science, College of Agriculture, The Pennsylvania State University, State College, PA, United States, 3Graduate Program in Neuroscience, The Pennsylvania State University, State College , PA, United States

Some reports imply vanillin interacts with TRPV1 receptors, suggesting it may modulate perception of noxious stimuli in the oral cavity. Recent work suggests pre-rinsing with vanillin may decrease capsaicin burn, which acts via TRPV1. As ethanol also activates TRPV1, here we ask if adding vanillin to ethanol may decrease perceived burn. In a series of 3 studies, participants rated the burn of ethanol with 0, 16, or 160ppm vanillin. In studies 1 (n=102) and 2 (n=82), participants wore nose clips and rated the burn of 8% and 16% ethanol (study 1) or 32% and 48% ethanol (study 2) at each vanillin concentration. In study 3 (n=65), participants were able to breathe freely (no nose clips), and rated liking and perceptual qualities (burn, sweetness, smoothness, vanilla odor and alcohol odor) for 8% and 32% ethanol solutions at the 3 vanillin levels. In all 3 studies, vanillin showed no significant effect on burn ratings at any ethanol concentration. In study 3, participants gave greater sweetness ratings for ethanol with 160ppm vanillin compared to those with 0 or 16ppm vanillin (p<.001), but vanillin did not influence ratings of burn or smoothness. Adding vanillin increased liking ratings for 8% ethanol versus the same concentration without vanillin (p=.005); this effect was not seen at 32%. These data suggest vanillin is not an efficient modulator of ethanol burn, but it may still shift hedonic responses to ethanol at ecologically relevant doses. The lowest ethanol concentration tested here, 8%, is roughly the concentration of some high gravity beers, and falls between the amount found in typical lager beers (~4.5%) and mixed drinks (~13% for a gin and tonic), suggesting added vanillin may increase perceived sweetness and liking of some lower-ethanol drinks via a burn-independent mechanism.

Response To Pleasant And Unpleasant Odors In Patients With Major Depressive Disorder
Theresa Herrmann1, Carina Köppel2, Jennifer Linn3, Ilona Croy2, Thomas Hummel1
1Smell and Taste Lab, Department of Otorhinolaryngology, Dresden, *, Germany, 2Department of Psychotherapy and Psychosomatic Medicine, Dresden, *, Germany, 3Department of Neuroradiology, Dresden, *, Germany

Background and aims: Anhedonia, the loss of the ability to experience pleasurable stimuli, is a key clinical feature of major depressive disorder (MDD). By studying the pattern of brain responses to hedonically extreme olfactory stimuli, we aimed to explore the neural mechanisms of anhedonia in MDD. Since the perception of odorous stimuli has evolved from being essential for survival to a distinct role supporting social interactions, olfactory malfunctioning can be expected to result in poor social functioning and social withdrawal. Aim of the study was to compare the processing of pleasant and unpleasant odorous stimuli in MDD patients in comparison to healthy controls. Material and methods: Using block-designed fMRI, neural responses to the smell of chocolate, lilac and tar were measured in a group of 25 patients with a history of MDD and 25 healthy controls matched for age and sex. Subjects rated the pleasantness and intensity of the presented odors. Overall olfactory performance was tested using the ‘Sniffin sticks’ kit. Depression severity and psychological disorders were screened using the German version of the Beck’s Depression Inventory, Patient Health Questionnaire, Snaith Hamilton Pleasure Scale and Childhood Trauma Questionnaire in both patients and healthy controls. Results: Preliminary results indicated a lower score for odor threshold in patients. Interestingly, ratings of MDD patients showed a strong tendency for altered perception of pleasantness, especially the smell of chocolate was perceived as less enjoyable. Conclusions: While awaiting results from fMRI analyses, behavioural data clearly indicate a different processing of pleasant and unpleasant stimuli in MDD patients which is likely to reflect changes in emotional processing.

Influence Of Different (Multi)Sensory Cues On Saliva Secretion And Composition
Paulina Morquecho Campos1, Joleen Boland1, Marieke Alblas1, Floris Bikker2, Kamran Nazmi2, Marja L Laine3, Sanne Boesveldt1
1Division of Human Nutrition and Health, Wageningen University, Wageningen, *, Netherlands, 2Department of Oral Biochemistry, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, *, Netherlands, 3Department of Periodontology, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, *, Netherlands

Exposure to (multi)sensory cues leads to anticipatory (physiological) responses as part of eating behavior. Several studies have shown an increase in saliva secretion upon (multi)sensory cues. However, little is known about their influence on saliva composition, e.g. regarding bolus formation and food digestion. Our previous research showed that exposure to single cues, i.e. macronutrient-related food odors enhanced saliva secretion but did not modify its composition. The aim of this study is to determine the influence of (multi)sensory food cues on saliva secretion and composition. We expect a more pronounced anticipatory salivary response (higher increase in Δ saliva secretion rate, pH, buffer capacity, and lower viscosity) upon food exposure while increasing sensory levels compared to control. α-amylase activity might differ between food high in starch compared to low and control. 50 normal-weight healthy participants will take part in a 4x3 cross-over design. Over 3 sessions, participants will be exposed to 12 conditions differing in level of sensory exposure (odor, odor + picture, holding real product in the mouth (odor + visual + taste), and sham feeding (odor + visual + taste + chewing)) and stimulus type (food high in starch (bread), low in starch (cucumber), and control (parafilm)). Whole saliva will be collected upon stimulus exposure by the spitting method for 5 minutes. Δ saliva secretion rate per condition will be measured by weighing the total amount and subtracting unstimulated saliva. Saliva composition will be determined by viscosity properties, pH, buffer capacity and α-amylase activity. These results will help to better understand the role of the senses, particularly chemical senses, in anticipatory responses towards healthier eating and body maintenance. 

Cross-Modal Association Between Hand-Feel Touch And Taste Cues
Han-Seok Seo, Ragita Pramudya
University of Arkansas, Fayetteville, AR, United States

Hand-feel touch cues derived from picking up food items with fingers often provide anticipatory information about oral texture perception (e.g., firmness and roughness) of such items. People are also exposed to hand-feel touch cues of non-food factors when consuming food or beverage items placed in containers or enclosed in packaging. While hand-feel touch cues are greatly involved in food/beverage perception, little attention has been paid to their association with chemosensory cues. This study (consisting of three sub-studies) aimed at determining whether hand-feel touch cues of non-food factors, in particular cup-sleeve materials can affect perception of taste solutions and brewed coffee beverages. Cup sleeves were chosen for study as the source of hand-feel touch cues because they are popularly used for both hot and cold coffee beverages and their various constituent materials are commercially available. Participants were asked to evaluate 12 different cup-sleeve materials with respect to the degree of their matching with each of basic tastes and brewed coffee-related flavor attributes. While a terry-cloth towel material was found to be more associated with sweet taste and creamy flavor, cardboard material was more associated with bitter taste and black coffee flavor. In addition, while linen material was found to be related to salty taste, silicone or stainless steel material was more associated with sour taste. It was also found that specific physical characteristics of cup-sleeve materials may mediate the cross-modal associations between hand-feel touch and taste cues, and cup-sleeve materials were found to affect perception of brewed coffee. In conclusion, this study provides empirical evidence that hand-feel touch cues can be associated with specific taste or flavor attributes.

Bitter And Sweet Taste Perception Are Reflective Of Chronic Rhinosinusitis
Noam A. Cohen1,2,3,, Ivy W. Maina1,2, Lauren R. Colquitt1, Cailu Lin1, Cowart J. Beverly1, Danielle R. Reed1
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2Dept. of Otorhinolaryngology - Head and Neck Surgery, Perelman School of Medicine at The University of Pennsylvania, Philadelphia, PA, United States, 3Philadelphia VA Medical Center, Philadelphia, PA, United States

Drawing on recent studies of taste pathways and nasal immune function, we hypothesized that bitter and sweet taste sensitivity would predict nasal symptoms. To that end, we recruited 786 adult chronic rhinosinusitis (CRS) patients with endoscopic evidence of sinonasal inflammation (mucosal edema or polypoid degeneration) or overt mucopurulence. Control subjects unselected for chronic nasal disease were recruited from community (n=377) and clinical locations (n=49) were recruited. Both the CRS patients and the control subjects were evaluated for their sense of taste (sweet, bitter, and salty stimuli, water used as control) and most subjects completed the SNOT-22 questionnaire which measures the severity of sinonasal disease. All subjects were genotyped with molecular markers (rs713598, rs10246939, rs1726866) within the TAS2R38 bitter receptor gene. Using propensity score matching for age, sex and smoking between CRS and controls, we detected significant differences between cases and controls for taste intensity ratings of sweet (sucrose, p=0.024) and bitter (PTC, p=0.032; denatonium benzoate, p=0.029; quinine, p<0.001) but not salty (NaCl, p=0.871) or water (p=0.126). Likewise, subjects with high SNOT-22 scores (more sinonasal disease) rated bitter compounds as less intense than did subjects with lower SNOT-22 score (p<0.001). Finally, cases were less likely than controls to have the taster haplotype for TAS2R38 (taster haplotype of TAS2R38; p=0.004). These results suggest that taste testing may have clinical utility in understanding chronic nasal infections and that development of taste tests with more diagnostic or prognostic potential are warranted.

Does Exposure To Continuous Indoor Fragrance Result In An Acute Impact On Health?
Cristina Jaén1, Christina Hickey2, Natalie Slickers2, Benjamin Smith3, Pamela Dalton1
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2Firmenich Inc., Princeton, NJ, United States, 3Agency for Science, Technology and Research (A*STAR), Singapore, *, Singapore

Despite a very low incidence of reported adverse safety events, concerns are often raised about the health impact of indoor fragrance, citing studies which are frequently based on self-reported outcomes and may represent an artificially high incidence of adverse effects.  To investigate this, we conducted a randomized, crossover study to evaluate potential acute effects from exposure to a test fragrance delivered using a commercially available continuous diffusion device.  Over 100 adult participants were asked to place a fragrance diffuser in their bedroom for three 1-week periods during which the machine either emitted a low or high concentration of the test fragrance or a control fragrance.  Fragrance air concentration was monitored via passive samplers.  Multiple endpoints were collected at baseline and following each week of exposure, including pulmonary function, exhaled and nasal nitric oxide, and nasal lavage for inflammatory markers.  Participants also provided fragrance intensity and symptom reports via a Survey Monkey link to enable real-time reporting of any adverse effects.  Preliminary results indicate that exposure to this fragrance did not affect pulmonary function, exhaled or nasal nitric oxide or inflammatory markers. However, the condition sequence order affected the ratings of the perceived odor intensity. This is the first study of its kind and provides insight into the impact that exposure to typical levels of continuous indoor fragrance has on consumer health.

Molecular Markers, Distribution, And Innervation Pattern Of Nasal Solitary Chemosensory Cells
Eric D Larson, Vijay R Ramakrishnan
Department of Otolaryngology, University of Colorado School of Medicine, Aurora, CO, United States

Specialized sensory cells called solitary chemosensory cells (SCCs) are scattered throughout the nasal cavity and their activation has been linked to irritant-induced inflammation in mouse models. SCCs are known to express transient receptor potential cation channel subfamily M member 5 (TRPM5), known chemoreceptors including bitter taste receptors, and the canonical taste-signaling molecules α-gustducin and phospholipase C β2 (PLCβ2). However, single cell physiology shows that not all SCCs respond to all tested ligands, suggesting a degree of heterogeneity within this population (Gulbransen et al. 2008, Lin et al. 2008). We aim to further characterize the distribution and heterogeneity of SCCs in the mouse nose. We performed immunohistochemistry on nasal sections from TRPM5-GFP and choline acetyl transferase (ChAT)-CRE/tdTomato mice to address the following: 1) which molecular marker (TRPM5, ChAT, α-gustducin, or doublecortin-like kinase-1 (DCLK1)) identifies the most SCCs, 2) are there varying degrees of innervation among SCCs, and 3) are certain markers concentrated in specific regions of the mouse nose? We find TRPM5 to be the broadest marker of SCCs. Furthermore, we observed regional differences in certain markers. For instance, α-gustducin-expressing cells were more prevalent in anterior nasal cavity, and the medial sinus had the highest density of SCCs. Lastly, we observed that SCCs in the anterior nasal cavity were more likely to be associated with a peptidergic nerve fiber (calcitonin gene-related product (CGRP)-expressing), suggesting neuronal and non-neuronal signaling mechanisms for these cells. These findings reveal heterogeneity among SCCs and suggest multiple signaling pathways within the SCC population. This work was funded by NIH 5K23DC014747-02 to VRR.

Electrophysiological Assessment Of Sensory Irritation Induced By Flavors In Electronic Cigarette Liquids In The Mouse Nasal Respiratory Epithelium
Fenge Ni, Tatsuya Ogura, Weihong Lin
University of Maryland, Baltimore County, Baltimore, MD, United States

Flavor molecules are used as a key marketing tool to promote sale and use of electronic cigarettes (e-cigs). The huge variety of flavors available at various concentrations has significantly increased world-wide use of e-cigs, especially among middle and high school students, placing these young users at the risk of nicotine addiction. However, flavor-mediated dose-dependent respiratory irritation has largely not been objectively determined. Using event-related potential (ERP) recordings from mouse anterior nasal respiratory epithelium, we assessed trigeminal activation evoked by various flavor molecules to provide an objective measurement of the sensory irritation. We recorded ERP responses to popular flavors, such as ethyl maltol in e-cigs liquids (0.5mM, each) as well as known trigeminal stimuli including nicotine (10µM), capsaicin (10µM), CO2 injected solution (pH5) and odor irritants ethyl propionate and isovaleric acid (0.5mM, each). Statistical analysis indicates that there is no difference in the response amplitude among the flavors and trigeminal stimuli (One-way ANOVA, p>0.05). These results demonstrated that e-cig liquid flavors tested can reliably evoke ERP responses, similar to various irritating and noxious substances known to stimulate the nasal trigeminal sensory system. We also monitored various flavor-induced dose-dependent ERP responses at range between 1µM and 40mM. At concentrations below 100µM, flavors generally evoked no or very small ERP responses, except cinnamaldehyde which could reliably induce an ERP about 10µM. The ERP response amplitude increased with higher concentrations of flavors applied. These electrophysiological results provide objective measurements for the potency of flavor-induced sensory irritation in the respiratory epithelium.

Sniff Inhalation With Pursed Lip Exhalation On Reflex Cough: A Randomized, Pretest-Posttest, Control-Group Study
Carolyn K. Novaleski1, Joel D. Mainland1,2, Karen Wheeler Hegland3, Paul M. Wise1, Pamela H. Dalton1
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2University of Pennsylvania, Philadelphia, PA, United States, 3University of Florida, Gainesville, FL, United States

Behavioral interventions for chronic cough focus on retraining the respiratory system, but few studies reported relevant outcome measures to support evidence-based practice. While researchers traditionally elicited reflex cough with aerosolized capsaicin and citric acid, these stimuli are not optimal for clinical populations with heightened responses. Here we randomized 60 healthy male and female adults (18-35 years) to an intervention group that performed sniff inhalation with pursed lip exhalation or control group that performed deep, relaxed nasal inhalation and exhalation. Pre- and post-randomization, participants performed a single breath inhalation test to elicit reflex cough using ethyl butyrate diluted in paraffin oil delivered through a face mask connected to an olfactometer and respiratory pneumotachograph at 20, 40, and 60% v/v, with order of concentration randomized. Digitized airflow waveforms revealed that cough was significantly associated with group assignment (χ2=8.50, p<.01). Participants in the intervention group were less likely to cough compared to those in the control group. Peak expiratory airflow rate, peak expiratory flow rate rise time, mean expiratory airflow, and cough expired volume significantly decreased in the intervention versus control group (p<.05). Sensation of urge-to-cough, measured using a general Labeled Magnitude Scale, significantly reduced posttest compared to pretest (F=13.91, p<.001), but was not significantly different between the intervention and control groups (F=0.05, p>.05). Our work indicates that ethyl butyrate is a cough-inducing volatile chemical stimulus. Because airborne stimuli (e.g., odors, chemicals) are associated with chronic cough, the current paradigm offers a stimulus more typical of compounds encountered during everyday exposures.

Impact Of Solitary Chemosensory Cells And Trpm5 On Murine Airway And Intestinal Microbiota
Vijay R. Ramakrishnan1, Jennifer M. Kofonow2, Thad Vickery1, Eric D. Larson1, Catherine B. Anderson1, Daniel N. Frank2
1Department of Otolaryngology, University of Colorado School of Medicine, Aurora, CO, United States, 2Division of Infectious Disease, University of Colorado School of Medicine, Aurora, CO, United States

The human microbiome is increasingly recognized as a contributor to health and disease. Large interpersonal variability has been observed in studies of the human airway microbiome and can be partially attributed to differences in diet and environmental influence. However, host factors governing microbial colonization are of significant interest. Nasal solitary chemosensory cells (SCCs), and their lower airway and gut homologues (brush and tuft cells, respectively), have been recently observed to exhibit numerous immune properties. These cells are defined by their expression of Transient Receptor Potential Cation Channel Subfamily M member 5 (TRPM5) and require the transcription factor Skn-1a/Pou2f3 for development. In the present study, we examined upper airway and gut microbiota colonization in TRPM5-deficient and Skn-1a/Pou2f3-deficient mice using 16S rRNA gene sequencing. Immunohistochemistry and PCR were used to document the presence or absence of tissue-specific expression of TRPM5 and chemosensory markers in knockout and wild type mice. In gut, we found alterations in several bacterial taxa. TRPM5-deficient mice exhibited more Firmicutes and less Proteobacteria and Candidate-Division-TM7 at the phylum level, and less Helicobacter at the genus level. Skn-1a/Pou2f3-deficient mice were colonized with more Proteobacteria. In the nasal cavity, substantially lower bacterial biomass was recovered, limiting statistical comparisons. This study supports the immune regulatory capability of SCCs, indicates a role for chemosensory pathways in regulation of microbiota colonizing luminal surfaces, and suggests that SCCs may do this using TRPM5-independent pathways in addition to canonical taste transduction.    Funded by NIDCD K23DC014747 (VRR)

Differences In The Microbiota Of The Olfactory And Respiratory Epithelia
Melissa Singletary, Henri Alexandre Giblot Ducray, Ludmila Globa, Oleg Pustovvy, Edward E. Morrison, Vitaly Vodyanoy, Iryna Sorokulova
Department of Anatomy, Physiology, and Pharmacology, Auburn University College of Veterinary Medicine, Auburn University, AL, United States

The impact of the microbiota on immunity and overall health are well documented. Most studies focused on the microbiota of the gastrointestinal tract, oral cavity, respiratory system, and integument. The olfactory organ was recently shown to be influenced by the microbiota, as germ-free mice had alterations in olfactory epithelial development and function. Most studies evaluating the nasal microbiota utilize swabs to sample the rostral nasal passages and are not expected to adequately represent the olfactory microbiota. The goal of this study was to evaluate the microbiota of the individual microenvironments in the nasal cavity to represent the olfactory epithelia, sampled as the ethmoid and main olfactory epithelium, separately from the respiratory epithelium. Aseptic technique was used for microsurgical removal of the respiratory, ethmoid, and main olfactory epithelium individually for microbial DNA extraction and 16s rRNA gene sequencing. On the phylum level the results showed a unique bacterial population of the olfactory epithelia having a relative abundance significantly higher in the ethmoid epithelium (56.4%±20.5%) compared to the respiratory epithelium (0.9 %±0.3%). The predominant identified phyla across samples included Firmicutes and Proteobacteria with a significantly higher representation of Firmicutes in the respiratory epithelium (97.8%±1.2%). On the genus level the results of identified bacteria showed that 78.2% of microbiota was shared between the three epithelia, while 21.8% was significantly different. The results suggest the olfactory epithelia contains a unique microbiota with distinctions from the respiratory epithelium of the nasal cavity, most significantly with the ethmoid epithelium. Further identification and functional olfactory studies are needed.

Camsap3 Hypomorphs Exhibit Abnormal Mucin Clearance And Olfactory Dysfunction
Jing Zheng, Alan M. Robinson, Satoe Takahashi, Robert C. Kern
Department of Otolaryngology - Head and Neck Surgery, Feinberg School of Medicine. Northwestern University, Chicago, IL, United States

CAMSAP3 is a microtubule (MT)-minus-end regulator. Our data show that CAMSAP3 is expressed in multiciliated cells and olfactory sensory neurons in nasal cavity. Both cells carry multiple cilia composed of MTs in ‘9+2’ configuration in their axoneme: 2 central singlet MTs surrounded by 9 MT doublets. One of the long-standing questions is how the central MT pair is assembled, as they are not continuous with MT triplets in the basal body as surrounding 9 MT doublets do. We hypothesize that CAMSAP3 is involved in building such a structure. Hence, we investigated global CAMSAP3 knockdown mouse model, Camsap3tm1a, created by the “knockout-first” conditional allele targeting strategy. Due to fertility issues, we re-derived this model in FVB and CBA/CaJ strain backgrounds. All Camsap3tm1a homozygotes, regardless of the sex, age, or strain background, failed a behavioral test used to evaluate olfactory function. Anatomical examination revealed complete obstruction of the nasal passage, thinning of the epithelial layer, and degeneration of olfactory sensory neurons. In addition, our data show that Camsap3tm1a mice exhibit multiple pathological phenotypes associated with primary ciliary dyskinesia including female subfertility, anosmia, rhinitis, sinusitis, and otitis media with effusion. Multiciliated cells of Camsap3tm1a mice lose coordinated back-and-forth motion of cilia needed to generate a directional flow for mucin clearance, resulting in defects in mucociliary transportation. Unlike wildtype, cilia from Camsap3tm1a mice lack CAMSAP3 at the transition zone where central MT pairs are initiated. Indeed, a majority of cilia from Camsap3tm1a mice lack central MT pairs. Together, our data suggest that CAMSAP3 is required for forming central MT pairs and indispensable for olfaction.

Sensory And Survey Designation Of Sweet Liking Contribute To Diet Quality, Adiposity And Blood Pressure Relationships In Adults
Bruce E. Blanchard, Brittany A. Larsen, Jeanne M. McCaffery, Valerie B. Duffy
Dept of Allied Health Sciences, University of Connecticut, Storrs, CT, United States

Background: Chemosensation has been connected with health by influencing food/beverage liking and ultimately consumption. We examined measures of sweet liking/disliking, diet healthiness (diet quality) and anthropometrics in a lab-based study. Methods: A convenience sample of reportedly healthy adults (n=75, ages 25-63, 49 females) were characterized as 39 sweet likers and 33 dislikers from the slope of hedonic response to sampled 5%, 10% and 20% aqueous sucrose. On a validated survey, subjects reported the degree of liking/disliking of foods and beverages, which were organized into reliable food groups, and then into a valid diet quality index (DQI). From measurements, 31% were overweight and 15% obese by body mass index (BMI) and 32% had borderline hypertension. Results: In analysis of covariance (ANCOVA), controlling for age and sex effects, sweet likers had significantly lower DQIs than did dislikers, which was driven by significantly less liking for vegetables, fiber, and low-fat proteins among sweet likers. Sweet likers versus dislikers were not significantly different in reported liking for sweet foods or drinks. In multiple regression analysis, sweet likers versus dislikers did not vary significantly in BMI. However, those who survey reported greater liking for sweet foods and beverages had significantly higher BMI and those with higher DQI had lower BMI. In ANCOVA, sucrose likers had greater systolic blood pressures (SBP), independent of BMI. In path analysis, some of the association between lower DQI and greater SBP was mediated by greater BMI. Summary: Sensory-based versus survey-based designation of sweet liking produced different associations with diet healthiness, adiposity and blood pressure. Both contribute uniquely to understanding chemosensory relationships with diet and health.

Isocaloric Pair-Feeding With A Fatty Diet Prevents Weight Gain But Not Disruption Of Olfactory Anatomy
Brandon Chelette, Debra Fadool
Florida State University, Tallahassee, FL, United States

Consumption of a fatty diet causes mice to gain weight and adipose tissue. Maintenance on a fatty diet also causes a loss of olfactory sensory neurons (OSNs). It is unclear whether the disruption of the olfactory system is driven by the diet itself or by the resulting weight gain. Transgenic mice with a reporter for M72 (Olfr160) were challenged with a moderately-high fat diet (MHF; 32% fat) both ad libitum and in a pair-feeding format. Two treatment groups were allowed ad lib access to either the MHF (AL-MHF) or a control diet (AL-CF; 13.5% fat). Two pair-fed treatment groups were provided with either the MHF (PF-MHF) or the CF diet (PF-CF), but their daily food allotment was calorically equivalent to the consumption of an AL-CF mouse. After 6 months, male AL-MHF mice weighed significantly more and had significantly higher adiposity than all other treatment groups (F(3,18)=17.1, p<0.0001; F(3,18)=10.1, p<0.0001). Both the AL-MHF and PF-MHF exhibited a significant reduction in OSN projections (F(3,18)=14.2, p<0.0001) even though the PF-MHF were unable to over consume the MHF diet and exhibited the same bodyweight and adiposity as the CF fed mice. Similar trends were found in females though not statistically significant; both the AL-MHF and PF-MHF groups displayed reduction of OSN projections (F(3,19)=2.8, p=0.06) even though neither group gained bodyweight or adiposity compared to CF-fed controls (F(3,20)=1.9, p=0.16; F(3,20)=1.2, p=0.34). Male and female AL-MHF mice displayed a reduced ability to clear glucose compared to the CF-fed groups while PF-MHF mice displayed an intermediate ability (Males: F(3,18)=4.7, p = 0.013; Females: F(3,20)=5.4, p = 0.007). These results suggest that the long-term macronutrient imbalance via the MHF diet is driving anatomical loss in the olfactory system.

Chemical Ablation Of Olfactory Sensory Neurons Causes Anosmia, Neuronal Cell Death, And Systemic Metabolic Changes
Destinee/N. Gatlin1, Henal/N. Sutaria1, Nimmi/D. Patel1, Abigail Perkins1, Brandon/M. Chelette1, 2, Ashley/M. Loeven1, Debra/A. Fadool1,2,3
1Department of Biological Science, Florida State University, Tallahassee, FL, United States, 2Program In Neuroscience, Florida State University, Tallahassee, FL, United States, 3Institute of Molecular Biophysics, Florida State University, Tallahassee, FL, United States

Obesity affects around 70 percent of Americans. However, the connection between the role of the olfactory system and the onset of obesity is not understood. Based on previous research performed in the laboratory, it was found that diet-induced obesity leads to inadequate functioning of the olfactory sensors in detecting chemosensory cues. We wanted to examine if this finding was birectional - what might happen to metabolism if we disrupted olfaction by ablating olfactory sensory neurons (OSNs)?  OSNs were chemically ablated by intraperitoneal injection of the drug methyl bromide (MeBr). The buried cookie assay confirmed anosmia following drug treatment.  Mice were placed in a CLAMS metabolic chamber (Columbus Instruments) to quantify systems physiology metrics in line with their loss of smell. We hypothesized that induction of anosmia would decrease metabolic energy expenditure similar to that found in obese mice that also lose their sense of smell. We found that MeBr-treated mice significantly decrease consumption of oxygen (VO2) in the dark cycle.  We imaged the loss of OSNs in OMPgfp mice following MeBr treatment using a Zeiss LSM 880 confocal microscope. The number of OSNs per 100 um was significantly less in MeBr-treated mice (39 + 0.4 (saline) vs. 0.2 + 0.2 (drug); Student’s t-test, n=4 mice each).  We then used fluorescence microscopy (Zeiss Axiocam camera and Axiovision software) to acquire measurements of the thinning OSN layer following ablation.  In conclusion, the combined loss of OSNs and inability to smell was correlated to a reduced metabolic expenditure in the dark cycle without a change in daily food consumption (caloric intake). Our results may help understand how the healthy olfactory system balances our energy expenditure to prevent unwanted weight gain or obesity. 

The Mechanisms Of The Enhancement Of Energy Metabolism By Amg517, A Trpv1 Antagonist In Mice
Jun Hai1, Fuminori Kawabata2, Yuko Kawabata3, Shotaro Nishimura1, Shoji Tabata1
1Laboratory of Functional Anatomy, Faculty of Agriculture, Kyushu University, Fukuoka, *, Japan, 2Physiology of Domestic Animals, Faculty of Agriculture and Life Science, Hirosaki, *, Japan, 3Section of Oral Neuroscience, Graduate School of Dental Sciences, Fukuoka, *, Japan

Transient receptor potential vanilloid 1 (TRPV1) is a nociceptive cation channel activated by heat, protons and chemical ligands such as capsaicin.  We have investigated the roles of TRPV1 in the modulation of energy metabolism in vivo.  Although, it has been reported that the activation of TRPV1 by its agonists enhances energy metabolism, we previously revealed that the inhibition of TRPV1 by its antagonists also enhanced energy metabolism in mice.  However, its mechanisms remain unclear.  The aim of this study is to explore the mechanisms underlying the enhancement of energy metabolism by TRPV1 antagonist in mice.  We used AMG517 as TRPV1 antagonist.  Both oral and intraperitoneal administrations of AMG517 enhanced energy metabolism.  In the mice desensitized to afferent sensory nerves expressing TRPV1 by pretreatment of capsaicin, oral administration of AMG517 did not change energy metabolism.  Next, to clarify the involvement with the sympathetic nervous system, we investigated the effect of propranolol, a β-adrenoceptor antagonist, on the enhancement of energy metabolism by AMG517.  Pretreatment of propranolol partially suppressed the enhancement of energy metabolism by oral administration of AMG517.  On the other hand, pretreatment of propranolol almost abolished the enhancement of energy metabolism and locomotor activity level by intraperitoneal administration of AMG517.  These results suggested that oral administration of TRPV1 antagonist enhanced energy metabolism via afferent sensory nerves including vagal nerves, and intraperitoneal administration of TRPV1 antagonist enhanced energy metabolism by increasing the sympathetic nerve activity and the locomotor activity in mice.

A Pilot Study On The Effects Of Metabolic Surgeries On Flavor Perception 2-5 Years Post-Surgery
Katie Nance1, Charmi Patel2, Blair Rowitz3, M. Yanina Pepino1
1Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 2Department of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 3Carle Hospital, Urbana, IL, United States

Metabolic surgeries, like Roux-en-Y gastric bypass (RYGB) and Sleeve gastrectomy (SG), are the most successful long-term treatment for obesity and its associated comorbidities. The success of these surgeries may partially be due to the profound effect these surgeries have on taste preferences. Patients report changes in taste and smell (hereafter referred to as flavor) after metabolic surgeries; however, few studies have measured these changes using validated sensory techniques. In addition, it is unknown whether these changes last beyond one year after surgery.  We tested flavor perception in 6 subjects before metabolic surgery (BMI= 47.0 ± 10.3 kg/m2), 6 subjects who underwent SG surgery 2-5 years ago (BMI= 30.4 ± 9.8 kg/m2) who lost 35.4±19.0% of pre-surgery weight, and 14 gender and age matched subjects with a normal BMI (22.7 ± 1.5 kg/m2). Participants rated food-like stimuli for perceived intensity of sweet, salty, sour, bitter, savory, and creaminess using the generalized Labeled Magnitude Scale. To determine the effect of surgery on retronasal smell, subjects rated the stimuli with and without nose clips. We found that participants in the post-surgery group experienced a greater enhancement of sweetness in pudding and of sourness in high-citric acid “lemonade” via retronasal smell than pre-surgery and normal weight subjects (P≤0.05).  We also found that, consistent with our previous findings at 1-year post-RYGB/SG surgery, participants 2-5 years post-surgery experienced repetitively tasting sucrose as mostly “unpleasant”.  Our preliminary results suggest that metabolic surgeries might affect flavor perception by changing retronasal smell perception and that changes in sweet liking found 1 year after surgery last 2-5 years later. 

Effects Of Gastric Vagotomy On Taste Responses In The Nucleus Of The Solitary Tract In Awake Freely Licking Rats.
Flynn P. O'Connell1, Michael S. Weiss1, Andras Hajnal2, Krzysztof Czaja3, Patricia M. Di Lorenzo1
1Binghamton University, Binghamton, NY, United States, 2The Pennsylvania State University, College of Medicine, Hershey, PA, United States, 3University of Georgia, Athens, GA, United States

Currently, the most effective form of weight-loss is bariatric surgery (Adams et al. 2017; PMID: 28930514), e.g. Roux-en-Y gastric bypass. This type of surgery results in the transection of vagal afferents, producing synaptic reorganization of central gustatory structures including the nucleus of the solitary tract (NTS; Ballsmider, et al. 2015. PMID: 25722893). The aim of the present study was to characterize taste response profiles of neurons in the NTS in diet-induced obese (DIO) rats following gastric (VgX) or sham vagotomy (SHAM). Rats were initially placed on a high fat diet (60% kCal from fat) for 6 wks before undergoing VgX. Once recovered, rats were implanted with a 16-channel drivable electrode. Rats were moderately water deprived and placed in an operant chamber where they could lick tastants from a spout. Tastants were presented for 5 consecutive licks separated by 5 licks of artificial saliva (AS) on a variable-ratio 5 schedule. Tastants (dissolved in AS) were: sucrose (0.1M, 0.5M, 1M), NaCl (0.05M, 0.1M), citric acid (0.01M), quinine HCl (0.0001M), 25% heavy cream, 25% heavy cream (dissolved in 0.5M sucrose), 0.5M sucrose + 0.1M NaCl, 0.1M MSG + 0.01M IMP, and AS. Preliminary results were obtained from 11 taste-responsive cells in VgX rats and 5 taste-responsive cells in SHAM rats. Taste responses in VgX rats were significantly larger than those in SHAM controls, F(1,83)=13.54, p=0.004. Taste response latencies and durations did not differ between cells in VgX and SHAM rats. Analyses of temporal coding showed that neurons in VgX and SHAM rats conveyed less information about taste quality than neurons in lean rats.  These data suggest that the effects of a HFD on the neural representation of taste in the brainstem are only partially ameliorated by gastric vagotomy.

Salt And Spice And Everything Rice: Taste-Odor-Trigeminal Interactions In A Rice Matrix
Molly R. Spencer, Pamela H. Dalton
Monell Chemical Senses Center, Philadelphia, PA, United States

There is a critical need to develop strategies to combat the current obesogenic food environment; one approach is to increase the perception of salt by adding a trigeminal stimulus to increase the complexity and dimensionality of flavor. Flavor interaction studies based on solution or air stimuli may not reflect the true flavor impression perceived during the eating experience. In this study, we investigated flavor interactions in a rice matrix, hypothesizing that adding spice would increase the perception of salt and flavor complexity. Subjects (n=40) were served 17 rice samples in triplicate. The samples contained varied levels of 3 flavor components: a taste stimulus (NaCl), an odor stimulus (non-spicy bell pepper powder), and a trigeminal stimulus (cayenne pepper).  A blind replicate was evaluated with and without retronasal olfaction. The subjects used the general Labeled Magnitude Scale (gLMS) to rate intensity of saltiness, spiciness, and flavor complexity. Our hypotheses were supported; spiciness enhanced the perception of saltiness, and bell pepper flavor increased the perception of both spiciness and saltiness. Interestingly, increased salt content delayed and suppressed the perception of spiciness.  Although both cayenne pepper and bell pepper flavor increased perceived flavor complexity, the trigeminal impact was more effective than the odor stimulus. Blocking retronasal odor both delayed and suppressed spice perception, supporting the notion that the trigeminal and olfactory systems function closely together. Overall, these findings support the potential of congruent trigeminal‑induced taste enhancement, similar to the previously established concept of odor-induced taste enhancement, and these may be useful strategies for dietary enhancements to promote satisfaction and satiation.

Olfactory Identification And Sensitivity In Wolfram Syndrome
Raul Alfaro1, Tasha Doty2, Anagha Narayanan2, Tamara Hershey2, M.Yanina Pepino1
1University of Illinois, Urbana, IL, United States, 2Washington University, St. Louis, MO, United States

Objective: Wolfram Syndrome (WFS) is a rare genetic disease typically characterized by insulin dependent diabetes mellitus, vision and hearing loss. The majority of people with WFS also develop other neurological problems, including loss of sense of smell. The aim of this study was to assess the extent to which olfactory dysfunction in WFS is explained by decreased olfactory sensitivity (i.e. peripheral elements) or smell identification impairment (i.e. higher cognitive centers). Methods: 40 subjects with WFS (13.5±5.6 yrs.), 25 healthy controls (HC; 14.6±5.2 yrs.) and 19 subjects with T1DM (14.6±4.9 yrs.) were evaluated at Washington University from 2010-2017. We assessed 1) olfactory sensitivity by using Sniffin’ Sticks for butanol detection thresholds and considered an olfactory threshold dilution level <5.5 as indicative of impairment, and 2) olfactory identification with the University of Pennsylvania Smell Identification Test (UPSIT), and used scores from normative data (age and sex adjusted) to consider a percentile ≤5 indicative of anosmia. Results: Detection thresholds for subjects with WFS were not significantly different to HC and T1DM groups (P=0.09), although 18% of subjects with WFS and 28% of subjects with T1DM, but none of HC subjects, had detection thresholds for butanol ≤5.5. UPSIT scores were significantly lower in WFS than the control groups (WFS=25.3±7.5, HC= 30.4±6.1 and T1DM=33.0±4.4; P<0.001). Fifty three percent of subjects with WFS had an UPSIT score ≤5 percentile compared to 20% and 11% of HC and T1DM, respectively (P<0.005). Conclusion: Our results suggest that marked impairment in olfactory identification observed in WFS is not secondary to olfactory insensitivity or diabetes, but instead relates to central dysfunction.

Comparisons Of Three Different Methods To Assess Trigeminal Sensitivity​
Benoît Jobin1,2, Cecilia Tremblay3, Fanny Lecuyer Giguère1,2, Johannes Frasnelli1,2,3
1Université de Montréal, Montréal, QC, Canada, 2Centre d'études avancées sur la médecine du sommeil de l'Hôpital du Sacré-Coeur de Montréal, Montréal, QC, Canada, 3Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada

The trigeminal system conveys sensations such as the freshness of eucalyptus or the spiciness of pepper. The lateralization task, which consists in identifying the stimulated nostril in a monorhinal paradigm, is possible only if there is stimulation of the trigeminal system. Thus, it is with a lateralization task that we can assess the sensitivity of trigeminal system. The purpose of this study is to compare three different ways to administrate the lateralization task using eucalyptol as a stimulus: 1. a gold standard method consisting of 40 constant stimuli of 0.5s ; 2. a shorter version of 20 stimulations ranging from 0.2 to 0.6s ; 3. an automatized staircase method in which the test adjusts the stimulation time according to the participant's responses. To this end, we asked 32 young and healthy subjects aged between 18 and 35 to perform the three versions of the lateralization task. In order to examine the effectiveness of these different methods to discriminate young adults from older ones, another group of 16 older participants aged 55+ was compared to the younger group. Based on the success rate, we found that only the gold standard method revealed a significative difference between older and younger participants. The other methods did not seem as effective in assessing trigeminal sensitivity. However, more participants are needed to draw conclusions.

Evaluation And Evolution Of The Olfactory Dysfunctions Within 24 Hours After A Mild Traumatic Brain Injury (Mild Tbi)
Fanny Lecuyer Giguere1,2,3, Andreas Frasnelli4, Elaine de Guise1,2,5, Johannes Frasnelli1,3,6
1Department of Psychology, University of Montreal, Montreal, QC, Canada, 2Centre de recherche interdisciplinaire en réadaptation du Montréal métropolitain (CRIR), Montreal, QC, Canada, 3Hôpital du Sacré-Cœur de Montréal, Montreal, QC, Canada, 4Emergency Department, Spitalzentrum Oberwallis, Visp, *, Switzerland, 5Research Institute-McGill University Health Centre, Montreal, QC, Canada, 6Department of Anatomy, Université du Québec à Trois-Rivières (UQTR), Trois-Rivieres, QC, Canada

Objective: This study aimed to evaluate olfaction 24 hours (baseline) and one year (follow-up) after a mild traumatic brain injury (TBI). We further evaluated the influence of the cognition and affective state on olfactory function. Method: At baseline, olfactory function, neuropsychological and affective state were assessed in 42 patients (20 mild TBI; 22 orthopedic injury). At follow-up, 12 patients with mild TBI and 7 controls could be included and we assessed olfactory function, affective states and post-concussion symptoms.  Results: At baseline, patients with mild TBI demonstrated significantly reduced olfactory function, compared to controls, with more than 55% of the patients presenting sings of hyposmia. At follow up, no significant differences in olfactory scores between cases and controls were observed. However, patients with mild TBI who had exhibited hyposmia at baseline exhibited significantly higher anxiety levels and more post-concussion symptoms than patients with mild TBI with normal olfactory function at baseline. Conclusions: In the acute phase of mild TBI a majority of patients has impaired olfactory function. Further patients with olfactory dysfunction are more likely to exhibit post-concussion and anxious symptoms at follow-up. Olfactory testing in the acute phase may therefore serve as a screening tool for long term outcome.

The Impacts Of Aging And Military Service On Olfactory And Taste Function
Melissa H W Wong, Alexa J Pullicin, Juyun Lim
Oregon State University, Corvallis, OR, United States

Much of what is known about human aging is based on the World War II generation. Given that a significant portion of men in this cohort served in the military, military service is a hidden variable in aging literature. The primary goal of this study is to understand the impact of military service on olfactory and gustatory function of veterans. More specifically, we investigate the impacts of aging, exposure to warzones, and their interactions on possible deterioration of sensory functions of veterans. Older individuals (> 60 years) who had served in the military were recruited. These individuals were relatively healthy, nonsmokers with no history of PTSD. Civilians of similar health status, age, gender, education, and income level were also recruited. Olfactory function was assessed using the Sniffin’ Sticks method, which includes standardized threshold, discrimination, and identification tasks. Results of the olfactory function test were summed to obtain an overall TDI (Threshold, Discrimination, Identification) score. Taste function was assessed by performing discrimination and identification tasks for four basic tastes (sweet, salty, sour, bitter). Our preliminary findings suggest that veterans had lower TDI scores compared to their civilian counterparts. More studies are currently underway to further test the impact of warzone exposure on the sensory functions of veterans.

Higher Level Of Expression Of Transcripts Involved In Inflammation And Immunity In Trpm5-Gfp Olfactory Sensory Neurons
Brooke D Baxter1, Eric Larson2, Vijay Ramakrishnan2, Kenneth Jones3, Paul Feinstein4, Joel D Mainland5, Diego Restrepo1
1Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States, 2Department of Otolaryngology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States, 3Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States, 4Hunter College, City University of New York, New York, NY, United States, 5Monell Chemical Senses Center, Philadelphia, PA, United States

A subset of olfactory sensory neurons (OSNs) express the transient receptor potential cation channel M5 (TRPM5). The role of this subset of neurons is currently unknown. We previously showed that a subset of TRPM5-expressing OSNs respond to semiochemicals and that these responses are decreased in TRPM5 knockout mice (Lopez et al. J. Neurosci. 34:3268, 2014). To further characterize this subset of cells, we carried out RNA sequencing in OSNs using a line of adult mice where the TRPM5 promoter drove GFP expression and the olfactory marker protein (OMP) promoter drove nuclear-targeted mCherry expression. With these reporters, we then used flow cytometry to sort mature OSNs from microvillar cells and identify the subset of TRPM5 expressing cells. When examining mature OSNs, we found that the subset of cells expressing TRPM5 had elevated expression of 18 olfactory receptor (OR) transcripts. These OR transcripts were not expressed in the microvillar cells. Gene ontology analysis revealed that the TRPM5+ cells express elevated levels of transcripts related to immunity and inflammation. Finally, the abundance of TRPM5-expressing cells decreased when mice were housed in high ventilation cages. Our findings suggest that expression of TRPM5 in OSNs varies depending on environmental conditions and that these neurons may be involved in inflammatory or immune responses of the OE, an established venue for viral infection of the central nervous system. We are characterizing the responsiveness of these ORs to semiochemicals and infection.

Social Odor Context Enhances Encoding And Recognition Of Faces
Cinzia Cecchetto1,2, Florian Ph.S Fischmeister1, Sarah Gorkiewicz1, Deepika Bagga1,2, Valentina Parma3,4,5, Veronika Schoepf1,2
1Institute of Psychology, University of Graz, Graz, *, Austria, 2BioTechMed, Graz, *, Austria, 3SISSA – International School for Advanced Studies, Neuroscience Area, Trieste, *, Italy, 4William James Center for Research, ISPA - Instituto Universitário, Lisboa, *, Portugal, 5Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, *, Sweden

Olfactory stimuli have been shown to be able to increase memory performance when the same odor is presented during both the encoding and the recognition phases. Among olfactory stimuli, social odors (called also human body odors or chemosignals) are known to be able to transfer socially relevant information: even when not consciously perceived, body odors are able to carry different types of social information regarding individuals’ identities (e.g., age, gender, health status, sexual availability) and personal predispositions. To investigate whether social odors enhance the encoding and recognition of social visual stimuli, such as faces, we have conducted an fMRI study in which 36 healthy women performed an encoding and recognition memory task on female faces during which a neutral fragrance (masker) or a female social odor masked by the same masker (masked social odor) were presented as contextual cues.
At the behavioral level, results show that participants are faster in recognizing faces when they are presented paired with the masked social odor compared to the masker. At the neural level, when faces are successfully encoded in the presence of the masked social odor, compared to masker odor, significant activations increase in areas related to social cognition (angular gyrus), odor perception (anterior insula and orbitofrontal cortex), and episodic memory (caudate nucleus). These results suggest that the two types of social information (face and social odor) were integrated together and this integration made participants faster in the subsequent recognition.    

Effect Of Environmental Estrogens On Crayfish Aggressive Behavior
Paige westra, Jake Radke, Jenne M. Westberry, Kurt R. Illig
University of St. Thomas, St. Paul, MN, United States

Crayfish establish social dominance hierarchies through agonistic interactions including fighting and aggressive behaviors. These behaviors are regulated by chemical signals detected by olfactory sensors on the antennules, aesthetasc sensilla. Estrogens play a role in social interactions between organisms, posing a potential issue given the increase in estrogen concentrations in the world's water supply. Crayfish have a permeable perineurium, which forms the blood-brain interface, allowing environmental estrogen to directly impact the nervous system. The present studies were designed to test the effect environmental estrogens on crayfish, Procambarus clarkia. Crayfish were housed low (100 mg/ liter) or high (10000 mg / liter) estrogen or normal water without estrogen. We recorded several aggressive behaviors including rearing, cornering, meral spread, wrestling and clawing. Behavior was monitored for 10 minutes in two different paradigms: “mirror test” (crayfish alone in and responding to own reflection) or “conspecific test” (crayfish tested with another size and sex-matched conspecific). All animals exposed to either dose of estrogen had significantly increased aggressive behavior. To determine the direct impact of environmental estrogens on chemical communication, we removed sensilla prior to testing.  Removal of sensilla only influenced aggressive behavior in conspecific test where there as a decrease in aggressive behavior in the control and low estrogen groups. Interestingly, removal of sensilla did not decrease aggressive behavior in the high estrogen group, suggesting an interaction between olfactory chemical information and hormones in the environment. Our data provide evidence that environment estrogens can influence social behavior in a dose-dependent manner.  

The Role Of Accessory Olfactory Bulb External Granule Cells In Chemosensory Information Processing
Xingjian Zhang, Julian Meeks
UT Southwestern, Dallas, TX, United States

Rodent social behavior relies heavily on the accessory olfactory system (AOS), an olfactory pathway best known for detecting pheromones. The accessory olfactory bulb (AOB) is the first and only dedicated circuit for AOS information processing, and information produced by the AOB powerfully influences social and reproductive behaviors. The local circuit in the AOB comprises projecting mitral cells (MCs) and several classes of local GABAergic interneurons. The role of inhibitory interneurons in sculpting MC activity is mostly unclear. I am using ex vivo electrophysiology and Ca2+ imaging to study how several classes of AOB interneurons, including a novel population called external granule cells (EGCs), respond to pheromone stimulation and influence MC activity.
Two-photon Ca2+ imaging indicates that EGCs, which previous experiments showed are extremely hyperpolarized at rest, respond very sparsely to monomolecular pheromones that robustly activate MCs. However, EGCs robustly responded to natural pheromone-containing substances (dilute mouse urine and fecal extracts). Compared to AOB MCs and other classes of AOB interneurons, the sparse responses of EGC indicate that these cells are only engaged during conditions in which many unique pheromones are simultaneously encountered. Ex vivo targeted whole cell patch clamp recordings revealed broad monomolecular-ligand-evoked subthreshold activity of these cells, indicating that EGCs are broadly innervated by MCs, but possess extremely high thresholds for activation. AOB EGCs are thus well-positioned to perform global MC suppression in specific real-world conditions involving rich pheromone environments, a function that is likely to have important consequences for mouse social behavior.  

Collection Method Alters Observed Concentration Of Salivary Proteins Important To Oral Sensation
Lissa Davis, Cordelia Running
Purdue University, West Lafayette, IN, United States

Salivary proteins affect oral sensations. For analysis, saliva is typically collected and centrifuged cold to prevent formation of mucin gels, which form un-pipette-able masses at room temperature that can trap other proteins or molecules of interest. We hypothesized that collecting and processing saliva at warmer temperatures might prevent mucin gels and keep the saliva in a state similar to oral conditions. We thus prepared human saliva for total protein and LC/MS-MS proteomic analyses using the following four combinations of collection (temperature at which the tube was held prior to centrifugation) and centrifugation conditions: warm (37°C)/warm; room temperature (21°C)/warm; cold (4°C)/cold; and flash frozen (-80°C)/cold. Saliva was collected from a single individual who rinsed with 3mL 0.5% citric acid for 2 minutes, after which the expectorated sample+saliva was immediately aliquoted to the different temperature conditions. Each condition was analyzed in triplicate. Results showed total protein concentrations from the BCA assay were significantly higher from warm vs. cold conditions. However, individual proteins follow different patterns. Proline rich proteins 27 and 4 as well as Mucin 7 (implicated in texture and/or taste) were generally higher from cold vs. warm conditions (p=0.0001, p=0.042, p=0.011). However, carbonic anhydrase 6 (“gustin,” important for taste) levels were higher in warm conditions compared to cold (p=0.044).  Thus, optimum preparation conditions may differ across different salivary proteins, and absolute protein concentration may not predict the behavior of individual proteins from proteomics preparations. Researchers should consider these potential confounding factors when designing studies and analyzing data regarding salivary proteins.

Person-To-Person Differences In The Liking And Saltiness Of 256 Mm Sodium Chloride Are Due In Part To Genetics
Cailu Lin, Lauren Colquitt, Danielle Reed
Monell Chemical Senses Center, Philadelphia, PA, United States

Saltiness, like sweetness, is an attractive taste quality but people differ in how much added salt is ideal in particular foods. Here we explore the relationship between salt intensity and liking, and whether individual differences are determined by each person’s unique experience or unique genome. To that end, we asked 1108 human twins (monozygotic, MZ=911, dizygotic, DZ=197) to rate 256 mM sodium chloride for liking and saltiness. Subsets of twins also rated a lower concentration of sodium chloride (128 mM; N=192) and other non-sodium salts (201 mM potassium chloride, N=768; 135 mM calcium chloride, N=187; and 89 mM cesium chloride; N=157). We computed the heritability of liking and saltiness by comparing the similarity of MZ and DZ twins using variance partitioning models and reported it as h2, which can range from zero (no evidence of genetic effects) to 1.0 (all person-to-person differences are completely due to genotype). The most heritable of the known taste traits is the bitterness of PTC which was included here for comparison. Heritability was moderate for liking of 256 mM sodium chloride (h2=0.34) and lower for rating of saltiness (h2=0.20). This pattern of liking being more heritable than saltiness was true for the lower concentration of sodium (h2=0.33 vs 0.14) and calcium chloride (h2=0.34 vs 0.13) but not for potassium chloride (h2=0.27 vs 0.29) or cesium chloride (h2=0.06 vs 0.41). For comparison, heritability for the bitterness of 180 µM PTC was 0.66. The perception of saltiness for a range of salts is at least partially determined by genotype and these genetic studies pave the way to find genotypes that contribute to the liking for high-salt foods.

Saccharin Supplementation Induces Glucose Intolerance Conditional On Sweet Chemoreceptor Sensing
Joan Serrano, Rebecca Hoyd, Daniel Spakowicz, George A. Kyriazis
The Ohio State University, Columbus, OH, United States

Objectives: Epidemiological data suggest that consumption of artificial sweeteners (ASs) is associated with metabolic dysregulation, which may be mediated by gut microbiota. Because ASs are ligands for sweet taste receptors (STRs; T1R2/T1R3), also found in the gut, we tested whether STR-chemosensation is relevant to the metabolic effects of ASs. Methods: Male and female mice (10-12/group) with body deletion of T1R2 (T1R2-KO) and WT littermates (T1R2-WT) were supplemented with drinking water (control) or water plus saccharin (0.1%) for 10 weeks and the effects on glucose metabolism were tested. Results: In individually housed mice, saccharin feeding induced glucose intolerance in T1R2-WT, but not in T1R2-KO mice (p<0.05). Insulin tolerance was not affected by the treatment. However, when mice from the two genotypes were co-housed, the saccharin effect on glucose tolerance disappeared. At baseline, T1R2-KO had elevated fecal short-chain fatty acids compared to T1R2-WT (p<0.001), but no significant difference in community-level fecal microbiota.    Conclusions: Consumption of saccharin may induce glucose intolerance dependent on STR function in mice through dysregulation of, yet unknown, local intestinal mechanisms.

8:50 - 10:50 AMCalusa ABC

Sponsored by PepsiCo

Chair(s): Matt Wachowiak



Olfactory Search Strategy In Freely-Moving Mice

Matt Smear
University of Oregon

Animals strategically sample dynamic environments to optimize their sensory input. For example, when searching for olfactory targets, mice must move and sniff through turbulent odor plumes. To study olfactory search behavior, we have established an operant task in which unrestrained mice report odor source location. Our paradigm affords parametric stimulus control, which has allowed us to determine that mice use odor concentration changes to guide search behavior under these conditions. Using high speed video-tracking and thermal measurement of breathing, we can capture the mouse’s sampling behavior. To reveal structure in this behavior, we have applied machine learning techniques which parse continuous movement trajectories into discrete motifs. Taken together, we have elucidated sensory computation and behavioral structure in an olfactory search task. These findings set the stage for investigation of the neural mechanisms of olfactory search.



Neural Coding For Olfactory Navigation: An Information-Theoretic Viewpoint

Jonathan Victor
Brain and Mind Research Institute, Weill Cornell Medical College

Information theory provides a natural framework for understanding the design principles of sensory systems, particularly regarding how sensory systems take advantage of the statistical properties of the environment, or how they grapple with biological constraints. Here we introduce this framework and apply it to olfactory navigation, with a focus on sampling odor concentration in a turbulent plume.  Two main findings emerge.  First, coarse resolution of odor concentration provides nearly as much information about location as fine resolution.  That is, once a few levels of odor concentration can be distinguished, further information about location can be obtained by obtaining further samples across time or space, but not by increasing resolution for concentration.  Second, optimal coding of odor concentration for navigation is achieved by a disproportionate emphasis on the high end of the odor concentration range, compared to coding strategies that are optimal for plume reconstruction (a strategy known as histogram equalization).  This emphasis is closely approximated by the Hill equation, which describes the nonlinear saturation associated with receptor binding.  Thus, a transformation that universally occurs at the earliest stage of sensory processing may play a crucial role in optimizing  sensory transduction for the purpose of navigation. 


Algorithms And Circuits For Olfactory Navigation In Drosophila

Katherine Nagel
Neuroscience Institute, NYU School of Medicine

Organisms of many species use odor use to navigate towards sources of food in their environment.  This problem is computationally challenging because of the nature of odor signals—odor plumes are turbulent, and have complex spatial and temporal structure.  Thus, navigating towards a food goal requires the nervous system to transform a fluctuating chemical signal into a set of ongoing motor commands.  We have been using the model organism Drosophila to study this process at two levels.  First, we ask at an algorithmic level, how freely behaving flies transform dynamic sensory signals into behavior.  Second, we seek to identify the neural circuits that perform these computations.  In this talk I will present our work thus far on these two topics.  At an algorithmic level, we find that nonlinear temporal processing of odor signals, followed by linear summation of motor components, can account for fly behavior in response to both controlled odor pulses and turbulent plumes.  At a circuit level, we have begun to identify neurons that may transform odor signals into motor commands.  Our work aims to provide insight into the organization of neural circuits that drive a complex goal-directed behavior.


The Navigational Nose: Proposing An Olfactory Function For The Human External Pyramid

Lucia Jacobs
University of California, Berkeley

Homo sapiens is the only great ape species with a prominent external nose. Yet why this structure evolved is not clear. A major selective force in the evolution of olfactory function is its role in spatial navigation; navigation and olfaction are intimately connected at the neural level across the animal kingdom. In vertebrates, this is reflected in the robust and conserved circuitry linking the hippocampus, a navigational center, with the main olfactory system. This relationship between olfaction and navigation may also explain the evolution of the external human nose. I propose that the evolution of efficient bipedality and increased space use in Homo led to a new demand for spatial navigation. Stereo olfaction improves orientation accuracy in diverse animal species; because the human nose increases the physical separation of inputs, it could enhance stereo olfaction. Finally, the variation in nose shape seen in modern humans could reflect a recent response to the Neolithic transition, when the major function of olfactory cognition in sedentary, urban societies could have shifted from navigation to the detection and diagnosis of disease, food spoilage and social signals. 


Observing And Quantifying Odor Valence In The Mouse

Lisa Stowers
Scripps Research

Olfactory sensation drives behavior. A subset of specialized odors including pheromones and kairomones drive stereotyped innate behaviors (such as fear, aggression, and mating) that are relatively easy to observe and quantify.  However, sensation of most traditional odorants does not promote dramatic changes in behavior. Currently, the behavioral significance of common odorants has been largely simplified to tests that infer the inherent level of attraction or aversion (valence). Natural complex food and conspecific odor blends have been shown to elicit attraction while natural predator blends elicit aversion; but the extent to which most monomolecular odors trigger an innate has not been systematically studied. To determine the means to effectively measure innate valence across odor space we have run a direct comparison of behavior in several commonly used odor delivery methods. We find that an individual’s attraction or aversion to an odor varies with the odor delivery arena assay. We suggest that an individual’s approach or avoidance to an odor is not a reliable means of inferring valence and propose either standardizing assay use across the field or identifying more robust methods to measure odor valence in the mouse.

10:00 - 12:00 PMCalusa FGH
CLINICAL SYMPOSIUM: Plasticity in the olfactory system - the clinical perspective

Chair(s): Thomas Hummel and Sanne Boesveldt


Plasticity In Pripheral Olfactory Function

Eric Holbrook
Mass Eye and Ear/Harvard Medical School

The peripheral olfactory system has an inherent plasticity possessing the ability to respond to environmental insults with regeneration of olfactory neurons.  The human condition seems to fall short in this ability compared to lower animals, however evidence exists in animals and humans for the ability to manipulate this regenerative potential.  Examples of conditions in human olfactory disorders will be compared with mouse models to demonstrate the plasticity of the peripheral system. 


Role Of Olfactory Basal Cells In Development Of Anosmia Treatments

Brad Goldstein
University of Miami

The olfactory epithelium in the nose is the peripheral organ for the sense of smell, housing primary olfactory sensory neurons. Olfactory neurons are generally felt to be short-lived, requiring ongoing replacement from basal stem cells to maintain olfactory function. Anosmia (a loss of the sense of smell) in humans can occur in neurodegenerative diseases or due to inflammation, tissue damage or aging. Evidence suggests that neurogenic exhaustion, or excess cumulative damage, may contribute to olfactory loss. Accordingly, our work has focused on understanding mechanisms involved in ongoing adult olfactory tissue maintenance. The lab has used mouse models of olfactory injury and culture systems to study adult olfactory degeneration and regeneration. Findings from these approaches have led to a focus on the role of Polycomb complexes in the epigenetic regulation of olfactory cellular renewal. In addition, we have explored the culture expansion and therapeutic potential of neurogenic olfactory basal progenitor cells.


Neural Plasticity In The Olfactory Bulb And Changes In Parkinsons Disease

Maurice Curtis
The University of Auckland

Olfactory Bulb Changes in Parkinson’s disease


Maurice A Curtis


Department of Anatomy and Medical Imaging, The University of Auckland


Long before a person visits the doctor with the cardinal features of Parkinson’s disease (PD; paucity of movement and rigidity) they will usually have lost their sense of smell. Pathologically, PD is characterised by the accumulation of α-syn in various brain regions and a loss of dopamine cells in the substantia nigra. But, the olfactory bulb is one of the first brain regions affected by the accumulation of α-syn. In the olfactory bulb, existing data suggests that the majority of α-syn accumulates in neurons of the anterior olfactory nucleus. α-syn spreads from the anterior olfactory nucleus to the olfactory tract, anterior olfactory cortex and then into the substantia nigra. We want to understand the early changes in the olfactory bulb that could be key in identifying early targets for slowing or stopping the progression of PD-related brain changes before the cardinal features appear. To this end we have performed studies on ethically sourced normal and PD human olfactory bulbs with a focus on characterising glomerular changes, metal accumulation and cell types affected by α-syn. In this talk I will describe results from: 3D reconstructions of whole human olfactory bulbs that have revealed a ventral glomerular deficit and aberrant placement of many glomeruli in PD; studies of which cell types (neurons, glia, pericytes and microglia) α-syn accumulates in in the bulb; studies that identify metal accumulation in PD olfactory bulbs. In addition, I will discuss earlier research focussed on identifying the extent of plasticity in the olfactory system and the rostral migratory stream in humans. The results of these studies and implications for PD will be discussed.

Decreasing And Increasing Olfactory Function: Central Nervous Changes
Katie Whitcroft


Spontaneous Recovery Of Olfactory Function And Olfactory Training

Antje Welge-Lüssen
University Hospital Basel, ENT Department

Olfactory function in postinfectious or posttraumatic disorders can recover spontaneously. Recovery rate is higher in postinfectious than in posttraumatic disorders and age and duration of the disorder seem to be major prognostic factors. In the last ten years olfactory training has been establised and has been demonstrated to improve spontaneous recovery rate in olfactory disorders. This presentation provides an overview of spontaneous recovery rate in olfactory disorders and different contributing prognostic factors . In addition, olfactory training, its various forms and its effects on the improvement of olfactory function are presented.

10:40 - 11:00 AMCalusa Foyer
Coffee Break

11:00 - 12:40 PMCalusa ABC

Chair(s): Charlotte Mistretta

The Logic Of Taste: Is It Really So Logical?
Stephen Roper
Miller School of Medicine, University of Miami

A number of recent publications attempt to define the “logic” of taste and explain how signals transmitted in gustatory neural circuits are encoded.  Specifically, researchers have focused on understanding how sweet, sour, salty, bitter, and umami tastes are discriminated and whether information for these tastes is transmitted along labeled lines, combinatorial neural pathways, or in some other manner.  Yet even from the earliest recordings of gustatory afferent fibers, hints arose indicating that encoding taste challenges any simple logic.  Single gustatory afferent fibers respond to combinations of sweet, sour, salty, etc. tastes as well as to temperature and touch.  To examine taste signaling in the periphery, my laboratory and that of my colleague, N. Chaudhari, are using confocal Ca2+ imaging of geniculate ganglion neurons in vivo in mice that express GCaMP3 or GCaMP6 in sensory neurons (Kim, Chu et al, Neuron, 2014).  We can record robust signals (∆ GCaMP fluorescence) in geniculate ganglion neurons in response to stimulating the tongue and palate.  Our data suggest that taste qualities are most likely transmitted into the brainstem as some form of combinatorial code, not by unique labeled lines.  Moreover, many individual geniculate ganglion neurons are polymodal, responding to taste as well as temperature and/or touch.  The logic of this gustatory coding escapes us at present but suggests that signal processing is much more complex than previously believed.  Ongoing studies using single cell RNA-seq and transcriptome analyses (Dvoryanchikov, Hernandez et al, Nat Commun 2017) may lead to greater insights.

Anatomical Underpinnings Of Broadly And Narrowly Tuned Taste Neurons
Robin Krimm
University of Louisville School of Medicine

It is unclear whether taste neurons are simply relay cells that carry a labeled-line code from specific subsets of taste receptor cells, or if there is circuitry between receptor cells and nerve fibers that transform neural responses. Nothing is known about the branching characteristics of individual taste neurons or their degree of convergence onto gustatory neurons. If taste neurons simply reflect the response characteristics of taste receptor cell types they innervate, little variation in branching characteristics between individual taste neurons would be required. To determine if this is the case, we traced the peripheral branching patterns of 96 single taste neurons, from where they enter the tongue to their terminations in the taste bud, using sparse cell genetic labeling. These neurons vary tremendously in their branching characteristics, such that individual neurons had anywhere from 1 to 20 separate branches entering between 1-7 taste buds. Cluster analysis was used to separate the neurons into 4 groups each of increasing branch complexity. Based on published EM data, the simplest taste neurons (cluster 1) should innervate approximately 4 taste receptor cells, while the most heavily branched neurons (cluster 4) would be expected to receive information from 16 or more taste receptor cells. We sought to verify this degree of convergence by asking how many labeled taste receptor cells are sufficiently proximal to a single taste neuron such that communication could occur. We found that some fibers only contact one two taste receptor cells of the same type. These neurons would be expected to have responses that directly mimic the taste receptors innervated. Alternatively, other neurons contact as many as 12 different receptor cells of multiple types. Since approximately 1 in 4 taste receptor cells responds to more than one stimulus, neurons innervating many taste receptor cells would be expected to be either broadly tuned or have complex response characteristics due to lateral enhancement and/or inhibition. Current views of gustatory neural coding must consider why some neurons innervate only a few taste receptor cells while others appear to receive heavily convergent information.

Mapping Olfaction Through Transcriptome Profiling
Hiro Matsunami
Duke University

We aim to integrate odorant structures, odorant-receptor interactions and odor representations in the olfactory bulb. Towards this end, our collaborative team took multiple complementary approaches.

First, we conducted a large scale deorphanization of mouse odorant receptors in vitro and in vivo. We developed and optimized methods with which odorant receptor activation was assessed by second generation sequencing, enabling high-throughput matching of odorants and their cognate receptors.

Second, we developed a method to localize rare odorant receptor transcripts present in olfactory neuron axon terminals to olfactory bulb glomeruli. Targeted capture of transcripts from olfactory bulb slices identified enrichment of a set of odorant receptors, defining the glomerular positions on the olfactory bulb surface.

Together with functional imaging of olfactory bulb glomeruli and genetic labeling of axons expressing a specific odorant receptor (see Wachowiak presentation), these approaches allow us to link odorants, odorant receptors, and functional map of olfactory bulb glomeruli.


New Strategies For Understanding Glomerular Odor Maps

Matt Wachowiak
University of Utah

As part of a collaborative effort aimed at understanding how odors are represented in the initial stages of the mammalian olfactory system, our laboratory has focused on how odorant responsiveness maps to glomeruli across the mouse olfactory bulb (OB). Here, we present data from new approaches to this long-studied problem. First, we have used genetic approaches to allow in vivo imaging from all OSNs, combined with a novel high-throughput odor delivery system that allows for rapid and flexible screening of large numbers of odorants at a range of concentrations. Using this approach we have begun mapping OB glomeruli in terms of the odorants to which they exhibit the highest sensitivity, which is typically well below the nanomolar range. This ‘sensitivity map’ of glomeruli confirms a chemotopic organization across the dorsal OB, with domains of glomeruli with high sensitivity to particular odorant classes. Second, in collaboration with the Matsunami lab, we generated two new odorant receptor-tagged mouse lines and have begun extensively characterizing their molecular receptive ranges and temporal dynamics in vivo. Overall, these experiments aim to reveal new insights into how OB glomeruli are organized with respect to olfactory chemical space, the odorant receptor repertoire, and OB circuits.

Building Systematic Representations For Odor Space In Cortex
Bob Datta
Harvard Medical School

The Datta lab studies how information from the outside world is detected, encoded in the brain, and transformed into meaningful behavioral outputs. Here, we describe recent experiments using a combination of chemoinformatics, volumetric population imaging in awake mice and behavioral analysis to explore odor codes in piriform cortex, the main cortical center devoted to olfaction in the mammalian brain. Our findings suggest mechanisms through which inputs from the bulb collaborate with intrinsic circuits within PCx to create systematic representations of the olfactory world, and a means by which the olfactory system can link chemically-related odors to similar behaviors and perceptual qualities both within and across individuals.

12:40 - 1:40 PMPine
Chemical Senses Editorial Board Meeting

1:00 - 3:00 PMCalusa FGH
Industry Symposium: Contribution of Oral and Nasal Chemethesis to Taste, Aroma and Flavor Perception – From Basic Mechanisms to Applications

Chair(s): Beverly Tepper


Industry Symposium: Introduction

Beverly Tepper
Food Science - Rutgers University

Chemesthesis refers to chemically-derived sensations other than taste and smell that include irritation, cooling, tingling and astringency. Astringency is a complex sensation characterized by feelings of dryness, roughness, and tingling/biting on the oral surface. Polyphenol-rich foods such as tea, dark chocolate, wine, and red and purple fruits impart bitterness and astringency that can limit consumer acceptance of these foods even though they deliver important health benefits. Likewise, most flavor and aroma compounds, especially those derived from aromatic herbs and spices, such as cinnamon, clove, and oregano not only impact health, but also exhibit a range of chemesthetic properties that can influence the perceptual experiences of foods, fragrances and other products. Our current knowledge of chemesthesis lags well behind our understanding of other chemosensory systems. This symposium will examine the contributions of chemesthetic sensations to flavor perception and their potential interactions with taste and smell. Five speakers will address this topic from different perspectives including health/nutrition implications, psychophysical assessment and individual differences, underlying biological mechanisms, and finally the challenges/opportunities to developing new products. 


Chemistry, Sensory Attributes, And Health Benefits Of Polyphenols In Nuts And Berries

Bradley Bolling
University of Wisconsin-Madison

Nuts and berries are rich sources of dietary polyphenols. These molecules contribute to the sensation of astringency, but have unique profiles and content specific to each nut or berry. Nut polyphenols are diverse and consist mainly of proanthocyanins, hydrolysable tannins, flavonoids, and phenolic acids. Berries also are rich in proanthocyanidins and anthocyanins and have lesser amounts of hydrolysable tannins, flavonoids, and phenolic acids. The location and profile of polyphenols in the food matrix varies among nuts and berries. Some polyphenols are freely extractable and liberated by mastication from the solid matrix, while others are closely associated with cell wall material and sequestered until transit through the gastrointestinal tract. Furthermore, plant cultivar/variety, growing conditions, degree of ripening, and processing affect polyphenol profile and content in nuts and berries. Upon consumption, polyphenols are metabolized by host tissues and microbiota metabolize. Recent work from our group suggests polyphenols and their metabolites have complex interactions with gut immune cells and microbiota that contribute to its cholesterol-lowering and anti-inflammatory effects. In conclusion, it is necessary to define polyphenol composition, metabolism, and bioactive mechanism to produce high-quality foods that maximize health-promoting efficacy.


Astringency Perception - Salivary Protein Mechanisms And Genetic Variation

Neeta Yousaf
Rutgers University Department of Food Science

Astringency is characterized by sensations of drying, roughening or puckering of the oral surfaces following the consumption of polyphenol-rich foods such as grapes, apples, berries, tea, beer and chocolate. Our current understanding of astringency perception is incomplete, but a widely-held mechanism describes the formation of insoluble polyphenol-protein complexes in the mouth that are thought to erode the lubricity of the salivary pellicle. It is likely that other mechanisms play a role as well.  The perception of astringency varies widely across individuals. Accumulating evidence from our studies and others suggests that genetic variation in the perception and liking of polyphenol-rich foods may be related to differences in the release of specific classes of salivary proteins that are directly involved in the development of the astringency response.

This presentation will review current theories of astringency perception, discuss emerging evidence linking genetic differences in astringency perception (indexed by PROP bitter taste sensitivity) to salivary protein responses and liking of a cranberry beverage.  Understanding the complex interplay between genetics, salivary responses and astringency development may help the industry develop food and beverage products that balance positive health benefits with consumer acceptance.


Olfactory-Trigeminal Interactions: From The Nose To The Brain

Johannes Frasnelli

The trigeminal system is a third chemosensory system, next to smell and taste. Its receptors are located on fibers of Cranial Nerve V, i.e., the trigeminal nerve, within the mucosa of the mouth and the nose. While trigeminal receptors and fibers are independent from the other chemical senses, the trigeminal the olfactory systems are intimately interconnected. Most, if not all odorants stimulate the trigeminal system as well, at least in higher concentrations. Furthermore, trigeminal and olfactory information share central nervous processing areas. As a result, simultaneous presentation of trigeminal and olfactory stimuli leads to complex interactions between both systems. This presentation will focus on different forms of olfactory-trigeminal interactions, on peripheral (mucosal) and central (brain) levels. The comprehension of these mechanisms is necessary to understand the perception of mixed olfactory-trigeminal stimuli.


From Pungency To Pain: Sensing Touch, Taste, And Temperature In The Mouth

Stephen Roper
Miller School of Medicine, University of Miami

Recent findings indicate that the sensory afferent neurons that innervate taste buds, for example geniculate ganglion neurons, respond to many more types of stimuli than the canonical sweet, sour, salty, bitter, and umami compounds.  Specifically, so-called somatosensory stimuli such as touch, texture, and temperature also excite “gustatory” geniculate ganglion neurons.  These findings give rise to the suggestion that the end organs in taste—taste buds—really are multisensory structures.  The puzzle then becomes, how do “gustatory” afferent neurons encode and transmit signals that differentiate these multi-faceted orosensory perceptions (taste, touch, texture, temperature)?  Moreover, higher brain centers along the taste axis, such as the parabrachial nucleus, integrate signals from the trigeminal ganglion (classically believed to transmit somatosensory information) with “gustatory” afferent signals from other sensory ganglia. This further contributes to the complexity of orosensory coding.  I will explore these and related concepts in my presentation.


Taste'S Great And Good For You - Challenges To Developing Healthy Products For Today'S Consumers

Kyle Shadix

The challenges and headwinds the CPG industry faces today.  Learn about Generation-Z, and how the economy, politics, culture, & technology have shaped them.  How today's challenges and headwinds will influence new product development for future generations. What technical unlocks from the scientific community will help solve some of the mega-issues and challenges facing tomorrow's consumers. 

1:40 - 3:20 PMCalusa ABC

Chair(s): Diego Restrepo


The Role Of The Olfactory Bulb In Human Odor Perception

Johan Lundstrom
Monell Chemical Senses Center

In non-human animal models, the olfactory bulb (OB) has been demonstrated to be a key processing area for the olfactory percept. In human odor perception, however, the role of the OB is poorly understood. This lack of knowledge originates mainly from the absence of any non-invasive method to acquire functional data from the human OB. In this talk, I will outline our attempts to map the role of the human OB in odor perception. I will first outline a new method that enables the measurement of functional processing within the human OB on a millisecond time-scale. I will then present data suggesting that the human olfactory bulb is processing both intensity and pleasantness, but at different time intervals, indicating the relevance of the temporal separation of perceptual processes.


Coordinates For Representing Natural Odors

Tanya Sharpee
Salk Institute

biochemical reactions create many by-products. Thus, the presence of certain bacteria in the food becomes associated with the emission of certain volatile compounds. This perspective suggests that it would be convenient for the nervous system encode odors based on statistics of their co-occurrence within natural mixtures rather than based on the chemical structure per se. I will discuss how this statistical perspective makes it possible to map odors to points in a hyperbolic space. Hyperbolic coordinates have a long but often underappreciated history of relevance to biology. For example, these coordinates approximate distance between species computed along dendograms, and more generally between points within hierarchical tree-like networks. We find that these coordinates, which were generated purely based on the statistics of odors in the natural environment, provide a contiguous map of human odor pleasantness. Further, a separate analysis of human perceptual descriptions of smells indicates that these also generate a three dimensional hyperbolic representation of odors. This match in geometries between natural odor statistics and human perception can help to minimize distortions that would otherwise arise when mapping odors to perception. We identify three axes in the perceptual space that are aligned with odor pleasantness, its molecular boiling point and acidity. Because the perceptual space is curved, one can predict odor pleasantness by knowing the coordinates along the molecular boiling point and acidity axes.


A Structured Representation Of Odors In The Fly Mushroom Body

Elizabeth Hong
California Institute of Technology

Odors are represented in the mushroom body by neurons that are believed to pool input from random subsets of olfactory receptors. Using methods we have developed for reliably imaging near-complete mushroom body representations at cellular resolution, we show that the structure of mushroom body representational space is similar across individual flies for a test set of fifteen diverse odors. Preliminary results are consistent with the preservation of some, but not the majority of, pairwise odor relationships from peripheral coding space to mushroom body coding space. These results are compared to predictions made by simple connectivity models of KC responses that assume random or weighted pooling of glomerular inputs. 


Sensory Representation In The Drosophila Brain

Sophie Caron
University of Utah

Uncovering fundamental mechanisms of neuronal connectivity that enable associative brain centers to learn efficiently is an important goal of neuroscience. In the Drosophila melanogaster mushroom body, the constituent Kenyon cells receive input from olfactory projection neurons. Each projection neuron connects to one of the fifty glomeruli in the antennal lobe, the primary olfactory processing center. We and others have shown that these connections are random in that there are no sets of glomeruli converging preferentially onto a given Kenyon cell. However, we found that the glomeruli are not represented with equal frequency among Kenyon cell inputs. Certain glomeruli form many more connections than expected under a uniform distribution, whereas other glomeruli form far fewer connections than expected. We are testing the idea that this non-uniform distribution, which we termed ‘biased randomness’, serves an important biological function, namely to predispose the learning ability of the mushroom body towards certain ethologically pertinent stimuli. To test this idea, we built two mathematical models of the mushroom body: one model was built using the biased distribution of input that we measured experimentally, while the other model uses a uniform distribution of input. Both models generate very similar representations for most of the tested odors. However, we found that each model generates strikingly different representations for a few ethologically relevant odors. Odors activating overrepresented glomeruli activate many more Kenyon cells than odors activating underrepresented glomeruli do. Consequently, although both models show overall similar learning performance, they perform differently in tasks involving these ethologically relevant odors. We are proposing that overrepresentation serves a biological function, namely to enable odors that must be learned in many different contexts, pheromones, for instance, to be represented by a large number of Kenyon cells. In contrast, underrepresentation might be used as a strategy to prevent the mushroom body from representing — and possibly learning — odors with strong innate valence. We are currently testing this idea further by measuring the biases in connectivity in the mushroom body of other Drosophila species, namely Drosophila sechellia, that have evolved in different ecological niches and therefore have different olfactory preferences. Our preliminary data suggest that biases shift in a predictable manner, reflecting the expected olfactory ecology of a species. Altogether, our work supports the idea that ‘biased randomness’ is a wiring mechanism that predisposes associative brain centers to learn efficiently.


The Neural Code For Food In The Nucleus Of The Solitary Tract

Pat Di Lorenzo
Binghamton University

Recent work has shown that taste responses in the nucleus of the solitary tract (NTS), a structure conventionally called a “taste relay,” may be modulated by olfactory stimuli, suggesting that cells in the NTS may be optimally tuned to complex stimuli, i.e. food. In addition, our work has shown that the NTS also contains an abundance of cells that track consummatory behavior, presumably through somatosensory feedback from the periphery. In an effort to determine how the NTS encodes natural stimuli, we have studied the responses of NTS cells as the animal eats solid foods. Rats were implanted with drivable microelectrode bundles positioned in the NTS and allowed to recover. Thereafter, rats were tested daily with traditional tastants (sucrose, NaCl, citric acid, quinine and MSG) presented through a lick spout. Immediately after the “lick” session, rats were presented with three “wells” filled with various foods (chocolate, salted peanuts, sour apples, broccoli) along with one empty well. Food wells were located at the four corners of the experimental chamber. An infrared beam across the entrance to each well recorded well entry and exit. Food sessions were videotaped and scored offline for eating beginning and end. Results showed that rats explore the contents of the well with their tongues, producing excitatory responses in NTS cells. These excitatory well responses often began before the rat entered the well, suggesting a top-down drive. The onset of eating is most often accompanied by an attenuation of firing rate; however, analyses pf temporal coding suggests that the responses to eating, though small, are nevertheless informative. In all, results point to the idea that the function of the NTS is to evaluate food in its multifaceted sensory and sensorimotor totality.

3:20 - 3:40 PMCalusa Foyer
Coffee Break

3:30 - 5:00 PMGreat Egret
NSF and NIH Programs relevant to the Chemical Sense

NIH officers present information for PIs in the chemical senses on new initiatives at NIH. Dr. Christopher Lynch invites PIs to learn about the trans-NIH Nutrition Research Task Force that spans across 17 NIH Institutes, Centers and Offices. Priority areas include integrative physiology, ingestive behavior and sensory nutrition. Dr. Lynch is Chief of the Nutrition Research Branch at NIDDK and leads the trans-NIH Nutrition Research Task Force (NRTF). Dr. Coryse Hillaire-Clarke invites Pis to learn about the mission of the National Inst. on Aging, highlighting new funding announcements emphasizing normal aging, Alzheimer?s Disease and Related Dementias. Chemosensory researchers looking to add research in these areas to their chemosensory research will find this talk informative. Dr. Edda Dr. Thiels will describe NSF neuroscience programs relevant to AChemS PIs.

3:40 - 5:00 PMCalusa ABC

Chair(s): Pat Dilorenzo


Synaptic Integration Of Bla And Vpmpc Inputs In The Gustatory Cortex

Arianna Maffei
Stony Brook University

The gustatory cortex is a central component of the taste system, and is hypothesized to integrate both chemosensory and affective dimensions of taste stimuli. However, to date, the neuronal and circuit mechanisms involved in this process remain unclear. In this talk, I will present our recent results aimed at determining the synaptic mechanisms for the integration of thalamocortical and amygdalocortical inputs to the primary gustatory cortex. The thalamocortical projection from the taste thalamus provides the gateway for chemosensory information to the gustatory cortex, while the basolateral nucleus of the amygdala has been identified as a major contributor of hedonic information regarding taste stimuli. We have identified the postsynaptic targets and synaptic properties of both thalamocortical and amygdalocortical inputs to the gustatory cortex. In addition, anatomical tracing and electrophysiological recordings in vivo have allowed us to identify a group of neurons receiving direct monosynaptic input from thalamus and amygdala, thus potentially acting as direct integrators of chemosensory and hedonic information. In this group of neurons, amygdalocortical inputs modulate the amplitude of thalamocortical responses with dynamics that depend on the recruitment of inhibitory circuits. Our results indicate that a group of neurons in the gustatory cortex can integrate chemosensory and hedonic information, and that the recruitment of GABAergic inhibitory circuits regulates the synaptic dynamics of integration of these components.

The implications of our results extend beyond the understanding of taste perception. As taste in human and rodents is characterized by sensory and affective dimensions, it is a unique model for understanding common mechanism of sensory processing, as well as for investigating how information about the affective dimensions of a sensory stimulus may modulate perception. Thus, this work may offer new insight into neural circuit dysfunction in disorders associated with altered sensory perception, or anhedonia.


Taste Quality Representations In Human Eeg Predict Taste-Related Behavior

Kathrin Ohla
Research Center Jülich

The taste system provides important information about the edibility and makro-nutrient content of a food via differentiation between taste qualities. Specific receptors on the tongue are activated by chemicals signifying a taste quality before the signal is conveyed to the brain. How this peripheral signal is used by the central nervous system to encode taste quality is largely unknown. Cortical activation patterns change rapidly, within milliseconds, rendering temporal information a candidate variable for taste quality coding. Using non-invasive electrophysiological recordings, which provide a window into taste-neuronal processing with millisecond resolution, I will illustrate that large-scale neuronal response patterns carry information about taste quality and bear significance to taste-related behavior. I will demonstrate that these neuronal response patterns carry information about which taste participants tasted and that their onset predicts the timing of perceptual decisions. Furthermore, I will present novel data that suggest that taste perception and neuronal responses are susceptible to information. Together, I aim to show that the information encoded in taste-related neural response patterns is also the foundation for gustatory decision-making and that the timing aligns with task-specific goals.


Sucrose Intensity Coding And Decision-Making In Rat Gustatory Cortices

Ranier Gutierrez

Sucrose’s sweet intensity is one attribute contributing to the overconsumption of high-energy palatable foods. However, it is not known how sucrose intensity is encoded and used to make perceptual decisions by neurons in taste-sensitive cortices. We trained rats in a sucrose intensity discrimination task and found that sucrose evoked a widespread response in neurons recorded in posterior-Insula (pIC), anterior-Insula (aIC), and Orbitofrontal cortex (OFC). Remarkably, only a few Intensity-selective neurons conveyed the most information about sucrose’s intensity, indicating that for sweetness the gustatory system uses a compact and distributed code. Sucrose intensity was encoded in both firing-rates and spike-timing. The pIC, aIC, and OFC neurons tracked movement direction, with OFC neurons yielding the most robust response. aIC and OFC neurons encoded the subject’s choices, whereas all three regions tracked reward omission. Overall, these multimodal areas provide a neural representation of perceived sucrose intensity, and of task-related information underlying perceptual decision-making.


The Role Of Taste Activity In Shaping The Morphology Of Central Gustatory Circuits.

David Hill
University of Virginia

Central coding of sensory information reflects the morphological characteristics of ascending and descending circuits. Changes in the size and distribution of sensory inputs (e.g., presynaptic terminals) and the dendritic architecture of recipient sensory neurons, will impact the amount and type of neural information coded by single neurons. We and others have used the developing gustatory system to examine how inputs into the first synaptic relay in the brain – the nucleus of the solitary tract (NST) – change with age during normal development and how the normal developmental program can be manipulated through alterations of taste-elicited neural activity. Findings will be presented where sodium-salt activity was manipulated during development in rodents and its consequences on the terminal field organization of gustatory nerves as they make their inputs into the NST and its consequences on the dendritic architecture of NST neurons that receive and code these inputs. We will also speculate on how age- and experience-related alterations in taste bud function and central nervous system events shape these circuits that drive coding of taste quality and quantity.


Supported by NIH grant DC000407.

5:30 - 6:30 PMMangroves Patio
Travel Fellowships for Diversity Award Recipients Dinner

7:00 - 9:00 PMCalusa ABCD
Polak Award Presentations

Chair(s): Jay Gottfried

Taste Of Time &Ndash; A Porous Medium Model For Human Tongue Surface To Investigate Temporal Profile Of Gustatory Perception
Zhenxing Wu, Kai Zhao
The Ohio State University, Columbus, OH, United States

“A flash of light” or “a sound of twig snap” – sensory systems are remarkable in their temporal resolutions. Yet for taste, its temporal response is complicated by the transport and diffusion processes for the stimuli to reach the taste receptors - through the papillae, taste pore, etc., which we still lack a clear understanding of. The aim of this work is thus to computationally investigate the taste stimulus transport by modeling the surface of human tongue as a porous medium. Based on scan electron microscopies of human tongue in literature, the porosity and permeability of the papillae structure were determined by volume estimation and Kozeny-Carman equation, adapted for porous fiber structure, to be 80% and 1.4e-8 m2, respectively. The model then replicated the historical experiments conducted by Kelling and Halpern in 1986. We simulated a turbulent pipe flow with an elliptical opening placed across the top surface of a human tongue, with delivery of 100 to 1000 ms pulses of 500 mM sodium chloride or 2 mM sodium saccharin. We found that the concentration profile within the papillae structure for both stimuli rises with significant delay, only reaches 52% of the delivered concentration in the first 100ms and to 99% only at pulse duration greater than 400 ms. Surprisingly, the predicted concentration-time profile matches extremely well with the experimental taste perception and intensity rating (r=0.65), e.g. subjects rated 100 ms pulse as only 55% strong as a 2s pulse of NaCl, but 90% for 1s pulse. Our study demonstrated the validity and novelty to model human’s tongue as a porous material to significantly simplify the analytical and computational approaches, and confirmed that the peripheral transport processes may have significant impact in human gustatory perceptions.

Comparison Of Odorant Intensity-Response Functions Of Olfactory Bulb Inputs, Outputs, And Interneurons Using In Vivo Two-Photon Imaging.
Shaina M. Short, Matt Wachowiak
University of Utah, Salt Lake City, UT, United States

Changes in intensity-response functions are a basic building block of input-output transformations by any network. In vertebrates, the first transformation of olfactory information is mediated by circuits of the olfactory bulb (OB). We used in vivo imaging to investigate how glomerular circuits shape mitral and tufted cell (M/TC) intensity-response functions in the mouse OB. We selectively expressed calcium reporters in olfactory sensory neuron (OSN) inputs, periglomerular (PG) and short axon (SA) inhibitory interneurons, and M/TCs to compare odorant-evoked intensity-response functions of these neuron populations using repeatable, artificial inhalation in anesthetized mice. We analyzed how odorant concentration impacted the magnitude, polarity and inhalation-linked temporal dynamics of responses in each cell type. We also used dual-color, dual-indicator imaging to simultaneously measure responses among two cell types within the same glomerulus. Comparing OSN and M/TC responses, we found that M/TC intensity-response functions had a compressed dynamic range relative to OSN inputs and could show nonmonotonic intensity relationships, including the emergence of suppressive response components and complex changes in inhalation-linked response dynamics. PG and SA cell intensity-response functions were more similar to those of OSN inputs. Notably, dual-color imaging of PG cells and M/TCs did not reveal M/TC suppression coincident with activation of PG cells at near-threshold intensities, a result that is inconsistent with a popular model of intensity-dependent feedforward inhibition of M/TCs. Instead, PG and SA cells may impact the gain and alter the temporal dynamics of M/TC responses, hypotheses which can be tested using cell-type specific inactivation of these interneurons.  

Diet And Dietary Context Influence Expression Of Salivary Proteins That May Modulate Oral Sensation
Cordelia Running, Ciera Crawford
Purdue University, West Lafayette, IN, United States

Salivary proteins bind and alter flavor stimuli. Yet, only a few of these proteins have been extensively studied for contributions to individual oral sensory variability. Even less established is how expression of these flavor-modulating salivary proteins is regulated. Many salivary proteins also have functional analogs in foods. For example, milk caseins mimic the function of salivary proline rich proteins (PRP) in binding astringent and bitter polyphenols. We designed this experiment to test whether exposure to polyphenol-containing chocolate would alter expression of salivary proteins, particularly those thought to influence bitterness or astringency. By using both cow’s milk and almond milk, we also tested whether the presence of cow’s milk caseins might block any effect of chocolate exposure on salivary proteins. Results indicate two PRP increased in abundance after one week of drinking 24 fl oz of chocolate milk per day (N=50), with one PRP increasing for both milks (PRP27, p=0.036 and 0.047) and the other only for almond milk (PRP4, p=0.032). Several salivary cystatins, which may correlate with bitterness acceptance, also increased in response to the chocolate intervention for both milk types (all p≤0.043). Notably, many other salivary proteins also changed in response to chocolate milk consumption, including a variety of proteins potentially related to immune responses. These results indicate that diet changes salivary protein composition, and those changes may relate to oral sensory experiences as well as immune function. This work may aid in developing interventions designed to alter saliva in ways that improve the flavor of certain pharmaceuticals or healthy foods, which are often bitter or astringent.  

Targeted Stimulation Of Human Orbitofrontal Networks Disrupts Odor Reward-Guided Behavior
James D. Howard1, Rachel Reynolds1, Devyn E. Smith1, Joel L. Voss1,2,3, Geoffrey Schoenbaum4, Thorsten Kahnt1,3,5
1Department of Neurology, Northwestern University, Chicago, IL, United States, 2Department of Medical Social Sciences, Northwestern University, Chicago, IL, United States, 3Department of Psychiatry and Behavioral Sciences, Northwestern University, Chicago, IL, United States, 4National Institutes on Drug Abuse, Intramural Research Program, Baltimore, MD, United States, 5Department of Psychology, Northwestern University, Evanston, IL, United States

Outcome-guided decision making requires knowledge of the current value of expected rewards. The ability to infer values “on-the-fly” has been classically examined using the reinforcer devaluation paradigm, in which responses to a conditioned stimulus (CS) are probed before and after selective devaluation of a typically chemosensory unconditioned stimulus (US) predicted by the CS. Animal studies show that lesions to, or inactivation of, the orbitofrontal cortex (OFC) results in continued responding to the CS predicting a devalued US, demonstrating this region’s necessity for outcome-guided behavior. While human neuroimaging studies have established a correlational link between OFC activity and updated reward expectations in devaluation tasks, whether this region plays a causal role in human outcome-guided behavior has not been determined. Here we used transcranial magnetic stimulation (TMS) to non-invasively and temporarily disrupt human OFC networks prior to satiety-induced sensory-specific devaluation of food odor rewards. Compared to subjects who received sham stimulation, those in the TMS group failed to exhibit a devaluation effect, such that they continued to choose Pavlovian cues predicting devalued odor rewards. Importantly, TMS did not impair the ability to make value-based choices, suggesting that OFC is critical for inference of updated reward values, but not economic choice in general. These findings point toward a causal role for OFC in human outcome-guided control of behavior, and demonstrate the feasibility of targeting OFC with TMS. Given the integral role that OFC plays in olfactory processing, this represents a promising technique for studying its precise contribution to odor sensation and perception.

Genetic Depletion Of Class I Odorant Receptors Impairs Behavioral Responses To Organic Acids
Annika Cichy1, Ami Shah1, Adam Dewan1, Rodrigo Pacifico2, Sarah Kaye1, Thomas Bozza1
1Department of Neurobiology, Northwestern University, Evanston, IL, United States, 2Present address: Firmenich, New York, NY, United States

The mammalian main olfactory pathway detects volatile chemicals via two different classes of canonical odorant receptors (ORs), the class I and class II ORs. Class I OR genes are evolutionary conserved in vertebrates and account for ~ 10% of the mouse OR gene repertoire. Yet, the functional contribution of class I ORs to olfaction is not known. The class I OR genes are found in an extensive cluster, interspersed among other genes, making it difficult to study the function of these ORs by deleting the entire cluster. Here, we report that deletion of a single cis-acting enhancer element - element 1 (E1) - leads to the functional loss of a significant number of class I ORs. RNA sequencing revealed that mRNA expression levels were significantly downregulated for 69 out of 132 intact class I OR genes, with expression completely abolished for 8 of these genes. Surprisingly, the number of class I glomeruli was reduced by ~50% indicating that moderate loss of OR expression can result in glomerular loss. Consistent with this, the number of glomeruli responding to short chain organic acids was significantly reduced in deletion E1 mice, and these mice exhibited loss of behavioral aversion to 2-methylbutyric acid and 5-methylhexanoic acid.  Together, our findings demonstrate that removal of an OR gene regulatory element can have significant impacts on odor perception, and indicate that class I ORs play a critical role in representing specific volatile organic acids.

Two Parallel Pathways For Olfactory Processing In The Mammalian Brain
Honggoo Chae, Arkarup Banerjee, Dinu F. Albeanu
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, United States

Understanding the interplay between feedforward and feedback signals across interconnected brain areas is essential for unveiling the computations they perform. Across the brain, specialized long-range circuits support different streams of processing and broadcast multiple features of sensory stimuli and diverse substrates for planning and execution of motor actions. To date, the logic of information flow within the early mammalian olfactory system remains poorly understood. It is not known whether different projection neurons carry different signals to particular areas, and to what degree feedback from different target brain areas to the sensory periphery is specific to their input channels. Here we find that activity of the two classes of olfactory bulb outputs, the mitral and tufted cells (MCs and TCs) which innervate distinct sets of higher brain areas, including the piriform cortex (PC) versus the anterior olfactory nucleus (AON), is in turn regulated by differential feedback from these areas via multiphoton calcium imaging in awake head-fixed mice. Overall, feedback signals from PC and AON complemented each other in controlling the response amplitude, timing and pairwise correlation of odor representations at the level of mitral versus tufted ensembles, in a stimulus and cell specific manner. Furthermore, odor specific, robust sensory representations emerge already in the bulb outputs. TCs ensemble substantially outperformed MCs in decoding concentration invariant stimulus identity, while operating in largely a feedforward fashion. In contrast, the odor decoding performance of MCs was further drastically impaired by removal of PC feedback. These results identify two parallel feedforward-feedback loops in the early olfactory system, and indicate they have specialized roles in odor processing.

9:00 - 11:00 PMEstero Ballroom
Poster Session II

Olfaction Dominates Visual Perception: Behavioral And Cortical Effects
Jonas Olofsson1, Thomas Hörberg1, Ingrid Ekström2, Camilla Sandöy1, Maria Larsson1
1Stockholm University, Stockholm, *, Sweden, 2Karolinska Institute, Stockholm, *, Sweden

During multisensory experiences, visual stimuli typically override non-visual stimuli. Such ”visual dominance” effects might stem from inhibition across sensory systems. Does visual dominance generalize to odor-visual pairings? We developed a binary categorization task (fruits vs flowers) with congruent and incongruent odor-picture pairings and a delayed auditory target probe that informed about categorization modality (olfactory vs visual). We investigated behavioral and cortical (ERP) responses.For congruent pairings, we found better accuracy for visual decisions. However, for incongruent pairings, we instead observed faster RTs for olfactory decisions. Incongruent olfactory stimuli thus interfere more with visual decisions than vice versa.Our ERP results from auditory targets on incongruent trials gave supporting evidence for olfactory dominance over visual perception; higher P300 amplitudes were more strongly correlated with faster RTs during visual categorization. A late “slow wave” ERP effect had later onset and longer latency during visual vs olfactory decisions. This indicates that in order to rapidly and successfully categorize visual stimuli (and ignore incongruent odors), participants need to allocate additional attentional and working memory resources. In sum, both behavioral and ERP effects suggest a higher level of interference from incongruent olfactory, compared to visual, input.These findings suggest that asymmetric inhibition across sensory systems is a fruitful way of studying perceptual dominance, and that olfactory stimuli can dominate visual perception, refuting the general notion of ”visual dominance”.

Inia: Scripts For Exploring Localized Genomic Regions In The 1000 Genomes Project
Vicente A Ramirez1,2, Michael Wallace1, Stephen Wooding1,2
1University of California Merced, Merced, CA, United States, 2UC Merced Health Sciences Research Institute, Merced, CA, United States

Public genome sequence repositories contain extensive data from genes encoding chemosensory pathways. These data are highly valuable in efforts to dissect chemosensation’s molecular basis. However, they are difficult to extract and analyze due to the large size of repositories and number of genes involved. To simplify and enhance access, we developed the Inia software package. Inia facilitates the investigation of localized genomic regions by providing tools to extract, organize, and summarize variants in the 1000 Genomes Project catalogue, one of the largest whole-genome sequence database currently available. Given an input file specifying genes and regions to be analyzed, Inia automatically extracts and integrates 1000 Genomes data with information on functional effects catalogued in the Ensembl database and computes population genetic statistics including allele frequencies, heterozygosity, genetic distance between populations (Fst), and Hardy-Weinberg equilibrium. Inia‘s output provides further summary information consisting of site by site annotations of genomic features such as exon number, codon and amino acid changes, functional effects predicted by SIFT and PolyPhen2 scores, catalogued clinical relevance of the coding variants via ClinVar, and occurrences of the variant in the literature via PubMed. Thus, Inia provides a rapid yet comprehensive overview of variation in any genomic region. Here, we illustrate the use of Inia to in an analysis of five representative chemosensation genes, TRPV1TRPM8GNAT3TAS1R1 and TAS2R16 with an example input file, run commands, and output.

Chemesthesis And Trp Channels In The Wolf Spider, Tigrosa Georgicola.
Cecil J. Saunders, Hayden M. Graser, Nandan J. Patel, Glen S. Marrs, Erik C. Johnson
Wake Forest University, Department of Biology, Winston-Salem, NC, United States

Spiders primarily prey on other arthropods—including each other—and many arthropods produce chemical defenses to avoid predation. Many of these chemical defenses guard against vertebrate predation by modulating Transient Receptor Potential (TRP) channels. Thus, it seems probable that these chemical defenses may act to deter predation via activation of spider TRP channels as well. However, little is known regarding the identity or function of spider TRP channel homologs. In the present study, we present both behavioral assays and molecular data establishing the TRP-relevant chemesthestic repertoire of the wolf spider Tigrosa georgicola. Spiders reject prey crickets coated with allyl isothiocyanate (AITC) and menthol but consumed crickets treated with capsaicin normally. Additionally, we applied canonical chemesthetic compounds (AITC, methanol, capsaicin) to individual spider limbs. Stereotypical grooming behavior was immediately apparent after exposure to AITC and persisted for some time, in contrast to vehicle applications that showed no responsiveness. To determine the identity of TRP channel homologs, we extracted and sequenced RNA from the brains of T. georgicola (n=3). A de nova assembly of this neural transcriptome was then preformed with Trinity and annotated with Trinotate. Transcripts predicted to code for protein homologs of TRPA1, TRPC4, TRPC5, TRPM1, TRPM2 and TRPV4 were identified in the T. georgicola transcriptome and confirmed via RT-PCR. 

Taste Cell Turnover Regulates Taste Nerve Fiber Complexity
Zachary D. Whiddon, Robin F. Krimm
Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY, United States

The continual replacement of taste cells creates interesting questions regarding how the innervating neurons are impacted. Here we ask how the morphology of neuron endings within taste buds is affected when taste cell entry is inhibited and reestablished. Inhibition of sonic hedgehog signaling (Shh) is thought to inhibit taste cell turnover. Consistently, fewer new cells were added to individual taste buds after 10 days (0.591±0.282 (p<0.009, df=5)) and 16 days (1.10±0.802 (p<0.011, df=4)) of Shh inhibitor treatment compared to vehicle treatment (2.64 (±0.643)). Taste bud volume did not decrease significantly after 10 days (p=0.242, df=4), but had decreased by 16 days of treatment (p<0.011, df=4). We next examined how taste nerve fiber extension into the gustatory epithelium is affected by preventing taste cell turnover. In normal taste buds, fibers are most numerous at the base of the bud (in the nerve plexus) with an average of 19.1 (±2.16) fibers present. Number of fibers within this nerve plexus are decreased after 16 and 23 (p=0.008, df=4), but not 10 days of Shh inhibitor (p=0.136). However, 10 days of Shh inhibitor does cause a loss of fibers at higher levels within the taste bud (p=0.036 at 6 µm above the plexus). A finding consistent with loss of higher order branches before elimination of fibers within the nerve plexus at the taste bud base - this a model that we are currently testing. A recovery period of 7 days following 16 days of inhibition restores taste cell entry (5.63 (±1.06)), but does not restore fibers within the plexus. This suggests that recovery of normal branch morphology requires more than 7 days of cell turnover. These results provide evidence for the hypothesis that normal branch morphology within the taste bud is supported by taste cell turnover.

Functional Properties And Synaptic Connections Of Dopamine D3 Receptor-Expressing Neurons In The Ventral Striatum
Yun-Feng Zhang1, Janardhan P Bhattarai1, Julia Mohrhardt2, David Fleck2, Wenqin Luo1, Johannes Stegmaier3, Marc Spehr2, Minghong Ma1
1Department of Neuroscience, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, United States, 2Department of Chemosensation, Institute for Biology, RWTH Aachen University, Aachen, *, Germany, 3Institute of Imaging and Computer Vision, RWTH Aachen University, Aachen, *, Germany

The Islands of Calleja (IC) are dense cell clusters located in the ventral striatum, predominantly in the olfactory tubercle (OT). Unlike the ventral striatum which mainly contains medium spiny neurons (MSNs) expressing dopamine D1 or D2 receptor, the IC contain tightly packed, GABAergic granule cells expressing D3 receptor and additional D3 neurons are also scattered outside the IC in the ventral striatum. By crossing transgenic D3-Cre mice with Cre-dependent reporter lines, we obtained D3-tdTomato and D3-ChR2 (channelrhodopsin-2) mice to study functional properties and synaptic organization of D3 neurons. Whole-cell patch clamp recordings revealed that both D3 neurons inside and outside of IC can be classified into two subtypes. Upon current injections, ~70% (39 out of 55, inside IC) and ~83% (24 out of 29, outside IC) of the cells fired multiple spikes while the remaining fired only a single spike. Voltage-clamp analysis revealed that only the multiple spiking neurons exhibited predominant transient potassium current (IA)—fast inactivation of IA may allow these neurons to fire repeatedly. We next examined local synaptic connections of the IC D3 neurons. Upon blue light activation of the IC D3-ChR2 neurons, inhibitory postsynaptic currents were evoked in 61.1% (22 out of 36) of the OT MSNs and in 33.3% (13 out of 39) of IC D3-ChR2 negative neurons. Conversely, nearly half of the IC D3 neurons (13 out of 29) received monosynaptic inhibition from the OT D1 MSNs. Furthermore, whole-brain CLARITY imaging of D3-tdTomato mice revealed that these “islands” form a continuous, interconnected network. We are currently mapping whole-brain inputs and outputs of IC D3 neurons and investigating their functional significance via optogenetic manipulations and mouse behaviors.

Sex Differences In Taste Anatomy And Psychophysics: An Update
Linda M. Bartoshuk1, Valerie B. Duffy2, Howard J. Hoffman3, Derek J. Snyder1, Jennifer J. Stamps4
1University of Florida Center for Smell & Taste, Gainessville, FL, United States, 2University of Connecticut, Storrs, CT, United States, 3NIDCD, Bethesda, MD, United States, 4Trait Bioscience, Los Alamos, NM, United States

Twenty five years ago, we published a paper on sex differences including fungiform papillae (FP) counts and psychophysical assessments of the ability to taste PTC/PROP (phenythiocarbamide/6-n-propylthiouracil). Earlier papers had hinted that females had lower thresholds for PTC than did males, but did not confirm this with statistical analyses. We revisited those early studies and did the analyses to confirm that females had statistically significantly lower PTC thresholds. We also confirmed this using PROP, a chemical relative of PTC that is safer to test. In addition, we demonstrated that females (N=25) had more fungiform papillae than did males (N=23) (Bartoshuk, Duffy & Miller, 1994). Now we have accumulated a much larger database and we provide an update. FP were counted in circular templates (6 mm diameter) placed on either side of the tip of the tongue (the circles touched the midline and the edges of the tongue). The distribution for the counts in females (N=464) was displaced toward higher values than those for males (N=268).  Dividing counts by the median for all subjects (26), chi square analysis showed that females had significantly more FP counts above the median than did males (Chi square = 13.5, p = 0.0002).  We have improved psychophysical comparisons of perceived intensity. Using magnitude matching (Bartoshuk et al, 2004) on a subset of the subjects for whom we have FP counts, we compared the perceived bitterness of PROP papers (pieces of filter paper impregnated with 1.6 mg PROP) in females (N=298) and males (N=158). Chi square analysis of the distributions of the perceived bitterness showed that the distributions were significantly different; the females showed fewer low PROP ratings (nontasters) and more high PROP ratings (supertasters). The earlier observations were confirmed.

Lipopolysaccharide-Induced Inflammatory Cytokine Expression In Taste Organoids
Shan Feng1,2, Leyitha Achoute1,3, Robert F. Margolskee1, Peihua Jiang1, Hong Wang1
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2Southwest University, Chongqing, *, China, 3Lincoln University, Lincoln University, PA, United States

Inflammatory cytokines are important regulators of metabolism and food intake. Expression of certain cytokines can be markedly induced in subsets of taste receptor cells under acute and chronic inflammatory conditions. This may contribute to the altered taste perception and preference associated with many diseases. Although the molecular mechanisms of cytokine induction are well characterized in immune cells, they remain poorly understood in taste bud cells, in part due to the difficulties of performing biochemical analyses with a limited number of taste cells. The recently developed taste organoid model provides an opportunity to carry out these mechanistic studies in vitro. However, it was unknown whether taste organoids respond to inflammatory stimuli as do in vivo native taste cells. Here we analyzed inflammatory cytokine induction in taste organoids and in mouse taste tissues. We treated organoids and mice with lipopolysaccharide (LPS), a bacterial cell wall component that induces robust inflammatory responses. Our results show that, similarly to native mouse taste cells, taste organoids responded strongly to LPS by quickly upregulating expression of many genes, including tumor necrosis factor (TNF) and interleukin-6 (IL-6). The levels of TNF mRNA and protein in taste organoid cultures remained elevated even 72 h after adding LPS. The dynamics of TNF and IL-6 induction in taste organoids closely resembled that in endogenous taste epithelium but was different from that in Raw264.7 monocyte/macrophage cells. These results indicate that the induction of inflammatory cytokines in taste cells may utilize some unique mechanisms differing from those in immune cells. Our results also suggest that taste organoid cultures provide a useful tool to dissect these mechanisms.

Kokumi Taste Perception Of The Domestic Cat (Felis Catus).
Anni Laffitte1, Matthew Gibbs1, Carlos Hernangomez de Alvaro1, Marcel Winnig2,3, Timo Vennegeerts2,3, Boris Klebansky4, Richard Fine4, Scott McGrane1
1Mars Petcare, WALTHAM Centre for Pet Nutrition, Melton Mowbray, *, United Kingdom, 2Axxam SpA, Milan, *, United Kingdom, 3IMAX Discovery GmbH, Dortmund, *, Germany, 4BioPredict, Inc., Demarest, NJ, United States

Kokumi taste is an enhancement of the intensity of umami, salty and sweet tastes and is a distinct taste modality from the five basic tastes. From human studies, the calcium sensing receptor (CaSR) is the putative receptor for kokumi taste (Maruyama et al., 2012, Ohsu et al., 2010). Kokumi taste perception for cats has not been studied previously, although the cat CaSR receptor sequence is known (Gal et al., 2010). A combined in silico, in vitro and in vivo approach was employed here to study kokumi taste perception of cats using two known ligands of CaSR, CaCl2 and MgCl2, as model compounds. First we developed an in silico model of the cat CaSR based on the solved crystal structure of the human CaSR (Geng et al., 2016) to understand more about the binding mechanism of these divalent cations. The ligands were predicted to bind in the same way to the cat CaSR as to the human CaSR. For the in vitro work, we developed a HEK293 recombinant cell line expressing the cat CaSR and used the assay to measure the binding of CaCl2 and MgCl2. Both compounds were confirmed as agonists and had EC50 values in the low mM range, with Ca2+ having an EC50 value of 1.5 mM and Mg2+ having a slightly higher EC50 value of 6.1 mM. Finally for the in vivo work, we determined if cats had behavioural responses to CaCl2 and MgCl2. These compounds were tested at varying concentrations both individually and in combination with umami compounds to look for potential synergies using a panel of cats at the WALTHAM Centre for Pet Nutrition. The response to both ligands was concentration-dependent, whereby the cats had either a significant preference or no significant difference for CaCl2, while the cats had either a significant aversion or no significant difference for MgCl2. These results suggest that CaSR is involved in cat taste.

(Cyclophosphamide-Induced TnfΑ Expression In The Taste Buds: Cytoprotective Effect Of Amifostine. )
Anish Sarkar1, David Allyn2, Rona Delay3, Eugene Delay4
1The University of Vermont, Burlington, VT, United States, 2University of Pennsylvania, Philadelphia, PA, United States, 3The University of Vermont, Burlington, VT, United States, 4The University of Vermont, Burlington, VT, United States

Chemotherapy is a predominant mode of cancer treatment in patients, often inducing adverse effects such as taste dysfunctions when the drug also affects normal tissues. Disturbances in taste can result in malnutrition, weight loss and further aggravate the condition of the patient during recovery. There could be various reasons for drug-induced taste disturbances such as loss of cells within taste buds, disruptions in taste cell renewal, and tissue inflammation. Our lab has been studying the molecular, cellular and behavioral effects of the chemotherapy drug, cyclophosphamide (CYP). CYP is an antineoplastic, which is a pro-drug and inactive in its native state. Once it is metabolized in the liver by the P450 enzyme complex, its primary metabolite, phosphoramide mustard, functions as an alkylating agent. Our current research is focused on potential CYP-induced inflammation. Specifically, this study is examining the expression of the cytokine TNFα in the taste bud during the 72 h timeline, immediately after injection as well as determine if Amifostine offers any protection to taste buds. Previous research using TUNEL and caspase-3 assays suggests CYP-induced cell loss in fungiform and circumvallate papillae peaks at about 8 and again 18-24 h, post-CYP administration (75 mg/kg, IP). Our present investigation using immunohistochemical analysis suggests that the peak expression of the pro-inflammatory cytokine, TNF-alpha occurs about 8 and 24 hrs post CYP injection in both fungiform and circumvallate papillae. Pre-treatment (100 mg/kg, SC) with Amifostine, appears to decrease the expression of TNF-alpha, indicating the drug can protect the taste system from the alkylating effects of CYP metabolites

Response Properties Of Orosensory Neuron Types In The Mouse Trigeminal Ganglion
Thomas A Myers, Joseph M Breza
Eastern Michigan University, Ypsilanti, MI, United States

An understanding of somatosensory-neuron types innervating the oral cavity is incomplete. Cell bodies of somatosensory neurons innervating the head and neck reside in the trigeminal ganglion (TG). We used in vivo extracellular recording methods in C57BL6J mice to provide a rough stereotaxic map of the TG, to aid in locating orosensory units. Overall, we recorded from 488 single units, the majority of which were from maxillary (V2) and mandibular (V3) divisions. We encountered several somatosensory-neuron types (mechanosensory and thermal) that innervated the skin, vibrissae, lips, tongue, and teeth. Utilizing electrophysiology for guidance, we maneuvered into the oral cavity region of the TG, focusing on units that innervated the tongue and lips. Mechanical force (Von Frey 0.078—39.0mN and glass probe) was used to determine sensitivity and response characteristics (fast or slow adapting). Electrical stimulation was used to determine conduction velocity (CV).  Neurons were tested for thermosensitivity and chemosensitivity via superfusion of the oral cavity with artificial saliva (10°C to 45°C), and allyl isothiocyanate (AITC). Mechanosensory-neurons innervating the lips or anterior tongue fell into two classes based on their CV: C fibers (≤1.2 m/s) or Aδ fibers (≤10 m/s). CV was not an indicator of sensitivity or response characteristics. Many of the mechanosensory units innervating the lips and anterior tongue were highly sensitive (≤0.39mN). 35°C AITC directly activated warm-responsive neurons. In contrast, cool-responsive neurons were unresponsive to 35°C. Interestingly, prestimulation with AITC synergistically modulated warm- and cool-responsive neurons, increasing their thermal-response magnitudes and decreasing thermal thresholds.

The Transient Receptor Potential (Trp) Ankyrin 1 (Trpa1) Ion Channel Contributes To Oral Sensory Avoidance Of Weak Menthol Solutions In Mice.
Jordan E Norris, Christian H Lemon
The University of Oklahoma, Norman, OK, United States

Oral presence of the cooling agent menthol has been discussed to activate both TRP melastatin 8 (TRPM8) and TRPA1 ion channels on trigeminal fibers. Fibers that express TRPA1 typically co-express markers associated with nociceptive processing, whereas such markers appear to be less prominent in or absent from TRPM8-positive neurons. Thus, TRPM8 and TRPA1 may mediate disparate signals related to oral behaviors to menthol. To study this, we used lickometers to measure brief-access licking behaviors to a series of water-soluble, weak concentrations of menthol (0, 0.32, 0.47, 0.7, 1.03, 1.52, and 2.25 mM) in wild-type mice (WT, 30 total) and mice with homozygous deficiency of TRPM8 (M8, n = 10) or TRPA1 (A1, n = 15). Mice initially completed 4 days of sipper tube/brief-access training with water. Partially water deprived mice were then tested with 20, 10 sec presentations of each menthol concentration over 7 consecutive days. Only one randomly-selected menthol concentration was tested daily to mitigate potential carryover effects. Inspection of mean cumulative licks to water revealed all mice elicited >75% of their total licks by the first 5-6 trials of a test session. ANOVA of lick ratios (mean licks menthol / mean licks water) over the first 5 trials revealed WT mice were indifferent to concentrations of menthol =<0.7 mM but showed aversion to menthol at 1.03 mM and higher (P =<0.002). Whereas lick ratios to the menthol series did not differ between M8 and WT mice (P = 0.5), A1 mice showed higher lick ratios than WT for 1.52 and 2.25 mM menthol (Sidak comparisons, P <0.035), indicative of reduced aversion. Thus, TRPA1, but not TRPM8, contributes to aversive oral responding to weak menthol in mice. These data imply TRPM8- and TRPA1-positive trigeminal fibers mediate different orosensory functions. 

Comparative Perceptual Properties Of The Trpa1 Ligand Oleocanthal And The Trpv1 Ligand Capsaicin In The Pharyngeal Area
Catherine Peyrot des Gachons1, Emilie Lescoat1,2, Louise Slade1,3, Gary K. Beauchamp1
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2AgroSup, Dijon, *, France, 3Food Polymer Science Consultancy, Morris Plains, NJ, United States

The ion channel TRPA1 plays a role as a chemosensor, detecting the presence of exogenous irritants and endogenous pro-inflammatory mediators that are implicated in airway inflammation and sensory symptoms like chronic cough, asthma, COPD, allergic rhinitis and cystic fibrosis. When consumed, extra-virgin olive oils high in oleocanthal (OC), a phenolic α,β-unsaturated dialdehyde, evoke an irritation primarily sensed in the throat which can trigger cough. This sensation is highly valued by olive oil connoisseurs as a sign of high-quality olive oil. We have previously shown that OC is a potent anti-inflammatory compound (COX-1 and -2 inhibitor) and its pungency is mediated via activation of TRPA1. To better understand TRPA1 activation in normal conditions in the pharyngeal area and its variation among individuals, we investigated perceptual properties of olive oils containing various amounts of OC in a group of healthy volunteers. We observed great individual variation in OC perceived pungency intensity among the subjects tested over multiple sessions. We also observed neither sensitization nor desensitization of throat pungency upon repeated applications of olive oil at all of the inter-stimuli intervals examined (1, 3 and 10 min). Finally, an olive oil with virtually no OC but supplemented with capsaicin and an olive oil containing OC matched for throat pungency intensity could be qualitatively differentiated: the first one evoked more tingling and the second one more urge to cough and sneeze. We tentatively conclude that individual differences in OC pungency likely reflect differences in TRPA1 activation in the pharyngeal area. Additionally, OC, and most likely other TRPA1 agonists, may be more appropriate agents for cough challenge studies than capsaicin.

Chemesthetic Responses To Allyl Isothiocyanate In Eisenia Hortensis
Mackenzie A Schley1, Thomas A Myers1, Cecil J Saunders2, Wayne L Silver2, Joseph M Breza1
1Eastern Michigan University, Ypsilanti, MI, United States, 2Wake Forest University, Winston-Salem, NC, United States

Allyl isothiocyanate (AITC) is a compound found in several plants of the Cruciferae family, which acts as a repellant to herbivores.  AITC is also responsible for the chemesthetic sensation (chemesthesis) that humans feel when they consume radish, horseradish, mustard, and wasabi. The mechanism for this sensation is thought to be mediated through TRPA1 ion channels. Recent evidence showed earthworms (Eisenia hortensis) use TRPA1 ion channels to detect AITC, which could make them model organisms for the study of chemesthesis.  Earthworms play an essential role in the ecosystem, by improving soil composition and fertility, but little is known about their chemosensory systems. We developed an in vivo extracellular-recording technique that allowed us investigate chemosensory detection in earthworms. Earthworms (n = 27) were placed on a recording block with electrodes inserted near the cerebral ganglion and clitellum. Mechanosensory responses were recorded before and after AITC application to test signal quality. For consistency with previous behavioral experiments, spring water (H2O) was used as the rinse and solvent for all stimuli. The entire body was superfused with solutions at a constant flowrate with a computer controlled delivery system. Following a 60s H2O rinse, a single concentration of AITC (0.05—10mM) was delivered for 20s followed by a 120s H2O rinse. To test for sensitization/desensitization, the same concentration was delivered a second time. The detection threshold for AITC was 0.1mM. AITC response magnitudes increased and response latency decreased systematically with increasing concentration. Responses to 5mM and 10mM were desensitized by 50% and 66%, respectively. To our knowledge, these are the first neurophysiological evidence of AITC chemesthesis in earthworms.

Evidence For Trp Channels In The Earthworm, Eisenia Hortensis.
Karleigh A. Smith, Eileen Reed, Glen B. McKinney, Sopie A. Gonzalez, Patrick M. DeZego, Emily P. Adams, Cecil J. Saunders, Wayne L. Silver
Department of Biology Wake Forest University, Winston-Salem, NC, United States

The earthworm fulfills an important ecological function, yet little is known about their chemical senses– especially how they detect noxious compounds. This sense, known as chemesthesis, is ubiquitous among most animals and is often mediated by transient receptor potential (TRP) channels.  Here we provide evidence for the presence of several TRP channels homologues, including TRPA1, TRPM8, and TRPV1 in Eisenia hortensis, the European nightcrawler. We used a behavioral assay where increasing concentrations of various TRP channel agonists were mixed into the soil. To characterize the repellant nature of the chemical, the number of earthworms that burrowed in the soil--the typical response in control soil--was compared to the number that left the cup. AITC, a TRPA1 agonist, was added to the soil in increasing concentrations, and earthworms were found to leave the cups in a concentration-dependent manner. However, when earthworms were submerged in the TRPA1 channel blocker, H3-030031, the number of earthworms that left the AITC cup was significantly reduced. This same concentration-dependent response was observed when menthol, a TRPM8 stimulant, was added to the soil. For capsaicin, a TRPV1 stimulant, the earthworms did not leave the cup any concentration of capsaicin that was tested. We also identified molecular evidence of E. hortensis TRPA1, TRPM8, and TRPV1-like channels using gene-specific and rapid amplification of cDNA ends (RACE) PCR. We have identified several sequence fragments that are similar to previously reported TRP channel sequences in related organisms. From our behavioral and molecular results, we provide evidence that the earthworm, Eisenia hortensis, uses TRPA1, TRPV1, and TRPM8 channels homologues to detect several respective TRP channel stimulants.

Water Should Not Feel Like Slime: Sensory Acceptability Of Chemesthetic Beverages For Managing Swallowing Disorders
Madison Wierenga, Ciera Crawford, Cordelia Running
Purdue University, West Lafayette, IN, United States

Many older adults suffer from difficulty swallowing thin beverages like water, coffee, or juice. To improve swallowing safety, beverages are typically thickened, which creates a new problem: the thickened beverages are disgusting. New work suggests chemesthesis, particularly intense sourness, spiciness, or carbonation, could improve swallowing without the need for thickeners. Yet, work is needed to assess the palatability of chemesthetic beverages among older adults. Thus, we recruited participants to rate sweetness, sourness, fizziness, stinging, and overall liking of unsweetened carbonated waters (1 plain, 5 flavored), sour orange juice, spicy ginger beer, and colas (sugar or aspartame sweetened). Initial tests (N=30) indicated sour orange juice, spicy ginger beer, and two of the flavored waters were not well-liked, so the other beverages were selected for larger tests (N=64). All the flavored sparkling waters and colas were rated as sweeter than the carbonated water (all p<0.05). Both colas were rated as sweeter than any of the flavored waters, but there was no significant difference in sweetness between colas (p= 0.696). All beverages had a mean liking rating above 2 (Dislike, all p<0.05), and the sugar-sweetened cola had a mean liking rating above 3 (Neutral, p<0.05). Participants liked the colas more than any of the flavored sparkling waters and carbonated water, and liked sugar-sweetened cola more than aspartame-sweetened cola. The stinging of plain carbonated water was marginally greater than diet cola (p=0.051). Further work is ongoing to determine if any of these chemesthetic beverages will effective in improving swallowing safety, as well as to determine if these beverages, despite having relatively low liking ratings in isolation, would be preferable to thickened beverages.

Odor Modulation Of Threat: Fmri-Measured Amygdala Reactivity In Combat Veterans
Bernadette Cortese1,2, Aicko Schumann1, David Houghton1, Thomas Uhde1
1Medical University of South Carolina, Charleston, SC, United States, 2Ralph H. Johnson VAMC, Charleston, SC, United States

     The amygdala exhibits increased activation in response to threat in laboratory animals and across anxiety and stress-related disorders. Common odors, i.e. lavender, may act on the amygdala and, in turn, reduce fear behaviors. We aimed to determine if amygdala reactivity to combat pictures was differentially affected by inhalation of lavender or burning odor. 19 Veterans with posttraumatic stress disorder (PTSD) and 27 healthy Veterans (HV) underwent an fMRI cue-reactivity task during which blocks of combat, nature (neutral), or crosshair (rest) visual cues were presented in combination with either lavender odor, burning odor, or an odorless control. The overall group revealed significant limbic (e.g. amygdala) activation for combat>neutral pictures, and piriform (and amygdala) activation for odors>odorless (all ps <.05). Parameter estimates extracted from amygdala revealed less activation to the combat visual cues during both odors compared to odorless, an effect driven by the PTSD group (left: F[1, 44]=6.5, p<.05; right: F[1, 44]=4.6, p<.05). Our initial hypotheses were partly confirmed. Threat cue-reactivity within the amygdala was attenuated by the lavender odor. However, it was also reduced by the burning odor which was previously shown to increase anxiety in these Veterans. These data suggest a broader role for odors in the modulation of threat, such that general odor processing within the amygdala may interfere with threat processing in that same structure, or that detection of odors in the environment may distract or recruit attentional resources away from those required to process threat. Future studies should replicate these findings, determine the mechanisms that underlie odor modulation of threat, and test the potential therapeutic effects of odors in clinical populations.

Odor Detection Latency And Its Relationship With Attributes Of Liking, Pleasantness And Familiarity
Anshul Jain, Krystyna Rankin, Lalit Damodaran
International Flavors & Fragrances Inc., Union Beach, NJ, United States

Previous research (e.g. Boesveldt et al., 2010; Olofsson, 2012) has shown that odorants systematically differ in terms of how quickly they are detected by humans – the odor detection latency. However, our understanding of how factors such as pleasantness and familiarity affect detection latencies remains limited. There have been conflicting findings with regards to the effect of pleasantness (Boesveldt et al., 2010; Bensafi et al., 2013) while familiarity has only received limited attention (Boesveldt et al., 2010). Moreover, these studies were conducted with a relatively small set of odors (2 – 4) further limiting their generalizability. Therefore, a primary objective of the current study was to fill this gap in knowledge by conducting a systematic study with a large set of iso-intense odors (~30) with a wide range of pleasantness and familiarity ratings as well as other psychophysical and chemical properties. During the experiment, each participant was first trained to synchronize their respiration with a visual stimulus on the computer monitor.  Upon achieving adequate synchronization, the participant began the main part of the study, where a computer-controlled air-dilution olfactometer delivered fragrance ingredients via the cannula to their nose. The participant was instructed to continue synchronizing their respiration with the stimulus and to press a button as soon as they detect a scent (detection latency). The odor was presented at the beginning of an inspiration phase. We also ask participants to report perceived intensity, pleasantness and familiarity for each odorant. Preliminary results show no association between detection latency and pleasantness & familiarity factors. These results along with relationship with other psychophysical and physicochemical properties will be discussed.

Internarial Intensity Difference Serves As A Subconscious Stereo Cue In Human Olfaction
Yuli Wu1,2, Kepu Chen1, Tao Zhang1,2, Wen Zhou1,2
1State Key Laboratory of Brain and Cognitive Science, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Psychology, Chinese Academy of Sciences, Beijing, *, China, 2Department of Psychology, University of Chinese Academy of Sciences, Beijing, *, China

It has been shown that internarial differences serve as directional cues and guide navigation in mammals like rats and moles. Whether this is the case with humans remains controversial, particularly for odors that do not stimulate the trigeminal nerve. Here we demonstrate through formal psychophysical testing that a moderate (4:1), rather than high (5:0) or low (3:2), internarial concentration difference of a non-trigeminal odorant phenyl ethyl alcohol consistently biases participants’ perceived direction of self-motion from visual optic flow towards the higher-concentration side. The effect is obtained despite that the participants are unaware of which nostril receives a higher concentration. We further show that the effect relies on internarial concentration ratio or intensity difference rather than the absolute concentration difference between the two nostrils. Taken together, our findings provide strong behavioral evidence that humans smell in stereo and subconsciously utilize stereo olfactory cues in spatial navigation.

Computation Of Unilateral Odor Intensity Weights Airflow In The Other Nostril
Fangshu Yao1,2, Wen Zhou1,2
1State Key Laboratory of Brain and Cognitive Science, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Psychology, Chinese Academy of Scicences, Beijing, *, China, 2Department of Psychology, University of Chinese Academy of Sciences, Beijing, *, China

Odor intensity is commonly considered as a derivative of the quantity of odor molecules bound to olfactory receptors within a given time window (e.g. a sniff). The current study examines whether airflow also plays a role. In a series of carefully controlled experiments, we ask participants to rate the perceived intensity of unirhinally presented odorants while manipulating the amount of airflow in the other nostril. Odor flow rate and nasal resistance are simultaneously monitored by anterior rhinomanometry. We find that the perceived intensity of a unirhinally presented odor decreases as the amount of pure airflow in the other nostril increases, in manners that are independent of sniff vigor, nasal resistance or attention. Moreover, this phenomenon is due to the sensation rather than the physical amount of nasal airflow, as intranasal spray of a local anesthetic called tetracaine to the other nostril produces the same effect as physically blocking it. Our results suggest that the computation of odor intensity, unlike that of luminance or loudness, is not carried out within a unimodal sensory system but reflects a synergy between the olfactory and the trigeminal systems.

Il-1 Receptor Signaling Promotes The Recovery Of Taste Function After Chorda Tympani Nerve Injury
Lianying He1, Guangkuo Dong2, Lynnette P. McCluskey2
1Medical University of South Carolina, 2Medical College of Georgia at Augusta University, Augusta, GA, United States

Peripheral nerves have the potential to regenerate, but mechanisms responsible for sensory target cell degeneration, regeneration, and reinnervation are poorly understood.  The chorda tympani nerve (CT) and associated taste buds degenerate following nerve sectioning.  Within weeks, however, the CT and fungiform taste buds regenerate and respond normally to taste stimuli in rodent models.  Members of the IL-1 signaling family, important for innate immunity, are prominently expressed in taste buds.  Taste buds are also functionally responsive to IL-1b, which activates the IL-1 receptor.  We tested whether IL-1 receptor signaling affects the regeneration and recovery of neurophysiological responses to taste stimuli.  Robust CT responses to sweet, salty, bitter, umami and acid stimuli were recorded by day 18 post-sectioning in wild-type C57BL/6J mice.  In contrast, IL-1 receptor knockout (IL-1R KO) mice exhibited minimal CT responsivity to tastants through day 36 after injury. Taste bud regeneration and reinnervation by CT fibers was also significantly delayed in the absence of IL-1R.  These results demonstrate the pro-regenerative effect of IL-1 signaling in the peripheral taste system. Current efforts are aimed at discriminating where and when IL-1R signaling is needed to allow the recovery of normal taste function.   

P75Ntr Fails To Co-Localize With Neuronal Markers In The Glomerular Layer Of The Mouse Olfactory Bulb
Rebecca McSorley, Tom Mast
Eastern Michigan University, Ypsilanti, MI, United States

The mouse olfactory system has demonstrated regeneration and plasticity. New sensory axons are guided by olfactory ensheathing cells (OECs), a type of glia, to the olfactory glomerulus where they synapse with mitral and tufted cells. Interestingly, activation of the pan-neurotrophin receptor (p75NTR) by pro-brain derived neurotrophin receptor reduces glomerular tyrosine hydroxylase expression. Thus, we hypothesized that p75NTR signaling in the OECs can regulate synapses within the glomerulus and induce plasticity. However, while OECs are apparent in the olfactory nerve layer, there has been discrepancy as to whether OECs can be found within the glomerular neuropil. In previous experiments we demonstrated p75NTR expression in the neuropil via immunohistochemistry and lesion studies, but were unable to define the cell type that expresses p75NTR. However, p75NTR expression was obvious near sensory axons. In the current experiment we utilize new markers for OECs—brain lipid binding protein (BLBP) and S100beta—and only find minimal co-localization. We conclude that p75NTR is expressed within the neuropil by a sub-set of OECs. Additionally, since some OECs express p75NTR, then these cells may help regulate olfactory synapses.

Reorganization Of Gustatory Inputs Into The Nst Induced In Adult Rats By The Hedgehog Pathway Inhibitor, Sonidegib.
Chengsan Sun1, Archana Kumari2, Charlotte Mistretta2, David Hill1
1University of Virginia, Charlottesville, VA, United States, 2University of Michigan, Ann Arbor, MI, United States

Patients using Hedgehog pathway inhibitor (HPI) drugs experience severe taste dysfunction. The biological basis for the taste disturbance derives from an essential role for Hedgehog (Hh) signaling in taste bud (TB) homeostasis and taste nerve responses: that is, the necessary Hh signaling is abrogated by HPI drugs, and taste organs and sensory functions are disrupted. However, there have been no studies of effects of HPI drugs on central taste circuits. We treated rats aged 8-12 wk for 20 days with oral gavage of an HPI drug, Sonidegib, used by cancer patients, or with Vehicle only. After 18 days, the chorda tympani (CT), greater superficial petrosal (GSP), and glossopharyngeal (GL) nerves were labeled with anterograde tracers to examine the terminal field organization in the nucleus of the solitary tract (NST). Lingual and soft palate TB numbers and immunohistochemistry, and central nerve distributions in the NST, were evaluated. There was a complete loss of TB in fungiform and circumvallate papillae and on the soft palate, but nerves were retained. Elimination of TB in the oral cavity with the HPI drug treatment was accompanied by a selective reorganization of terminal fields in the NST. CT and GSP field volumes were expanded in Sonidegib treatment up to 40% greater than in Vehicle treatment, whereas, terminal field sizes for the GL were similar between groups. The altered terminal fields of lingual nerves demonstrate that central taste circuits are extremely labile at adulthood and sensitive to a profound, albeit short, peripheral taste disruption. Importantly, the alteration in central fields fills a knowledge gap for understanding how HPI drugs alter taste perception in patients who use these treatments: peripheral and central taste circuits are disrupted.

Microglia Play An Important Role In The Pruning Of Primary Gustatory Afferent Terminal Fields In The Mouse Nst
Chengsan Sun1, Fanzhen Kong2, David L. Hill1
1University of Virginia, Charlottesville, VA, United States, 2Binzhou Medical College, Yantai, *, China

Age-related decreases in terminal field sizes occur in the developing gustatory system. The terminal fields of the mouse chorda tympani (CT) and greater superficial petrosal (GSP) nerves in the nucleus of the solitary tract (NST) decrease (i.e., “pruned”) approximately 2X from postnatal day 20 (P20) to P30. The terminal field size of the IX does not change with age. By contrast, mice fed a Na-restricted diet only from embryonic day 3 (E3) to E12 (i.e., Na-restricted mice) show a failure to prune: the terminal fields in adult  Na-restricted mice resemble those of young, control mice. We identified the Classical Complement Cascade as a potential pruning mechanism in control mice. This cascade involves reciprocal signaling between terminals/synapses (i.e., taste afferents) and the immune system (i.e., microglia). To directly address the role of microglia in gustatory circuit development, we asked if attenuating microglia function in postnatal control mice leads to a failure to prune terminal fields, and conversely, if augmenting microglia function in postnatal  Na-restricted mice induces pruning. Through daily injections of minocycline from P15-P40 in control mice, the CT and GSP terminal field volumes were 70%-80% greater than their untreated littermates—they failed to prune. Conversely, through injections of macrophage colony stimulating factor (m-csf) every 3 days from P10-P40, the CT and GSP terminal field volumes in Na-restricted mice were 40%-60% less than their untreated littermates—pruning was induced. These findings provide direct evidence of the involvement of microglia in the maturation of central gustatory circuits, and highlight the high degree of plasticity in the circuit that provides direct gustatory input to the brain.

Molecular Characterization Of Olfactory Neuroblastoma
Matthew Zunitch1, Yaw Tachie-Baffour1, James Schwob1, Eric Holbrook2
1Tufts University School of Medicine, Boston, MA, United States, 2Harvard Medical School, Boston, MA, United States

Esthesioneuroblastoma or olfactory neuroblastoma (ONB) is a rare malignant tumor that typically arises from the cribriform plate region of the nasal cavity and is thought to originate from cells of the olfactory neuroepithelium (OE). Given the capacity of the basal stem cells to regenerate all component cells of the OE either in routine maintenance or in response to injury, perturbations in this regenerative process may result in tumorigenesis. Closer analysis of ONBs with a focus on known markers of OE regeneration can provide insight into the regulation of basal cell differentiation and identify errors in this process that may lead to cancer. We obtained fresh tumor specimens from 6 patients with ONB confirmed with routine histologic staining criteria by clinical pathologists. Immunofluorescence was performed on all six specimens against proteins known to be associated with OE regeneration and differentiation, and bulk RNA sequencing was performed on 4 of the specimens to identify novel tumor markers and define the core ONB transcription factor network. We found that the major constituent cell type of ONB expresses Sox9, beta-Tubulin III, and NeuroD1.  A minor population of Sox2(+) cells with occasional co-expression of CK18 were variably present. Analysis of the transcriptomics revealed a highly correlated network of transcription factors implicated in neuronal differentiation, common to the four specimens despite histological differences. Expression of Dpf1, a neuronal chromatin remodeling complex subunit and the most interconnected node within the network, was validated on the protein level and may represent a novel tumor marker and core transcriptional regulator in the pathogenesis of ONB.

Impact Of Constitutive IA And Gabaergic Inhibition On Solitary Nucleus Output Using Optogenetics And Dynamic Clamp
Zhixiong Chen1, Cameron Conte2, Trevor Haas1, Andrew Harley1, Alison Boxwell3, David Terman4, Susan Travers1, Joseph Travers1
1Ohio State University College of Dentistry, Columbus, OH, United States, 2Yale University Dept. of Neuroscience, New Haven, CT, United States, 3Ohio State University College of Medicine, Columbus, OH, United States, 4Ohio State University Department of Mathematics, Columbus, OH, United States

Output from the rostral (gustatory) nucleus of the solitary tract (rNST) is modified both by GABAergic inhibition and constitutive ion channels expressed on projection neurons. Previous work suggested that projection neurons expressing the hyperpolarization-sensitive IA channel were particularly sensitive to GABAergic inhibition (Chen et al., ’16). In the present study, we dissociated the impact of IA and GABAergic inhibition on the output of projection neurons in response to afferent (solitary tract, ST) stimulation using whole cell patch clamp and pharmacological suppression of IA with and without GABAergic inhibition induced optogenetically. We identified the K+ channel sustaining IA as belonging to the Kv4 family by its near total suppression by the channel blocker AmmTx3, and further specified the channel as KV4.3 immunohistochemically. Although optogenetic release of GABA significantly suppressed output in cells with IA, pharmacologic block of IA did not significantly change the degree of inhibition. In cells with IA, however, we further observed that blockade of IA with AmmTx3 significantly increased ST-evoked rNST responses. Moreover, preliminary results using dynamic clamp suggest that adding IA to projection neurons suppresses output. We speculate that IA plays multiple roles in regulating projection neuron excitability. The presence of KV4.3 in distal dendrites may act to blunt excess excitability resulting from convergence of excitatory afferent input to projection neurons, as has been suggested for other systems. In addition, because IA expression can be affected by diet and other homeostatic conditions, this channel may modulate taste neuron excitability to reflect metabolic state.

Gastric Bypass Alters Glutamate Levels And Release To Oral Sucrose In The Rostral Nts Of The Rat
Andras Hajnal1, Elise Orellana1, Patricia M. Di Lorenzo2, Krzysztof Czaja3
1Department of Neural and Behavioral Sciences, Penn State University, College of Medicine, Hershey, PA, United States, 2Department of Psychology, Binghamton University, Binghamton, NY, United States, 3Veterinary Biosciences and Diagnostic Imaging, University of Georgia, Athens, GA, United States

Roux-en-Y gastric bypass (RYGB), the most effective method to achieve long-term weight loss, reverses enhanced preference and intake of sweet foods. Recent studies suggest neuronal plasticity occurs in the rotral nucleus of the solitary tract (rNTS), the first central gustatory relay, following RYGB. The current study investigated if RYGB had an effect on glutamate (Glu) levels within rNTS. Male Sprague Dawley rats (n=12), fed a high energy diet (60%kcal fat) for 8 weeks, received RYGB or SHAM surgeries. Four weeks later, 15-min microdialysis samples were collected from the rNTS prior, during and after 15-min access to a 0.6M sucrose solution (Days 1 and 2) or water (Day 3). From the microdialysis samples 13C-benzoyl chloride-derivatized Glu was analyzed using a UPLC/MS system. Baseline Glu levels (i.e., prior to sucrose) were significantly higher in RYGB rats compared to SHAM (210±48 vs 86±27 pg/µl sample, p<0.05). On Day 1, novel 0.6M sucrose reduced Glu levels in both SHAM and RYGB cohorts equally (to 59±8%, and 64±6% of baseline). On Day 2, consumption of the familiar sucrose solution reduced rNTS Glu efflux in the SHAM but not in the RYGB rats (74±14% and 111±13% of baseline). Conversely, on Day 3, drinking water resulted increased Glu in SHAM (159±24% of baseline, p<0.05) but again no change in RYGB rats (104±22% of baseline). These neurochemical observations are in concert with findings from our ongoing electrophysiological studies suggesting that RYGB may alter central gustatory processing by decreasing the magnitude of taste-evoked neuronal activity. Since baseline levels of Glu in RYGB are higher than in SHAM rats, the system may be able to respond only to a very strong stimulus, like a combined novel and sweet solution.

Responses To Left- And Right-Sided Olfactory Stimuli: An Investigation Based On Psychophysical And Electrophysiological Data
Thomas Hummel, Susann Fraesdorf
Smell and Taste Clinic, Dept. of ORL, Dresden, *, Germany

Objectives: The study aimed to investigate differences in the processing between monorhinal and birhinal stimulation. Methods: 34 right-handed volunteers participated. Normal olfactory function was ascertained using the “Sniffin’ Sticks” tests. An olfactometer was used that delivered stimuli (air-dilution olfactometry). Participants rated intensity of the stimuli separately for the left and right nostril. Event-related potentials were recorded for olfactory (phenyl ethyl alcohol) and trigeminal stimuli (CO2). Stimuli were presented in 7 classes with different concentrations to either the left or right nostril or to both nostrils simultaneously. Results: Results for the lateralisation of chemosensory stimuli matched results from previous work, in that subjects were unable to localize olfactory stimuli at any of the various stimulus conditions, whereas trigeminal stimuli could be easily localized, except for lower CO2-concentrations. Most interestingly, intensity ratings for the birhinal olfactory stimuli suggested a super-additive effect in comparison to monorhinal olfactory stimulation. No such effect was seen for trigeminal stimuli, where the highest concentration at either side determined the rated intensity. The psychophysical results were confirmed by electrophysiological recordings indicating that in the olfactory system bilateral summation occurs, at very early stages of processing. Conclusions: The present results indicate a significant role of spatial summation processes for the birhinal perception of suprathreshold odor stimuli. They also emphasize the somato-sensory nature of trigeminal stimuli where the site of stimulation is encoded in the stimulus information.

Effects Of Manipulating The Activity Of Amygdala Somatostatin-Expressing Neurons During Concentration-Dependent Licking Of Sucrose And Quinine Solutions.
Robert F Lundy
University of Louisville School of Medicine, Louisville, KY, United States

We have known for decades that the gustatory region of the nucleus of the solitary tract (NST) and parabrachial nucleus (PBN) are densely innervated by forebrain structures like the central nucleus of the amygdala (CeA).  Chemical or electrical stimulation of the CeA modulates responsiveness of NST and PBN neurons to sapid stimuli indicating active filtering of gustatory information.  Yet, the functional consequences of such neuromodulation with respect to the control of taste-guided behavior remains unknown.  My previous research has shown that the gustatory NST and PBN are major targets of non-overlapping populations of CeA neurons that express somatostatin (Sst). The present research uses optogenetic retrograde gene transfer techniques to assess the role of target-specific/Sst-CeA neurons in the control of taste-guided behavior.  Mice that express Cre-recombinase in Sst neurons received bilateral injections into the NST or PBN of a cre-dependent virus that infects axon terminals and is retrogradely-transported back to the parent cell body.  The virus encodes: 1) enhanced yellow fluorescent protein (EYFP) and an excitatory light-activated ion channel (ChR2), 2) EYFP and an inhibitory light-activated ion channel (eNpHR3.0), or EYFP alone.  Bilateral optic fiber cannulas chronically implanted above the CeA allowed for the activation or inactivation of target-specific/Sst-CeA neurons during brief-access licking of various concentrations of sucrose and quinine solutions.  I hypothesize that manipulating Sst/CeA-to-NST cell activity will have a greater influence on concentration-dependent intake of sucrose and quinine compared to manipulating Sst/CeA-to-PBN cell activity.

Gustatory Activity In The Rat Parabrachial Nucleus Following Neonatal Chorda Tympani Transection
Louis J. Martin, Suzanne I. Sollars
University of Nebraska at Omaha, Omaha, NE, United States

Peripheral taste input is important for the structural development of the gustatory brainstem, but the role of taste information in shaping the brain’s functional development is less clear. Chorda tympani transection (CTX) in neonatal rats results in permanent absence of gustatory input from the anterior tongue. Neonatal CTX also causes long-term reduction in glossopharyngeal activity to NaCl and an abnormal adult preference for ammonium chloride (NH4Cl). It is unclear what changes in the brain are associated with these alterations in nerve activity and behavior. In the current study, we recorded activity of single neurons in the parabrachial nucleus of the pons (PbN) after neonatal CTX in male and female rats. At 5 days of age, the chorda tympani was assessed via the ventral neck and either transected (CTX) or left intact (Sham). After rats reached adulthood, electrophysiology was performed under urethane anesthesia. In all animals, the chorda tympani was transected in the middle ear immediately prior to recording to ensure that all sampled neurons received input from taste buds innervated by the glossopharyngeal and/or greater superficial petrosal nerves. Rates of firing were assessed in response to 0.1-0.5 M NH4Cl, 0.1-0.5 M NaCl, 0.5 M sucrose, 0.01 M citric acid, and 0.01 M quinine. Initial results show that rats given neonatal CTX had significantly higher firing rates to 0.1 M NaCl compared to Shams. Since the glossopharyngeal nerve has very little response to this concentration of NaCl, this finding suggests that signals from the greater superficial petrosal to NaCl may be amplified in the PbN after early CTX. Responses to other stimuli were not significantly different between experimental groups. Neonatal CTX may alter taste-elicited activity of PbN neurons in a stimulus-specific manner.

Optogenetic Excitation Of Lateral Hypothalamic Input To The Nucleus Of The Solitary Tract Modulates Non-Taste Neurons And Licking Behavior In The Awake Rat
Joshua D Sammons1, Caroline E Bass2, Jonathan D Victor3, Patricia M Di Lorenzo1
1Dept. of Psychology, Binghamton University, Binghamton, NY, United States, 2Dept. of Pharmacology and Toxicology, University at Buffalo, SUNY, Buffalo, NY, United States, 3Feil Family Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY, United States

The functional significance of projections from the lateral hypothalamus (LH) to the nucleus of the solitary tract (NTS) is largely unknown. Here, we used optogenetic tools to selectively enhance LH-NTS input while rats freely licked. We infused viral constructs containing Channelrhodopsin 2 (ChR2) bilaterally into the LH of rats. After 2-4 wks, we implanted an optrode (fiber optic cable with 8-16 tungsten microwires) into the taste-responsive portion of the NTS and allowed the rats to recover. With moderate water deprivation, rats were given trials of 5 licks of a tastant (0.1 M NaCl, 0.1 M sucrose, 0.1/0.01 M MSG/IMP, 0.01 M citric acid, 0.1 mM quinine, 0.1 M KCl, 0.1 M NH4Cl, or artificial saliva, randomly presented) separated by 5 rinse licks presented on a VR5 schedule. Optical stimulation (25 Hz of 473 at 8-10 mW) accompanied a random half of the trials. Results from 20 taste cells showed that optical excitation of LH-NTS input affected response magnitudes resulting in an increase in information conveyed to distinguish palatable vs. non-palatable tastants. Optical stimulation of LH-NTS input alone decreased the spontaneous firing rate of 7 (of 30) non-taste cells but had no effect on NTS taste cells. After several weeks of taste-only recording, rats were switched to a Go/no-Go (GnG) paradigm. A single cue stimulus lick (0.1 M NaCl, 0.1/0.01 M MSG/IMP or 0.1 M KCl in separate sessions) was followed by 5 dry licks, 3 licks of a test stimulus (0.1 M NaCl, 0.1/0.01 M MSG/IMP, or 0.1 M KCl) and a 1 s timeout.  If cue and test stimuli matched, continued licking produced a 3-lick 0.5 M sucrose reward. If they differed, the rat was required to withhold licking for 1 s or be punished by 3 licks of 2 mM quinine and a 5 s timeout. In a random half of each trial type, each test lick triggered 1 s optical stimulation. Following a correct rejection, LH-NTS excitation prolonged the suppression of licking. In some cases, enhancing LH-NTS input attenuated the normal lick suppression following a quinine punishment. These data suggest that LH-NTS input may modulate behavior by influencing the neural representation of palatable vs. no-palatable taste stimuli.

Is The Sexual Dimorphism Of The Olfactory Bulb The Same In Different Mink Races (Neovison Vison Var. Spec.) ?
Willi Bennegger1,2, Elke Weiler3
1Maria-von-Linden-Schule, Heckentalstraße 86 , D-89518 Heidenheim, *, Germany, 2Faculty of Natural Sciences, Institute for Neurobiology, University of Ulm , D-89081 Ulm, *, Germany, 3Max-Planck-Institute for Biological Cybernetics, Max-Planck-Ring 8 , D-72076 Tübingen, *, Germany

Sexual differences are observed in many neural structures, including the olfactory bulb. However, the olfactory bulb structure is also influenced by genetic variations defining the coat color. So we were interested if the sexual dimorphism of the olfactory bulb is the same in the different races of the American mink. Therefore we investigated the absolute volume of the different layers in both sexes of four color variations in the mink (“standard” Neovison vison var. atratus, a; “silverblue” Neovison vison var. glaucus, g; “pastel” Neovison vison var. suffuscus, s ; “wild” Neovison vison var. carinum, c). The results show that the absolute volume of the olfactory bulb is smaller in females (f) compared to males (m) in all races with values of 71-81% (f/m). The sex ratio of the different layers however show a much greater variation among the races. The fila layer of atratus females has only 46% of the male volume whereas the other races have 60-62%. In the glomerular layer, atratus females have 71% compared to 82-90% in suffuscus and glaucus. The external plexiform layer has higher sex ratios of 84-88% in a and g versus 76% in s and c. The most striking effects are seen in the IPL  and subependymal layer where suffuscus females have even higher volumina than males (104-110%) while the other races have values of 51-81% in the IPL and 72-89% in the subependymal layer. The sex ratio of the granule cell layer is 94-97% in a and s versus 75-86% in c and g. The stratum album sex ratio is 67-74% in a and c versus 80-88% in s and g. The results indicate that there is no uniform sexual dimorphism but the genetic factor of the race is inducing a layer-specific sexual dimorphism.  

Recovery And Morphological Remodeling Of The Zebrafish Olfactory Bulb Following A Focal Excitotoxic Lesion
Erika Calvo-Ochoa, Christine A. Byrd-Jacobs
Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, United States

Brain lesions are the leading cause of long-term disability worldwide. Patients suffering from these lesions frequently present incomplete recovery, since adult mammalian brains have a limited repair capacity following damage. On the other hand, zebrafish (Danio rerio) has an extraordinary regenerative potential since it effectively repairs brain lesions throughout the lifespan. The olfactory bulb is a highly plastic brain region that swiftly adapts in response to odors and to damage to the peripheral olfactory organs; however, the recovery and morphological remodeling of the zebrafish olfactory bulb following direct injury has not been studied. In this work we establish a new paradigm of focal excitotoxic lesion in the zebrafish olfactory bulb and investigate the recovery and remodeling of the lesioned olfactory bulb in time. We used adult zebrafish of both sexes and produced a focal excitotoxic lesion in the right olfactory bulb by injecting 1 µl of 15mM quinolinic acid (QA). We performed histological, immunohistochemical, stereological and morphological analyses of olfactory bulb sections following 1, 7, 15 and 21 days post lesion (dpl) in order to study damage, repair and morphological remodeling parameters following lesion. Although the exact location of the lesion varied, all lesioned bulbs exhibit a consisting wound of similar volume. Our results show that a QA focal excitotoxic lesion greatly damages the olfactory bulb and significantly reduces its volume at 1 dpl, and that complete volume recovery is achieved at 21 dpl. Other histological and cellular markers of recovery occur in the lesioned olfactory bulb in a time-dependent fashion. To our knowledge, these results are the first to report a time-course characterization of the recovery of the lesioned olfactory bulb in zebrafish.

Restoring The Sense Of Smell: The Development Of An Olfactory Implant System
Daniel H Coelho1,2, Richard M Costanzo1,2
1Department of Otolaryngology Head & Neck Surgery, Virginia Commonwealth University, Richmond, VA, United States, 2Department of Physiology and Biophysics, Virginia Commonwealth Univerisity, Richmond, VA, United States

Despite its prevalence and impact on quality of life, no viable treatments exist for the treatment of anosmia.  To address this, our lab has been exploring the use of direct electrical stimulation of the olfactory bulb as a novel method to bypass damaged olfactory nerves to restore olfactory function. The ability to directly stimulate areas of the brain to activate losses of sensory percept is not without precedent. Cochlear, auditory brainstem, and retinal implants are only some of the increasingly common treatment options for those with loss of a special sense.  The Olfactory Implant System (OIS) prototype consists of gas sensors, a microprocessor and an electrode array for direct stimulation of the olfactory system.  Preliminary data using a rat olfactory nerve injury model shows that stimulation at different positions along the ventral surface of the bulb generates different patterns of evoked potentials activity recorded at the dorsal surface.  By programming varying simulation patterns within the electrode array (similar to that used with cochlear implants), it should be possible to selectively activate different regions of the olfactory bulb, generating unique patterns of neural activity that lead to smell perception.  Although in the early stages of development, the Olfactory Implant System (OIS) may ultimately do for acquired anosmia what the cochlear implant has done for sensorineural hearing loss.

Target Specific Functions Of Epl Interneurons In Olfactory Circuits
Gary Liu2,4,5, Emmanoil Froudarakis3, Jay Patel3,4, Mikhail Kochukov1, Brandon Pekarek1, Patrick Hunt1,4, Mayuri Patel2, Kevin Ung2, Annie Fu3, Juyeong Jo3, Hyun-Kyoung Lee3,5, Andreas S. Tolias3, Benjamin R. Arenkiel1,2,3,5
1Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, TX, United States, 2Program in Developmental Biology, Baylor College of Medicine, Houston, TX, United States, 3Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States, 4Medical Scientist Training Program, Baylor College of Medicine, Houston, TX, United States, 5Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX, United States

Inhibitory interneurons play prominent roles in sensory processing, yet their target-specific functions in sensory circuits remain largely unknown. Investigating the mouse olfactory system, we selectively removed GABA transmission from a subset of olfactory bulb interneurons, and assayed odor responses from their downstream synaptic partners — Tufted cells and Mitral cells. Using a combination of in vivo electrophysiological and imaging analyses, we found that inactivating this single node of inhibition leads to cellular changes in Mitral/Tufted cell odor responsivity, with differential effects in intensity, reliability, tuning, temporal dynamics and mixture coding between the two principal neuron cell types. Together, our data suggest that olfactory bulb interneurons, through exerting distinct inhibitory functions onto their different synaptic partners, can increase the dimensionality of sensory processing. 

Olfactory Bulb Atrophy In H&Y Stage-1 Parkinson&Rsquo;S Disease
Jianli Wang, Rachel S Stanford, Lauren Spreen, Thyagarajan Subramanian, Qing X Yang
Penn State College of Medicine, Hershey, PA, United States

Objective: To investigate whether there is olfactory bulb (OB) atrophy in H&Y stage-1 Parkinson’s disease (PD). Introduction: Hyposmia has been reported to occur in the majority of early-stage PD patients. Postmortem studies show that the OB is highly affected by Lewy pathology. However, whether there are OB morphological changes in early-stage PD is not clear. We hypothesized that there is detectable OB atrophy in H&Y stage-1 PD patients.   Methods: 17 idiopathic stage-1 PD participants and 14 age/sex-matched HCs participated in this study. Smell detection thresholds and identification function of each subject were obtained. Each nostril was assessed separately. MRI was conducted on a 3T scanner with a 64-channel coil. OB volumes of left and right sides were measured via manual segmentation by two raters blinded to patient status and olfactory scores. Analysis of OB volume was performed with both absolute as well as intracranial volume (ICV) normalized volumes. Cross-cohort comparisons were conducted using ANOVA with multiple comparisons and age/sex as covariates in SPSS. The two sides were compared with paired t-test.    Results: Scores of smell threshold and identification tests were significantly lower in stage-1 PD patients compared to those of HCs. Comparison of OB volumes revealed significant OB atrophy in PD when using absolute OB volume values and ICV normalized volumes. There were no significant differences between left and right side in smell functions or OB volumes in either group. Conclusion: Results from the psychophysical tests of smell functions demonstrate significant smell deficits in H&Y stage-1 PD patients. In alignment with reduced smell functions, OB volume was found to be reduced in PD patients. These findings support the hypothesis that there is OB atrophy in H&Y stage-1 PD.

Reversible Unilateral Anosmia Postictally In A Patient With Frontotemporal Lobe Epilepsy
Patrick Doerig1, Stephan Rueegg2, Antje Welge-Luessen1
1Department of Otorhinolaryngolog, University Hospital of Basel, Basel, *, Switzerland, 2Department of Neurology, University Hospital of Basel, Basel, *, Switzerland

Objective: Olfactory disorders are common in neurodegenerative diseases and can also be found in subjects with temporal lobe epilepsy (TLE). In TLE odor identification is often slightly impaired and additionally both olfactory auras and olfactory prodromal symptoms may be present. Even though transient loss of neurological functions after seizures is a well known phenomenon postictal olfactory dysfunctions are very rare.  We report on a patient with focal refractory epilepsy suffering from postictal olfactory dysfunction and review the literature.  Methods: A 36 years old patient suffering from focal, likely lesional pharmacoresistant epilepsy, complained about a distorted, severely reduced sense of smell 1-2 days after seizures, resolving back to normal within a few days. Endoscopic endonasal examination was performed and besides EEG and magnetic resonance imaging - olfactory function (each nostril separately) was evaluated using the extensive Sniffin´ Sticks test battery. Threshold (T), Discrimination (D) and Identification (I) was measured and a composite TDI score was calculated. Results: Endonasal examination was normal, except for a slight septal deviation to the right. First olfactory testing, three months after last seizures, without subjective disturbance, showed a TDI score of 23.5 right (hyposmia) and 30.75 (normosmia) left. The second examination was performed 2 days after the seizures (patient complaining of olfactory impairment and parosmia) and revealed a TDI score 21.75 right and 15 (anosmia) left, four days later subjective complaints had disappeared and TDI score was 37.25 right and 36 left. Conclusion: Olfactory complaints postictally have to be taken serious and may be due to a postictal olfactory impairment which we have been able to document in a patient with TLE.

Top-Down Olfactory Processing In Subjects With Olfactory Loss
Akshita Joshi, Pengfei Han, Thomas Hummel
Technical University of Dresden Medical School, Dresden, *, Germany

Objective: To investigate top-down olfactory processing in patients with congenital (CA) or idiopathic anosmia (IA) in comparison to normosmic controls (NC) during expectancy and reading of odor associated words. Method: We investigated 3 different groups: CA (n=14) with a life-long inability to smell; IA with past experience of smell (n=8) and NC (n=16). Within the MR scanner (3T, Siemens Prisma) participants were shown words with or without olfactory associations, e.g. banana or a chair. Blocks with odor-associated words were alternated with blocks of neutral words. Data was analyzed in terms of (A) expectancy (instruction to read odor- associated words) and (B) response when reading odor associated words. Results: For analysis A, expectancy, NC and IA subjects showed more activations as compared to CA participants in the anterior cingulate gyrus along with the middle frontal gyrus of prefrontal cortex. For analysis B, overall CA patients exhibited more activation in the right insular cortex and right caudate compared to IA and NC. Conclusion: Neuroimaging results suggest a group difference during expectancy and reading of odor related words. IA and NC subjects show more activation in anterior cingulate gyrus and in the middle frontal gyrus, suggesting their olfactory related experience. On the other hand, activations in CA patients seem to indicate that the anterior insular cortex is strongly involved in the processing of olfactory information even if there was no previous experience with odorous stimuli.

An Italian Population-Based Study Of The Prevalence Of Olfactory Impairment
Carla Masala1, Annachiara Cavazzana2, Eugenio Aprea3, Monica Borgogno4, Elena Cantone5, Andrea Ciofalo6, Serena Drago 4, Flavia Gasperi 3, Alberto Macchi 7, Leonardo Menghi 3, Valentina Parma 8, Maria Piochi9, Raffaella Piras1, Benedetta Pasquariello6, Luisa Torri9, Thomas Hummel2
1Department of Biomedical Sciences, University of Cagliari, Cagliari, *, Italy, 2Department of Otorhinolaryngology, Smell and Taste Clinic TU Dresden, Dresden, *, Germany, 3Research and Innovation Centre, Edmund Mach Foundation, San Michele all’Adige, , Trento, *, Italy, 4Mérieux NutriSciences Italia, Prato, *, Italy, 5Neurosciences, Reproductive and Odontostomatologic Sciences, Unit of Ear, Nose and Throat, Federico II University , Naples, *, Italy, 6Department of ‘Organi di Senso’, University “Sapienza”, Roma, *, Italy, 7ORL Clinica, Università of Insubriae Varese, ASST Settelaghi, Varese, *, Italy, 8SISSA, Neuroscience Area, Trieste, *, Italy, 9University of Gastronomic Sciences, Pollenzo, Cuneo, *, Italy

The loss of sense of smell decreases quality of life and may contribute to the failure in recognizing hazardous substances. Given the relevance of olfaction in the daily life, it would be important to recognize undiagnosed olfactory dysfunction in order to prevent these possible complications. Up to now, the prevalence of smell disorders in Italy is unknown because of a lack of epidemiological studies. The aim of the present study is to present the current data on the prevalence of olfactory dysfunction in an Italian sample to provide random, population-based data of olfactory dysfunction in adults, based on psychophysical testing and to relate dysfunction to age, sex, cognitive abilities, cognitive reserve and depression level. A total of 703 participants (mean age: 50.6; SD: 19.5; range: 18-94) from eight different Italian regions took part in the study. The sample was stratified in proportion to sex and six age groups: 18-29 (N = 127); 30-39 (N = 115); 40-49 (N = 105), 50-59 (N = 115), 60-69 (N = 89); >70 (N = 152). Olfactory function, cognitive abilities, cognitive reserve and depression were assessed respectively with: “Sniffin’ Sticks” Identification Test, Montreal Cognitive Assessment, Cognitive Reserve Index and the Beck Depression Inventory. Additionally, sociodemographic data, medical history, and health-related lifestyle information was collected. About 38% of our sample presented olfactory impairments. Multiple regression analysis revealed that age, sex, cognitive abilities, cognitive reserve and depressive symptoms explained a total of 28.5% of the variance in olfactory scores. Higher odor identification scores were associated with female sex, lower age, higher level of cognitive functioning, higher cognitive reserve but, surprisingly, more depressive symptoms.  

Presence Of Undetected Olfactory Loss In The General Population - Based On A Large Sample Of 9139 Subjects
Anna Oleszkiewicz1,2, Ilona Croy1, Valentin Schriever1, Antje Haehner1, Thomas Hummel1
1TU Dresden, Dresden, *, Germany, 2University of Wroclaw, Wroclaw, *, Poland

Presented data were analyzed to provide up-to-date and more detailed normative data based on a large-scale sample to increase validity of the diagnosis by creating the possibility to refer individuals to more narrow age-groups. Previous normative values lacked higher sample sizes especially in the group of older subjects. Data was obtained from 9139 subjects, of whom 4928 were females aged 5 – 96 years (M=31.8, SD=18.9) and 4211 were males aged 5 - 91 years (M=30.7, SD=17.7). All subjects were healthy. They were tested with a standard “Sniffin’ Sticks” test comprising Threshold, Discrimination and Identification subtests. With this extended sample, we found hyposmia to be defined as less than 30.75 points of the TDI score. We confirmed age-related changes in each domain, but it was most pronounced for threshold. Individuals aged 20-30 years showed the highest values, while children below the age of 10 and adults above the age of 71 performed only half as well. Sex-related differences were in favor for women. Importantly, in this sample of relatively young and healthy people we found a meaningful proportion of subjects scoring in the range of hyposmia or functional anosmia, who seem not to be aware of the olfactory dysfunction or seem not to be bothered by it. Their demographical characteristic will be presented together with detailed olfactory scores.  

Olfactory Cilia Defects From A Single Point Mutation In Bbs1 Result In Impaired Odor Detection And Perception In A Bardet-Biedl Syndrome Mouse Model
Chao Xie*1,2, Julia Habif*1,2, Cedric Uytingco1,2, Kirill Ukhanov1,2, Lian Zhang1,2, Val Sheffield3,4, Jeffrey Martens1,2
1Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, FL, United States, 2Center for Smell and Taste, University of Florida College of Medicine, Gainesville, FL, United States, 3Department of Ophthalmology,University of Iowa Carver College of Medicine, Lowa City, IA, United States, 4Department of Pediatrics, University of Iowa Carver College of Medicine, Lowa City, IA, United States

Bardet-Biedl syndrome (BBS) is a hereditary genetic disorder that results in numerous clinical manifestations including olfactory dysfunction.  BBS proteins are critical for ciliary protein trafficking and cilia maintenance. Of at least 19 BBS related genes which can carry multiple mutations, a single pathogenic mutation, BBS1 M390R, accounts for the majority of clinically diagnosed BBS outcomes. The penetrance of olfactory dysfunction induced by the BBS1 M390R mutation remains unclear. Using a mouse model homozygous for BBS1 M390R, we investigated the impact of the mutation on the olfactory system. The olfactory cilia of olfactory sensory neurons (OSNs) in Bbs1M390R mice (average cilia length: 13.0±1.0μm; average cilia number: 6.6±0.6 cilia/OSN) were significantly shorter and fewer than wildtype mice (length: 30.6±3.2μm; number: 23.8±1.1cilia/OSN). Also, cellular odor detection as measured by electroolfactogram was significantly decreased in the Bbs1M390R mice. Traditional operant-based assays to measure odor discrimination and detection thresholds, cannot be performed in cilia deficient mice as they are severely olfactory impaired and thus cannot learn an odor-association task. To circumvent this issue, we used whole-body plethysmography to directly measure odor-evoked sniffing combined with a cross-habituation assay to provide a robust and sensitive behavioral platform to quantify odor perception.  The Bbs1M390R mice showed significantly higher odor detection thresholds (reduced odor sensitivity) compared to wild-type mice. Together, our findings demonstrate the penetrance of the BBS1 M390R mutation in OSN cilia and provide a clinically relevant model for the development of gene therapy treatment for congenital ciliopathies in the olfactory system.     

Deciphering The Responses Of Skin-Penetrating Nematodes To Carbon Dioxide.
Navonil Banerjee, Spencer Gang, Elissa Hallem
University of California Los Angeles, Los Angeles, CA, United States

Skin-penetrating nematodes are gastrointestinal parasites that infect nearly one billion people worldwide. They respond robustly to a wide range of sensory cues. However, the specific roles of host-associated chemosensory cues in driving parasite-host interactions are poorly understood and the mechanisms underlying detection of such cues have not been investigated. We are studying the role of carbon dioxide (CO2) in promoting host-parasite interactions using the human-skin-penetrating threadworm Strongyloides stercoralis. Specifically, we are elucidating the role of COin mediating three crucial steps of the parasite-host interaction: (a) host seeking, (b) development inside the host after skin penetration (activation), and (c) migration within hosts to complete the parasitic life cycle and establish an infection (intra-host navigation). We show that behavioral responses to COdiffer across life stagesWhile infective larvae (iL3s) are repelled by CO2, activated iL3s are attracted and free-living adults are neutral to CO2. COis also critical for triggering activation. COrepulsion by iL3s may function as a dispersal cue, driving them off host feces and into the soil to host seek. Once inside the host, COattraction may direct activated iL3s to the host small intestine. We are now using CRISPR/Cas9-mediated targeted mutagenesis to identify genes required for CO2response in parasitic nematodes. We have found that the receptor guanylate cyclase GCY-9 mediates CO2-evoked responses in S. stercoralis, and that the S. stercoralis BAG neurons detect CO2. We are now investigating the neural mechanisms that enable S. stercoralis to generate life-stage-specific responses to CO2. Our results will provide insight into the chemosensory mechanisms that drive host-parasite interactions.

Expression Of The G Protein Coupled Odorant Receptors
Claire A de March1, Kentaro Ikegami 1,2, Maira H Nagai1,3, Soumadwip Ghosh4, Matthew Do 1, Ruchira Sharma 1, Elise S Bruguera 1, Yueyang Eric Lu1, Yosuke Fukutani 1,2, Nagarajan Vaidehi 4, Masafumi Yohda 2, Hiroaki Matsunami1,5
1Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, United States, 2Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo, *, Japan, 3Universidade de Sao Paulo, Sao Paulo, *, Brazil, 4City of Hope, Department Computational and Quantitative Medicine, Beckman Research Institute, Duarte, CA, United States, 5Department of Neurobiology, Duke Institute for Brain Sciences, Duke University Medical Center, Durham, NC, United States

Odor perception is based on odorant receptors, which belong to the large family of G protein-coupled receptors. This receptor family switch from an inactive to an active state when bound to an agonist odorant. It is widely accepted that the activation of these odorant receptors is responsible for the perception of odors. However, the vast majority of odorant receptors show poor cell surface expression in non-olfactory cells due to retention of the endoplasmic reticulum (ER), hindering their structural elucidation and functional study. Here, we study at the molecular level the expression mechanisms of this sub-family of G protein coupled receptors. We use the diversity of the odorant receptor repertoire to create new optimized synthetic receptors based on their consensus residues. We also used two odorant receptors possessing a large sequence identity but different level of expression. Using these two test cases, we study the role of amino acids in their expression through molecular modeling, site directed mutagenesis and flow cytometry. Their functionality is also assessed by in vitro assays. Our data supports the idea that intrinsic structural instability of odorant receptors underlies ER retention. This research is crucial, not only to understand the strategy of our brain to perceive its olfactory environment, but also to identify general mechanisms governing the function of odorant receptors and open the door to their structural elucidation.

Identifying Key Olfactory Receptors In Odor Perception Using Machine Learning
Marissa L. Kamarck1,2, Casey M. Trimmer1, Andreas Keller3, Lindsey L. Snyder1, Nicolle R. Murphy1, Leslie B. Vosshall3,4,5, Joel D. Mainland1,2
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2University of Pennsylvania, Philadelphia, PA, United States, 3The Rockefeller University, New York, NY, United States, 4Howard Hughes Medical Institute, New York, NY, United States, 5Kavli Neural Systems Institute, New York, NY, United States

The olfactory system combines input from multiple distinct receptors to represent odor information, but there are few, if any, explicit predictions relating olfactory receptor (OR) activity patterns to odor perception. Previous work from our lab compared genetic variation in ORs to differences in odor perception using univariate genotype-phenotype association analyses, as is standard practice in genomics. This analysis has low statistical power and is not informed by genetic interactions that are particularly important in olfaction, where an odor percept is likely influenced by multiple receptors. Here we use machine learning techniques that are better suited to uncovering multi-receptor interactions amongst a large number of variables (genetic variants). We asked 540 participants to rate the intensity and pleasantness of nine musk compounds, and we sequenced their ORs to identify genetic variants. We compared performance of a traditional linear model that used the best-associated OR with a random forest (RF) model that used ~200 of the most important genetic variants to predict the intensity or pleasantness rating. The RF model reliably outperformed the linear model in cross-validation. For example, for intensity ratings of exaltolide at a high dilution, the linear model predicts 4.9% of variation in phenotype, compared to 16% predicted by the RF model. Additionally, the RF model predicted several novel OR interactions that may alter perception that we can test using our cell-based receptor assay. Machine learning is a powerful tool for examining multi-gene interactions in genome wide association studies. The olfactory system is ideal for fostering these analyses because the combinatorial code suggests OR interaction, and we can test novel predictions with our established receptor assay.

Small, Portable System For Recording Olfactory-Evoked Potentials
David W Smith1,2, Mark A Hanus3, William D Woolf2, Andreas Keil1,4
1Program in Behavioral and Cognitive Neuroscience, Department of Psychology, University of Florida, Gainesville, FL, United States, 2Olfaxis, LLC, Durham, NC, United States, 3Tucker-Davis Technologies, Alachua, FL, United States, 4Center for the Study of Emotion and Attention, Gaineville, FL, United States

While psychophysical measures of olfactory function still represent the gold standard in assessing olfactory sensitivity in both humans and non-human animals, behavioral measures are time consuming and data can only be obtained from subjects who understand and follow instructions.  An alternative approach is using electrophysiological recordings, specifically olfactory evoked potentials (OEPs). Measurement of evoked potentials, however, has traditionally required complex instrumentation that produces an abrupt odorant onset yet, critically, no changes in overall air pressure that can produce myogenic and somatosensory artifacts.  Here we describe use of a new, portable odorant generation (OGM; Olfaxis, LLC, Durham, NC) and electrophysiological recording system (LabRAT; Tucker-Davis Technologies, Alachua, FL). We recorded olfactory evoked potentials in 25 human subjects (3 female, 21-34 years).  Neural responses generated by 20 800 ms birhinal odor pulses (6 lpm flow rate, 10-ms IPI; odor onset time constant <10 ms) were recorded from surface electrodes placed at the sellion, between the midline and medial canthus, and trial-averaged.  OEP waveforms were observed as negative deflections of 2-10 µV, with response latencies of ~80-100 ms; differences in waveform amplitude and morphology suggest differences in odor sensitivity.  Significant inter-rhinal response differences were evident in subjects reporting inter-nostril differences in odor sensitivity prior to testing. This system can be used with either humans or non-human animals

Optopharmacology Of Odorants: Photoactivatable Ligands For Chemosensory Research
Kirill Ukhanov1,2, Sangram Gore4, Cyril Herbivo4, Naeem Asad4, Yuriy Bobkov2,3, Jeffrey R Martens1,2, Timothy R Dore4
1University of Florida, Gainesville, FL, United States, 2New York University Abu Dhabi, Abu Dhabi, *, United Arab Emirates, 3New York University Abu Dhabi, Abu Dhabi, *, United Arab Emirates, 4New York University Abu Dhabi, Abu Dhabi, *, United Arab Emirates, 5University of Florida, St.Augustine, FL, United States, 6University of Florida, Gainesville, FL, United States, 7New York University Abu Dhabi, Abu Dhabi, *, United Arab Emirates

The chemosensory system of any animal relies on a vast array of detectors tuned to distinct chemical cues. Odorant receptors and the ion channels of the TRP family are all uniquely expressed in a species-specific manner. Great effort has been made to characterize the molecular and pharmacological identity of these proteins. Nevertheless, most of the natural ligands are highly hydrophobic molecules preventing controlled delivery. We sought to develop photoprotected, biologically inactive odorants that could be delivered to the target receptor or ion channel and effectively activated by a short light pulse. Eugenol, benzaldehyde, 2-phenyl ethylamine, butanethiol, and ethanethiol were modified by covalently attaching the photoremovable protecting group (8-cyano-7-hydroxyquinolin-2-yl)methyl (CyHQ). CyHQ derivatives were characterized in vitro and shown to release the active odorant upon illumination with 365-nm light. We characterized their bioactivity by measuring the electroolfactogram (EOG) from mouse olfactory epithelium. Activation was dependent on light pulse duration and intensity. The kinetics of the light-activated response was compared with a the EOG evoked by a pulse of vaporized amyl acetate. In addition, we tested the applicability of the approach to activate TRPA1 and TRPV1 ion channels heterologously expressed in HEK293 cells. The photorelease of eugenol and both thiol compounds perfusing the HEK293-TRPA1 cells robustly activated inward ion currents within milliseconds of the light pulse. Photoactivation of TRPA1 channels was far superior to activation by conventional bath application of the ligands. Illumination with 405 nm light was also sufficient to activate TRPV1 channels. We conclude that photoprotected odorants can be successfully implemented in chemosensory research.

Antiviral Function Of Type I And Type Iii Interferons In The Olfactory Epithelium And Olfactory Bulb
Ahmad Zedan1, Ashley D. Winters1, Ashley Takeshita1, Shuangyan Wang2, Qizhi Gong1
1University of California, Davis, CA, United States, 2Qingdao University, Qingdao, *, China

The olfactory epithelium (OE) is one of the few sites where environmental pathogens can gain direct access to the brain. Despite this vulnerable arrangement, little is known about the protective mechanisms in place to prevent viral infection and entry into the brain. We systematically investigated innate immune responses in the olfactory mucosa upon exposure to vesicular stomatitis virus (VSV) by RNA-seq. Among many transcriptionally regulated cytokines and chemokines, interferon (ifn) responses were observed. Type I (a and b) and type III (l) ifns are known antiviral cytokines in the respiratory epithelium. Their function and mechanism of action in the OE is unknown. We observed a robust upregulation of ifn α2, α4, β1 and λ2/3  transcript levels compared to PBS instillation control at 24hr post nasal VSV instillation (hrPI), while both ifna and ifnl receptor levels stay constant at both 24 and 48 hrPI. Activation of ifn signaling, indicated by the presence of pStat1 and pStat2, is detected in the OE by western blotting. Ifn stimulated genes (ISGs): ifit2, ifit3, oas1 and Irf7 were also transcriptionally upregulated at these time points. To determine ifn’s antiviral function, we provided exogenous ifnl before VSV instillation. The presence of ifnl significantly reduced the VSV viral load compared to PBS controls both in the OE and olfactory bulb (OB). Individual knockout of ifnar1 and ifnlr1 does not appear to change the transcript levels of ISGs and viral load in the OE at 24hrs. We hypothesize that a combined type I and III ifn signaling are likely required to inhibit viral proliferation in the olfactory system. 

Trpm4 Selectively Interacts With L-Type Voltage Gated Calcium Channels (Vgccs) In Type Iii Taste Receptor Cells
Debarghya Dutta Banik, Kathryn F. Medler
University at Buffalo, Buffalo, NY, United States

There are functionally distinct populations of taste receptor cells (TRCs) that use different signaling pathways to transduce taste stimuli to the brain. Type II TRCs transduce bitter, sweet, and umami taste stimuli through the activation of a GPCR pathway. These cells lack conventional synapses and do not express VGCCs. Type III TRCs have conventional synapses, express VGCCs and detect salty and sour stimuli. We recently reported that TRPM4 is expressed in TRCs. Like TRPM5, TRPM4 is a monovalent selective voltage modulated TRP channel that is activated by intracellular calcium. In Type II TRCs, TRPM4 contributes to taste evoked sodium signaling like TRPM5. Loss of either TRPM4 or TRPM5 significantly impairs taste, and loss of both completely abolishes the ability to detect bitter, sweet, and umami stimuli. We also reported that TRPM4 is expressed in Type III TRCs, but its function in these cells is still unknown. In this study we used live cell imaging, KO mice and pharmacological inhibitors to define the role of TRPM4 in Type III TRCs. We found that TRPM4 affects the membrane potential and selectively regulates the activity of L-type VGCCs in Type III TRCs. In Type II TRCs, we also found that TRPM4 affects the taste evoked calcium release signal, while TRPM5 does not. Our findings demonstrate that TRPM4 is a key regulator of calcium signaling in TRCs, but its functions vary by cell types.  In Type II TRCs, TRPM4 regulates the calcium release signal, while in Type III TRCs it regulates the calcium influx signal.

Common Bitter Stimuli Show Differences In Their Temporal Profiles Before And After Swallowing
Molly J. Higgins1,2, John E. Hayes1,2
1Sensory Evaluation Center, University Park, PA, United States, 2Department of Food Science, University Park, PA, United States

Prior work suggests individuals can distinguish between bitter stimuli that are nominally matched for intensity: potential cues for this discrimination may include regional or temporal differences. Here, classical time intensity methods were used to assess ten bitterants dissolved in water: caffeine, quinine, l-phenylalanine, l-tryptophan, urea, naringin, SOA (sucrose octaacetate), and 3 distinct hop extracts. Trained assessors (n=14) rated the overall intensity of each bitterant continuously for 90 sec, in triplicate. During tasting, solutions were swished in the mouth for 10 seconds and then swallowed. Smoothed mean curves were generated from the triplicate ratings from each assessor for each bitterant. Using these curves, scaffolding parameters were calculated: max intensity, time to max intensity (Tmax), and area under the curve (AUC) before and after swallowing. For each parameter, mixed model ANOVA was used to test for differences between bitterants. Significant differences were observed for maximum intensity, Tmax, AUC before and after swallowing, and intensity at 90 seconds. Tmax was significantly shorter for the amino acids, urea, and quinine. Also, visual inspection of the temporal curves suggests intensity of some bitterants (urea, naringin, hop extracts) increased substantially after swallowing while the intensity of other bitterants (amino acids, caffeine, quinine) did not change or increased only slightly after swallowing. Present data indicate common bitter stimuli found in the food supply show substantial differences in their temporal profiles. Additional work is needed to determine whether these temporal properties may be systematically related to differential liking and/or intake of bitter food products.

Molecular Elements Of The Osmotic Taste Cell Response
Angela S. Mohrman 1,2, Timothy A. Gilbertson 2
1University of Central Florida, Burnett School of Biomedical Sciences, Orlando , FL, United States, 2University of Central Florida, College of Medicine Internal Medicine, Orlando , FL, United States

Recently, the chemosensitivity of the taste system has been expanded to include a number of compounds, including water, that do not fit neatly into the traditional 5 classes of taste stimuli.  We have shown that water, for example, activates rodent taste cells apparently via permeation through aquaporin (AQP) channels, an increase in cell volume and eventually an electrophysiological response via opening of swelling-activated Cl- channels. Specific molecular components in this pathway remain largely unknown, but it appears to be similar to hypoosmotic responses found in a variety of transporting epithelia (Danziger & Zeidel, Clin J Am Soc Nephrol 10:852, 2015). The goal of the current study is to revisit osmotic sensing (water taste) in a mouse model to identify and functional characterize the molecular elements underlying the ability of taste cells to respond to hypoosmotic stimuli. We have used quantitative real time PCR to identify the expression of some of the suspected components that may contribute to water detection. We have found that murine taste cells express AQP2, AQP5, chloride channel 2 and volume-regulated anion channel subunit LRRC8a. We are currently working to determine the subtype(s) of taste cells that express these components. Isolated taste cells show increases in intracellular Ca2+ during application of hypoosmotic stimuli in Ca2+ imaging assays. This response of taste cells to the osmotic environment argues that the taste system is sensitive to the overall nature of the stimulus environment, a phenomenon that is reflected altered responsiveness to sweet and fatty acid tastants presented in varying osmotic conditions. Together, our data argue the taste system is sensitive to hypoosmolarity, which may influence both tastant responses and be reflective of true water taste.

Overproduction Of Type Iii Cells In Skn1A Knockout Mice Does Not Change The Number Of Geniculate Ganglion Neurons Expressing The Serotonin Receptor 5-Ht3A
Aurelie Vandenbeuch, Eric Larson, Sue Kinnamon
Department of Otolaryngology, University of Colorado, School of Medicine, Aurora, CO, United States

The Skn-1a transcription factor is required for the development of Type II taste receptor cells in taste buds. Knockout of this transcription factor eliminates the ability of mice to taste sweet, bitter, and umami substances while preserving sour taste. Skn-1a knockout mice have an increased number of Type III taste receptor cells, which release serotonin (5-HT) in response to sour stimulation. Despite the more numerous Type III cells, gustatory nerve responses to sour substances are equivalent to those in wildtype animals, raising the hypothesis that the number of nerve fibers contacting Type III cells remains unchanged. Indeed, a recent report using retrograde transfer of wheat-germ agglutinin (WGA) from Type III cells concluded that knockout of Skn-1a has no effect on the number of geniculate and nodose/petrosal ganglion cells whose peripheral fibers contact Type III cells (Maeda et al., 2017). In the present study, we expand on these findings. First, we confirm the findings of Maeda et al. using an alternate approach. We have previously shown that serotonin receptor 3A (5-HT3A) containing nerve fibers preferentially target Type III taste receptor cells. When the 5-HT3A-GFP reporter mouse is crossed with the Skn-1a knockout mice, we find no change in the number of 5-HT3A-expressing geniculate ganglion neurons, despite increased numbers of Type III taste receptor cells. Secondly, single-cell physiology shows that only 5-HT3A-expressing geniculate ganglion neurons respond to exogenous 5-HT, and that most ganglion neurons respond to ATP, similar to observations in wildtype mice. These findings raise many follow-up questions pertaining to the innervation of the additional Type III taste receptor cells, and the role of ATP signaling in the absence of Type II taste receptor cells.

Bitter Taste Receptor T2R7 And Umami Taste Receptor Subunit T1R1 Are Expressed Largely In Vimentin-Negative Taste Bud Cells Of Chickens
Yuta Yoshida1,2, Zhonghou Wang1, Kayvan F. Tehrani1, Emily G. Pendleton1, Ryota Tanaka2, Luke J. Mortensen1, Shotaro Nishimura2, Shoji Tabata2, Hong-Xiang Liu1, Fuminori Kawabata3
1University of Georgia, Athens, GA, United States, 2Kyushu University, Fukuoka, *, Japan, 3Hirosaki University, Hirosaki, *, Japan

In the mammalian taste system, bitter taste is sensed by the taste receptor type 2 (T2R) family, and sweet and umami tastes are sensed by the heterodimer of the taste receptor type 1 (T1R) family. In the chicken genome, 3 T2R genes (T2R1, T2R2, and T2R7) and 2 T1R genes for the umami taste receptor (T1R1 and T1R3) have been detected. However, the distribution of these receptor proteins in the taste buds of chickens has not been elucidated. Here, we detected the localization of bitter taste receptor T2R7 and umami taste receptor subunit T1R1 in chicken taste buds, using a molecular marker for chicken taste buds, Vimentin. T2R7 and T1R1 were expressed in the taste bud clusters on the oral epithelial sheets of chickens, and among all three regions of gustatory tissues of chickens, the palate, base of the oral cavity, and the posterior tongue. The similar distribution patterns and numbers between taste bud clusters expressing these receptors and those expressing Vimentin on the oral epithelial sheets of chickens suggested that T2R7 and T1R1 were expressed in most of the taste bud clusters in chickens. Interestingly, T2R7 and T1R1 were hardly merged with Vimentin at the taste bud cell level, and 3-D image analyses clearly revealed that these receptors were expressed largely in Vimentin-negative taste bud cells. These results suggested that the taste bud cell populations, labeled by different markers, e.g., T2R7, T1R1, and Vimentin, may serve distinct functions in taste perception. Taken together, the present results suggested that chickens possess fundamental bitter and umami sensing mechanisms in the taste buds, and the mechanisms were broadly present in the oral cavity of chickens.

Tuesday, April 16, 2019

7:30 - 9:00 AMEstero Foyer

8:00 - 10:00 AMEstero Ballroom
Poster Session III

A Tastier Mouth: New Taste Structure In The Oral Cavity.
Grace E. Beck1,2, Quan T. Nguyen1, Marco Tizzano1,2
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2University of Pennsylvania School of Dental Medicine, Philadelphia, PA, United States

Taste in the gustatory system allows to distinguish between safe and harmful food, and to gauge the nutritional value of food. Digestive enzymes in saliva begin to dissolve food into base chemicals that are detected by taste buds (TBs) containing three different cell types involved in the perception of the five basic tastes. Von Ebner's glands, found adjacent to the moats surrounding the circumvallate and foliate papillae, are exocrine salivary glands that secrete digestive enzymes and presumably flush material out of the papillae. Recently, we discovered a new chemosensory structure in the mouse oral cavity consisting of unorganized TBs not contained within troughs associated with ducts and a gland at the rear of the mandible, distal to the last molar and anterior to the ascending ramus. Similar to the circumvallate and foliate papillae, the retromolar chemosensory structure contains TBs surrounding the orifice of ducts originating from a salivary gland. The retromolar gland is morphologically similar to the Von Ebner's glands, and is located below the mucosa of the retromolar gap extending posteriorly in the retromolar trigone. Above the gland and ducts, TBs are positioned on the surface of the retromolar epithelium, surrounding the duct orifices. Using immunohistochemistry and RT-PCR, we determined that these TBs have chemosensory features expressing many canonical taste signaling elements. The composition of the gland secretions is unknown. Interestingly, third molar extraction in humans has reportedly led to taste changes, possibly due to the procedure disrupting the retromolar tissue. Further studies are needed to determine if this structure plays any role in gustatory perception and if the retromolar TBs are potentially new pharmacological targets for taste or dry mouth disturbances.

Glomerular Signals During Unrestrained Olfactory Search In Mice
Teresa Findley1, Ian Jackson1,2, Morgan Brown1, Blake Holcomb1, Nelly Nouboussi1, Roman Shusterman1, Jared Acosta-King1, David Wyrick1, Bishara Korkor1, Yashar Ahmadian1, Matt Smear1
1University of Oregon, Eugene, OR, United States, 2Reed College, Portland, OR, United States

The olfactory system plays a principal role in search behaviors for many animals. However, the underlying computations of such search behaviors, especially under naturally turbulent conditions, are largely unknown. To investigate the behavioral structure of olfactory search in such turbulent conditions, our lab developed a behavioral assay for unrestrained mice. With this assay, we demonstrated that mice can reliably search up an odor concentration gradient that contains noise due to turbulence. Further, we found that mice develop sampling strategies for search involving head movement and fast sniffing. In order to understand the computational basis of these behaviors, we now strive to compare these sampling movements directly against sensory input during our search task. However, the unpredictability of air turbulence and the limitations of chemical sensor technology prevent accurate mapping of the olfactory scene. To overcome this challenge, we have developed a system that uses fiber photometry imaging of olfactory sensory neuron terminals in the glomerular layer of the olfactory bulb. Thus, we can capture activity at the first layer of sensory input to the brain in freely-moving mice. Using this technique, we not only overcome the challenge of detecting local odor concentration at the nose but incorporate perturbations from local turbulence, whisking, and sniffing. Our new behavioral assay accommodates fiber photometry recordings, electrophysiological recordings, and optogenetic manipulations. Measuring and manipulating sensory input during unrestrained olfactory search will offer novel insights into olfactory circuits and behavior.

Mapping Chemoreceptors In The Human Olfactory System
Lulu Korsak1, Sarah Kwon1, Olga Lacki1,2, Sarah Kaye3, Thomas Bozza3, Jay Gottfried1
1University of Pennsylvania, Philadelphia, PA, United States, 2Jagiellonian University, Krakow, *, Poland, 3Northwestern University, Evanston, IL, United States

Our current understanding of the molecular organization of the human olfactory system is largely based on extrapolations of studies in model organisms. Fundamental principles such as the expression of a single chemoreceptor per neuron, zonal chemoreceptor expression in the olfactory epithelium, and convergence of axons expressing the same chemoreceptor into a small number of discreet glomeruli in the olfactory bulb have all been elucidated with specialized tools such as genetically modified mice and validated chemoreceptor-specific antibodies. To date, these tools had not been available for studying human tissue. We have generated antibodies to human odorant receptors (ORs) and trace amine-associated receptors (TAARs), and have validated the antibodies using gene-targeted mouse lines that express human receptors. The antibodies are being used to visualize receptor expression in human olfactory epithelium and bulb. The three receptors examined exhibited punctate expression in human sensory neurons, with no apparent zonal organization across the epithelium. Strikingly, one of the OR antibodies labeled many glomeruli throughout the olfactory bulb, in contrast to the strict convergence observed in mice. Our approach provides an unprecedented resource to uncover the organization of the human olfactory system, and our observations raise questions about the requirement of strict glomerular convergence in human olfactory information processing.

Taste Neurons Vary In Degree Of Converging Input From Taste Receptor Cells.
Lisa Ohman-Gault, Tao Huang, Zachary Whiddon, Robin F. Krimm
Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY, United States

Individual taste neurons show tremendous variation in peripheral morphology. The next step is to determine whether these morphological variations dictate variation in peripheral connectivity to taste receptor cells (TRCs). Using a whole mount immunohistochemistry to stain taste buds combined with sparse cell genetic labeling of individual chorda tympani neurons, we analyzed the proximity of individual chorda tympani nerve fibers to TRCs using the Imaris software. We examined 77 separate fiber branches entering the taste bud, of these 52% contact (come within a distance below the resolution of the light microscope) one taste receptor cell (mean = 1.4, range= 0-4) whereas 36% contact more than one and 12% form no contacts. Of the fibers contacting TRCs, 87% of fibers contact TRCs of the same type and 13% contact TRCs of multiple types. Some fibers follow along a taste receptor cell for a considerable distance (13mm, long contacts), while others do not (short contacts, 3µm). Contacts are formed by all branch order types (1st-7th order) but most frequently with 3rd order branches. Next, we traced whole neurons from the base of the tongue. Some neurons (37.5%) innervate only one taste bud, branch sparsely (3-5 branch ends), and make 1-5 contacts with 1-2 taste receptor cells of the same type. Other neurons (62.5%) branch more robustly to innervate 3-5 taste buds, with 13-27 branch ends, making 7-14 contacts with 4-13 taste receptor cells of both types. The total length of the neuron in the taste bud predicts the number of contacts made with taste receptor cells (r = 0.92). We suggest that sparsely branched neurons contacting only a few TRCs of the same type may be narrowly tuned, whereas neurons that branch robustly to innervate many taste receptor cells of different kinds may be broadly-tuned. 

Real-Time Measurement Of Olfactory Information Using Head-Mounted Sensors During Odor-Guided Navigation
Mohammad F Tariq1, Aliena Lowell1, Suzanne M Lewis1, David Perkel2, David Gire1
1Dept. of Psychology, University of Washington, Seattle, WA, United States, 2Dept. of Biology & Otolaryngology, University of Washington, Seattle, WA, United States

Olfaction is one of the key sensory modalities that allows animals to navigate their environment in search of food, mates, and shelter as well as to avoid predation. The spread of odor molecules over large distances is governed by the turbulent movement of fluids. This results in intermittent and spatiotemporally varying contact between the odor molecules and the searcher. Hence, the olfactory information available to an animal engaged in odor-guided navigation is not uniform but dynamically varies. This creates challenges for correlating odor input with neural processing and decision-making in freely moving animals. We present a robust method for real time monitoring of olfactory information in freely moving mice by using low-cost, light weight sensors that detect common solvent molecules like alcohols. Our results show that these sensors are highly sensitive to low concentrations of ethanol and can follow frequencies of fluctuations up to 12Hz. For our behavioral paradigm, we train mice to associate ethanol with a reward.  They are then tasked to navigate to the location of an ethanol source in a large, custom-made arena designed to produce dynamic odor plumes. Combining the sensor recordings with behavioral tracking of animals’ trajectories will allow us to determine how intermittent odor contacts guide decision-making in animals engaged in odor-guided navigation.

Distribution Of Chorda Tympani Nerve Fibers In The Fungiform Papilla That Respond To Lingual Touch And Cold Stimuli Demonstrated With Hedgehog Pathway Inhibitor Sonidegib Drug Treatment
Archana Kumari, Libo Li, Christopher R Donnelly, Brian A Pierchala, Robert M. Bradley, Charlotte M. Mistretta
Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, United States

The chorda tympani (CT) fibers from neurons in the geniculate ganglion project into and around taste buds (TB) in fungiform papillae (FP) and respond to chemical, touch and cold lingual stimulation. Thus the multimodal CT innervates receptors and/or includes endings that are chemosensory and somatosensory in nature. If rodents are treated with a Hedgehog pathway inhibitor (HPI) drug, Sonidegib, used in cancer patients, the TB and neurophysiological responses from the CT nerve to lingual chemical stimulation are eliminated. Strikingly, responses to lingual stroking and cold water stimuli remain. To identify CT nerve distributions and endings that respond to somatosensory stimuli, in the absence of TB and chemosensation, we used Phox2bCre;Tdtomato/+ mice that have labeled CT fibers. Mice were gavaged with Sonidgeib (TB eliminated) or Vehicle for 28 days and CT distributions determined. Phox2b+ fibers in Vehicle-treated FP were in a compact trajectory directly to the TB, with fewer extragemmal fibers in the FP epithelial apex. With Sonidegib treatment the Phox2b+ fibers extended more widely across the FP at the epithelial/stromal interface; the fibers did not extend into the former TB-bearing epithelium but were extensive in the extragemmal FP region. Dual labeling was conducted with antibodies to P2X3, NF-H, K8, tyrosine hydroxylase (TH), GAP43 or S100B. TH+, GAP43+ and S100B+ fibers partially overlapped with Phox2b+ fibers, in and external to TB, but also distributed more extensively throughout the FP epithelium and stroma. We propose that the expanded Phox2b-labeled fibers seen with the HPI drug, Sonidegib, incorporate CT somatosensory-responding and disorganized chemosensory elements. The analysis yields data about the nature and location of CT fibers that respond to touch and cold stimuli.

Sox2 In The Oral Epithelial Stem Cells Is Necessary For The Differentiation To Taste Bud Cells
Makoto Ohmoto1,2, Ichiro Matsumoto1
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2Center for Biological Resources and Informatics, Tokyo Institute of Technology, Yokohama, *, Japan

Oral epithelial cells including taste bud cells and non-gustatory epithelial cells arise from local epithelial stem cells and are maintained through continuous turnover. Stem cells in the oral epithelium are located at the base of epithelial layer and express Sox2. We induced Sox2 deletion only in the Krt5-expressing cells such as oral epithelial stem cells using the Krt5-CreERT2 knockin strain and studied the roles of Sox2 in the oral epithelial stem cells. After the deletion of Sox2 by tamoxifen injection, the number of taste bud cells decreased over time, and all taste bud cells were lost by 2 weeks. In the mice in which tdTomato expression was induced concomitantly with the deletion of Sox2 in the oral epithelial stem cells, fluorescence of tdTomato was observed in the non-gustatory epithelial cells but not in the taste buds after tamoxifen injection, suggesting that no new taste bud cells were supplied from Sox2-deficient stem cells. These results indicate that Sox2 in the oral epithelial stem cells is necessary for the differentiation to taste bud cells.

Advillin Genetically Identifies A Subset Of Taste Neurons And Type Ii Receptor Cells
Jennifer Xu1, Robin F. Krimm2
1dupont Manual High School, Louisville, KY, United States, 2Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY, United States

Advillin-Cre gene recombination is commonly used within the somatosensory field to target and isolate peripheral sensory neurons for both identification and gene manipulation. It has also been used in the taste system, but lack of characterization makes it unclear which cells are influenced by Cre mediated recombination. This project utilizes an Advillin-Cre mouse model to characterize Advillin-Cre expression in taste receptor cells and geniculate ganglion neurons. Using a standard immunohistochemistry procedure with antibodies labeling for dsRed in Advillin-Cre:tdTomato mice, we found that approximately 74% to 95% of taste buds contained Advillin-Cre positive innervation (n=2 mice; 40 taste buds/mouse). All taste buds analyzed had Advillin expression within some taste receptor cells. Whole-mount analysis in Advillin-Cre:tdTomato mice, co-labeled with PLCβ2 and Car4 revealed that 62±6% of PLCβ2+ taste receptor cells were Advillin-positive (n=2 mice; 80 taste buds/mice). Car4+ receptor cells lacked Advillin. Chorda tympani nerve labeling in Advillin-Cre:tdTomato mice revealed that one-third of neurons innervating the tongue underwent gene recombination (n=5). We are currently tracing Advillin-positive fibers that enter the taste bud to determine if they have a unique morphology or if they come in contact with a specific receptor cell type.  Preliminary data indicate that Advillin-positive fibers come in contact with both Car4-positive and PLCβ2-positive taste receptor cells. In conclusion, Advillin-Cre expression defines a subtype of PLCβ2 taste receptor cells and a subset of taste neurons. Therefore, this animal is useful tool for gene recombination in both receptor cells and neuronal subpopulations, but can not be used to remove genes in all cells of either population.

A Small Subset Of Type Iii Taste Cells Show Both Atypical Mitochondria And Conventional Synapses Onto Nerve Processes In Mouse Circumvallate Taste Buds
Ruibiao Yang, Robert S. Lasher, Ernesto Salcedo, Courtney E. Wilson, Thomas E. Finger
Rocky Mountain Taste & Smell Center, Dept. of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States

Different taste cells maintain different types of functional contact with gustatory nerve fibers. Type II taste cells form unconventional purinergic synapses characterized by atypical mitochondria closely apposed to CALHM1/3 channels in the plasma membrane; Type III taste cells form conventional synapses with synaptic vesicles at points of contact with nerve processes. In the present study using Serial Blockface SEM, we reconstructed the 3D structure of taste cells and their attendant nerve fibers, analyzing the ultrastructure of each point of specialized contact. Type II cells are spindle-shaped with a large circular nucleus, lucent cytoplasm, swollen smooth endoplasmic reticulum, and a single microvillus extending into the taste pore. Nearly all Type II cells display atypical mitochondria at the points of contact nerve fibers. In contrast, Type III cells are more slender, display a nucleus with prominent invaginations and have a single, long, blunt microvillus that extends into the taste pore. Type III cells present conventional synapses from the cells onto nerve processes. However, a small number of taste cells, with Type III cell morphology, exhibit both atypical mitochondria and conventional synapses onto nerve processes. These synapses are characterized by clusters of 40-60 nm clear synaptic vesicles, most of which are closely associated with or directly contacting the presynaptic membrane. The associated atypical mitochondria with tubular cristae lie close to the conventional synaptic sites. These findings suggest that a subset of Type III cells may use two different taste signaling mechanisms. The presence of atypical mitochondria in some Type III cells may underlie the dependence on purinergic signaling for transmission of information from Type III cells to the nerve fibers.  

Studying The Neuronal Substrates Of Internal Models Via A Novel Closed-Loop Olfactory Task For Mice
Priyanka Gupta1, Marie Dussauze1,2, Uri Livneh1, Dinu F Albeanu1,2
1Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, United States, 2Watson School of Biological Sciences, Cold Spring Harbor, NY, United States

During behavior, sensation and action operate in closed-loop. Movements shape sensory input, and sensory inputs guide motor commands. Through experience, the brain learns the reciprocal relationship between sensory inputs and movements to build internal models that predict the sensory consequences of upcoming actions (sensorimotor predictions). Comparing internal sensory predictions to actual sensory observations generates prediction errors that can be minimized by learning increasingly accurate models of the world. This exchange of sensory inputs and egocentric expectations is at the core of active perception. To study internal models both at behavioral and circuit-level, we developed a novel behavioral task where head-fixed mice are trained to steer the left-right location of an odor source by controlling a light-weight lever with their forepaws. In this manner, 1) we link a precise motor action to well-defined sensory expectations (odor location) and 2) subsequently violate the learnt expectations via online feedback perturbations in trained animals. Expert mice (6 out of 6 trained mice, training period <2 weeks, >90% accuracy, 400-800 trials/session) showed precise movements that were locked to the instantaneous odor feedback during normal closed-loop coupling. However, when sensory feedback was transiently interrupted (halting of odor source) or distorted (displacement of odor source or change in movement gain), movements were initially guided by each animal’s learnt internal model and further, quickly adapted (within few sniffs in single-trials) in accordance with the instantaneous sensory error. We are currently probing activity in olfactory and motor cortex and the olfactory striatum to understand the sensorimotor transformations that enable this behavior.

Neural Basis Of Olfactory And Trigeminal Interaction
Lu Jiaming1,2, Krish Sathian3, 4, 5, Qing Yang1, 6, Prasanna Karunanayaka1, 4
1Radiology, Center for NMR Research, Penn State University College of Medicine, Hershey, PA, United States, 2Drum Tower Hospital, Medical School of Nanjing University, Hershey, PA, United States, 3Neurology, Penn State University College of Medicine, Hershey, PA, United States, 4Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, PA, United States, 5Department of Psychology, Penn State University College of Medicine, Hershey, PA, United States, 6Neurosurgery, Penn State University College of Medicine, Hershey, PA, United States

Olfactory sensitivity is influenced by intranasal trigeminal sensation. For instance, sniffing is central to how humans and animals perceive odors. However, the influences of olfactory information on trigeminal perception remain largely unknown. Two recent behavioral studies [Tremblay et al. (2018), Chem Senses(43):611-616 and Karunanayaka et al. (2018), AChems]reported that trigeminal sensitivity was enhanced during co-stimulation with pure and mixed olfactory and trigeminal (bimodal) stimuli. In this functional magnetic resonance imaging (fMRI) study, we investigated the neural basis of trigeminal sensitivity enhancement during olfactory co-stimulation along with intranasal somatosensory stimulation. Twenty-two healthy human subjects, with normal olfactory function, performed a localization task for weak air-puff stimuli in the scanner, in the presence or absence of a pure odorant, phenyl ethyl alcohol (PEA; rose odor). During this task a trigeminal stimulus was presented to one or the other nostril and the subject was required to localize the stimulated nostril. Although PEA alone could not be localized, when accompanied by a weak air-puff in the ipsilateral nostril, localization accuracy significantly improved, relative to presentation of the air-puff without the odorant. The enhancement of localization was absent when the air-puff and PEA were presented to opposite nostril. Our fMRI data revealed that olfactory-trigeminal integration may be mediated by the POC via superadditive interactions. Superadditive effects were also observed in the (i) insula (INS) and (ii) bilateral superior temporal sulcus (STS). These data provide strong functional evidence for integration of olfactory and trigeminal sensory inputs.

High Familiarity And Intensity Accelerate Odor Detection
Tatsu Kobayakawa1, Hiroko Mochizuki-Kawai2, Takefumi Kobayashi3, Naomi Gotow1
1National Institute of Advanced industrial science and technology, Tsukuba, *, Japan, 2Institute of Vegetable and Floriculture Science, National Agriculture and Food Research Organization, Tsukuba, *, Japan, 3Bunkyo University, Department of Human Studies, Saitama, *, Japan

In visual perception, it is known that higher familiarity for a certain stimulus leads quicker detection. Odor perception, however, it is still uncovered the relationship between familiarity for odor stimulus and speed of detection, yet. In this study, we measured simple detection time for four olfactory stimuli, rose, anis, vanilla and mint. Participant took part in four experimental sessions (one session for one odorant), after each session, we asked familiarity, intensity, pleasantness and edibility for each odorant. To measure reaction time properly, we monitored the odor material at the end of tube of the olfactometer (near the nose of subject) by using a high-speed gas sensor. We presented thirty trials in one session, and ISI was approximately forty seconds. We defined high and low familiarity groups for each odorant, and compared reaction time, perceived intensity, pleasantness and edibility, and found significant difference between detection time and perceived intensity. These results suggested familiarity and perceived intensity would affect detection time for odorant.

The Effect Of Presentation Route On Olfaction Perception.
Robert Pellegrino1, Jonas Olofsson2, Thomas Hörberg2, Curtis Luckett1
1University of Tennessee, Knoxville, TN, United States, 2Stockholm University, Stockholm, *, Sweden

The sensitivity to odors and the way we characterize them are two main focuses of peripheral and central processes involved in olfactory functionality. Most olfactory research assess only one route of odor presentation, orthonasal, while ignoring odors perceived within the interior of the body rather than from the external world, or retronsal perception. In a counter-balanced design, ortho- and retronasal olfactory abilities were compared using the SMELL-S threshold test and an odor identification (ID) schema. The ID test measured uncued and cued ID responses to 8 food and 8 non-food odors ranging in valance. Olfactory association index (OAI, how strong a word is associated with olfaction) and olfactory specificity index (OSI, how specific a word is in its description to odor) were calculated on descriptive terms given for uncued ID responses. Lower sensitivities for the retronasal olfactory pathway were observed compared to orthonasal. While internally perceived odors were characterized differently than orthonasal odors although uncued identification frequencies for both were low. This research adds supporting evidence for differences in olfactory sensitives and natural language processing between routes of odor presentation.

Emotional Contagion Based On Intensity Of Anxiety And Expertise Of Recipients: A Case Of Dental Professionals
Preet B. Singh1,2, Amin Homayouni2, Carl W. Glad2, Malene Rusten2, Morten Rykke2, Valentina Parma3,4
1Department of Oral Surgery and Oral Medicine, Institute of Clinical Dentistry, Faculty of Dentistry, University of Oslo, , Oslo, *, Norway, 2Department of Restorative Dentistry, Institute of Clinical Dentistry, Faculty of Dentistry, University of Oslo,, Oslo, *, Norway, 3William James Center for Research,Rua Jardim do Tobaco, 34, 1149-041, Lisboa, *, Portugal, 4 Department of Clinical Neuroscience, Karolinska Institutet, Nobels väg 9, 17177, Stockholm, *, Sweden

In the visual modality, the intensity of an emotion induces stronger emotional contagion (EC) in the recipients, and experts tend to show reduced emotional contagion in emotions related to their area of expertise. EC also characterizes human body odor (BO) communication, however it is unclear whether and how the intensity of the emotions presented and the expertise of recipients modulate the subjective, behavioral and biological responses to BOs. We previously demonstrated that dental students operating on simulation units felt more stressed and performed a dental task poorly when exposed to BO of anxiety. Here, we tested 43 (37F) students (Age: 23.4  3.7) and 4 (3F) professionals (Age: 37.3  5.2) performing dental task when exposed to BOs collected in low, moderate and high levels of stress. Bayesian analyses on the subjective reports on stress levels reveal that EC between donors and recipients existed only when the anxiety BO was moderate, but not in the low and high stress condition. No reduction in the EC is revealed for professionals. There is sufficient evidence to conclude that the olfactory ratings of intensity, pleasantness and anxiety do not reveal perceptual differences across the low, moderate and high anxiety BOs. However, EC was evident at the level of salivary cortisol in all three levels of anxiety. Dentists performed better than the students, as expected. For them, the best performance occurred when they were exposed to the moderate anxiety BO, as predicted by the Yerkes-Dodson Law. For the students, instead, the performance improved linearly with the increased anxiety in the BO. These findings provide the first evaluation of the role of emotion intensity and experise on the EC evoked by BOs in the context of ecological tasks.

Anticipation Induces A Phase Shift Of Low Frequency Oscillations In Human Piriform Cortex
Ghazaleh Arabkheradmand1, Guangyu Zhou1, Heidi Jiang1, Jay A Gottfried2, Joshua Rosenow1, Jessica Templer1, Gregory Lane1, Christina Zelano1
1Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States, 2Department of Neurology, University of Pennsylvania, Philadelphia, PA, United States

Sensory attention most commonly involves anticipation, which occurs prior to the arrival of a stimulus. Anticipatory states prime the brain for the coming perceptual task. Despite that fact that understanding of the neural signatures of anticipatory states is critical for understanding attention, most research on attention has focused on neural responses, which occur after the arrival of a stimulus. Thus, neural mechanisms underlying anticipatory states are not well understood. In this study, we used intracranial EEG recordings in human subjects performing an olfactory attention task to study anticipatory attention in the human brain.We investigated the spectrotemporal properties of attentional neural signatures during the time prior to stimulus delivery in both attended and unattended conditions. We found that anticipation of olfactory stimuli evokes low frequency (0-2Hz) phase coherence in human piriform cortex. This pre-stimulus phase coherence is correlates with both post-stimulus duration of inhale and post-stimulus odor-induced response magnitudes in piriform cortex. These correlations suggest that anticipatory states effect both odor sampling behavior and odor coding. Together these findings suggest that human piriform cortex carries essential attentional neural signatures prior to any physical contact with the stimuli. 

Interoceptive Accuracy And Its Relation To Insular Activity Following Olfactory Stimulation
Carina Köppel1, Paul Ruser1, Hagen Kitzler2, Thomas Hummel3, Ilona Croy1
1Clinic for psychotherapy and psychosomatic medicine, University Hospital Carl Gustav Carus, Dresden, *, Germany, 2Institute of Diagnostic and Interventional Neuroradiology, University Hospital Carl Gustav Carus, Dresden, *, Germany, 3Smell & Taste Lab, University Hospital Carl Gustav Carus, Dresden, *, Germany

BACKGROUND Also known as the secondary olfactory cortex, the insula plays a key role in the integration of multimodal information. Especially the convergence of internal and external stimuli is crucial for the subjective feeling of “self”. In this context the question arises how intero- and exteroceptive olfactory abilities are related and if this relation is based on insular functioning. METHODS 31 healthy individuals (19 women, 12 men, mean 24,2 years ± 3,65 SD) took part in an experimental setup, consisting of 1) a pretesting of interoceptive accuracy and olfactory function 2) fMRI measurements focusing on the insular activation following olfactory stimulation. RESULTS Olfactory stimulation led to the expected insular activation. Enhanced neuronal engagement in the bilateral insula was observed among participants with high interoceptive accuracy. This neuronal engagement was located in insular subdivisions reported as involved in interoceptive processing. Linear regression analysis of the pretestings revealed a significant coherence between olfactory function and interoceptive accuracy (R²=0.27) CONCLUSION Our results suggest that olfactory stimulation triggers interoceptive functioning. This may lead to an increased processing of internal cues in participants with high interoceptive accuracy. So far, these conclusions are limited to olfactory stimulation and interoceptive accuracy. Further research focusing on the relation of different exteroceptive modalities (e.g. gustation) and interoceptive dimensions is warranted for a future comprehensive interpretation. For now, we suggest a positive relation of interoceptive and exteroceptive abilities based on the common main processing region, the insula cortex.

Portable Odorant Generation And Physiological Recording System To Measure Cortical Olfactory Event-Related Potentials Using Quantitative Electroencephalography
David W Smith1,2, Mark A Hanus3, W David Woolf2, Andreas Keil1,4
1Program in Behavioral and Cognitive Neuroscience, Dept. of Psychology, University of Florida, Gainesville, FL, United States, 2Olfaxis, LLC, Durham, NC, United States, 3Tucker-Davis Technology, Alachua, FL, United States, 4Center for the Study of Emotion and Attention, University of Florida, Gainesville, FL, United States

There is a growing awareness of the central importance of olfaction to quality of life.  Moreover, changes in olfactory function may serve as biomarkers for a wide range of neurologic conditions, ranging from Alzheimer’s and Parkinson’s diseases to mild traumatic brain injury.   Olfactory assessment has most typically taken the form of behavioral measures (e.g., scratch and sniff tests or with laboratory olfactometers).  Here we describe use of a new, portable system for measuring olfactory event-related potentials (oERPs) using quantitative electroencephalography (qEEG) in humans.  The device combines an odor generator (OGM, Olfaxis, LLC, Durham, NC) and neurophysiological recording system (LabRAT, Tucker-Davis Technologies, Alachua, FL).  Neural responses generated by 800-ms birhinal odor pulses (6 lpm flow rate; phenyl ethanol or cosmetic cinnamon; 10-ms interpulse interval; pulse onset time constant of <10 ms) were recorded from 16 EEG electrodes and trial-averaged.  Analysis of EEG waveforms was carried out using MatLAB software (EEGLab toolbox and custom code).  Topographic voltage maps demonstrate activation in olfactory epithelium, though asymmetric in subjects reporting nasal complaints, within 100 ms of odorant initiation and persisting throughout odorant delivery.  A spatio-temporal shift of increased activity was observed from fronto-central to parietal electrode locations.  There was also a significant decrease in alpha band power, centered in the frontal cortex, during odorant presentation.  This system in also suitable for use with non-human animals.

Functionally Distinct Populations Of Gc Neurons Represent Different Properties Of Odor-Taste Mixtures.
Sanaya K. Stocke, Chad L. Samuelsen
University of Louisville, Louisville, KY, United States

The perception of flavor is a multisensory experience requiring the modalities of smell and taste.  Sampling odor-taste mixtures generate robust odor-taste associations. These associations convey that some odor-taste pairs belong together (congruent) and others do not (incongruent). The gustatory cortex (GC) is a site of convergent gustatory and olfactory signals. Functionally distinct populations of neurons in GC represent the different sensory and hedonic (pleasant/unpleasant) properties of individual odors or tastes (Samuelsen and Fontanini, 2017). However, how these distinct populations of neurons represent the properties of congruent and incongruent odor-taste mixtures remains unclear.  To test this, first rats were given repeated experience with two different odor-taste mixtures: one pleasant (isoamyl acetate-sucrose; IA-S) and one unpleasant (benzaldehyde-citric acid; B-CA). Then GC single-unit neural activity was recorded in behaving rats during the intraoral delivery of odors, tastes, and congruent (IA-S & B-CA) and incongruent (IA-CA & B-S) odor-taste mixtures. Our preliminary results suggest that the population of GC neurons that respond to tastes, but not odors represents the gustatory component of odor-taste mixtures, the population that responds to odors, but not tastes represents the congruency of odor-taste mixtures, and the population that responds to both represents the hedonic value of odor-taste mixtures. These preliminary findings suggest that GC neurons are a key component of the network that integrates and processes multimodal chemosensory signals.

Functional Pathways Of Human Primary Olfactory Cortex
Guangyu Zhou, Greg Lane, Christina Zelano
Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States

Human primary olfactory cortex comprises a number of distinct brain structures, including, by definition, all areas that receive direct input from the olfactory bulb. That the olfactory bulb projects directly and simultaneously to a number of distinct cortical brain structures suggests parallel processing across distinct functional pathways in the olfactory system. However, the specific functions and pathways of primary olfactory sub-areas are not well-understood. In this study, we used whole-brain, resting-state functional magnetic resonance imaging, combined with data-driven k-means clustering methods, to parcellate human primary olfactory cortex into sub-regions based on their whole-brain functional connectivity profile, and then characterized the unique functional connectivity profiles of each division. We showed that based on functional connectivity profiles, primary olfactory cortex can be parcellated into four sub-regions that correspond anatomically to the anterior olfactory nucleus, olfactory tubercle, and frontal and temporal piriform cortex. We then showed that primary olfactory sub-regions are functionally connected to distinct sets of brain regions, suggesting dissociable functional pathways. Based on our results, we developed a hypothetical model of the distinct functional pathways of the human olfactory system. Our results provide a potential reference for the functional connectivity networks of primary olfactory cortex, which may provide new insights into the functional role of parallel olfactory processing pathways. 

Proteasomal Regulation Of ∆Np63 In The Horizontal Basal Cells Of The Olfactory Epithelium
Camila M. Barrios-Camacho1,2, Jesse Peterson1, Brian Lin1, James E. Schwob1,2
1Department of Cellular, Molecular, and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University , Boston, MA, United States, 2Program in Neuroscience, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, United States

The sensory neurons of the olfactory epithelium (OE) are vulnerable to injury because of their direct contact with the external environment. To maintain proper olfaction, stem cells in the OE give birth to new neurons throughout life, making the OE a powerful tool to study the mechanisms underlying neural regeneration. One of these stem cell populations — the dormant horizontal basal cells (HBCs) — activate to multipotency and participate in regeneration only after severe injury. The transcription factor ∆Np63 is the molecular switch mediating the transition of HBCs from dormancy to activation. During the injury process, the absolute loss of ∆Np63 protein precedes the absolute loss of ∆Np63 transcript. This discordant relationship suggests that the proteolysis carried out by the ubiquitin-proteasome system modifies and degrades ∆Np63 in response to injury-induced signaling. We treated primary in vitro HBCs with cycloheximide (CHX; a protein synthesis inhibitor) in the presence or absence of proteasomal inhibition with bortezomib (Btz). We found that the half-life of ∆Np63 in CHX-only treated cells is ~4.7 hours in comparison to CHX + Btz-treated cells which showed no change in ∆Np63 levels (n=3; p = 0.015). This suggests that the stability of ∆Np63 expressed in primary in vitro HBCs is mediated by the proteasome. Furthermore, we track the in vivo degradation kinetics of ∆Np63 with FACS and corresponding tissue analysis by completing an acute lesion time-course of CD-1 mice (n=3/time point). Lastly, a combinatorial small molecule approach shows that the levels of ∆Np63 are tunable. Taken together, these findings offer a therapeutic avenue for addressing neurogenic exhaustion in anosmic patients by enhancing the degradation of ∆Np63, thereby activating HBCs and rejuvenating neurogenesis.

The Polycomb Group Protein Cbx8 Is Required For Adult Olfactory Neurogenesis
Rhea Choi1,2, Stefania Goncalves3, Bradley J. Goldstein2,3
1Medical Scientist Training Program, University of Miami, Miami, FL, United States, 2Graduate Program in Neuroscience, University of Miami, Miami, FL, United States, 3Department of Otolaryngology, University of Miami, Miami, FL, United States

Polycomb group genes (PcGs) are a protein family that assemble into multimeric epigenetic complexes, Polycomb repressive complex 1 and 2 (PRC1 and PRC2). Together, PRCs regulate gene expression via histone modifications and chromatin remodeling, controlling cell identity during development or tissue renewal. In the mouse olfactory epithelium, which contains basal stem cells supporting adult neurogenesis, we identified cell type-specific expression of multiple PcGs. Of particular interest, we found that expression of CBX8, a component of PRC1, is restricted to the neuronal lineage. Considering known PRC functions, we hypothesized that CBX8-PRC1 might regulate olfactory neurogenesis by control of lineage-specific transcriptional networks. Our approach combined Cbx8 loss-of-function studies in an in vitro model of adult olfactory neurogenesis, RNA sequencing (RNA-seq) and chromatin studies. Taking advantage of the ability to expand purified neurogenic globose basal cells in culture, we performed chromatin immunoprecipitation with sequencing (ChIP-seq) to identify genome-wide targets of CBX8 and other PcGs. These experiments revealed that Cbx8 depletion led to markedly decreased neurogenesis. Correlating gene expression and ChIP-seq data showed that CBX8-PRC1 can function to activate or repress lineage-specific transcription, for targets such as Ebf genes, Wnt pathway genes, or Pax6.  Our results support a model in which CBX8-PRC1 orchestrates olfactory neurodifferentiation via the regulation of lineage-specific transcriptional networks.

The Early Events Of Horizontal Basal Cell Activation Following Injury
Jonathan D. Louie1,2,4, Daniel B. Herrick1,3,4, Nikolai Schnittke1,3,4, James E. Schwob1
1Department of Developmental, Molecular & Chemical Biology, Tufts University School of Medicine, Boston, MA, United States, 2Program in Neuroscience, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, United States, 3Program in Cell, Molecular & Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, United States, 4Medical Scientist Training Program, Tufts University School of Medicine, Boston, MA, United States

Smell loss can be attributed to aneuronal regions in the aged human olfactory epithelium (OE) that persist due to the continued dormancy of the last remaining resident stem cell population, horizontal basal cells (HBCs). Nonetheless, dormant HBCs (HBCDs) with their enduring presence and capacity to give rise to all OE cell types make them an invaluable asset in reversing age-related hyposmia. Our laboratory has previously demonstrated that HBC status is regulated by the transcription factor, ΔNp63α (p63), in which decreased p63 triggers HBC activation. We have also shown that Notch signaling plays a role in restraining HBCs, which when inhibited leads to aberrant HBC activation. Unfortunately, events that HBCs undergo subsequent to their activation are poorly understood. To address this, we have explored aspects of activated HBC (HBCA) biology that may be critical for them to fully realize their multipotency. Following OE lesion, HBCAs dynamically express the Notch ligand, Dll-1. Additionally, as regeneration progresses and HBCDs reappear, so does the polarity of Notch receptor and ligand expression. These data suggest a continued role for Notch signaling throughout OE regeneration. Furthermore, p63 has been implicated in modulating expression of integrins β1 (Itgb1) and β4 (Itgb4). In accordance, in vitro activation of HBCDs diminishes p63 along with Itgb1 and Itgb4. Surprisingly, findings in vivo suggest that HBCAs may increase Itgb1. These data suggest the potential for Itgb1 post-translational modifications to sustain HBCAs during decreased basal lamina attachment. By interrogating the biology of HBCAs, we hope to elucidate mechanisms that ultimately enable development of hyposmia-reversing therapies.

Strategies For Single-Molecule Tracking Of Sonic Hedgehog Delivery To The Regenerative Niche In Adult Taste Buds
Wan-Jin Lu, Ankit Baghel, Philip A. Beachy
Stanford University, Stanford, CA, United States

We are interested in determining the role of nerve-derived signals in epithelial tissue regeneration, a phenomenon that has been an important topic of inquiry for over one hundred years. Vintschgau and Hönigschmied first proposed in 1877 that the maintenance of taste sensory organs in the tongue depends on innervation from distant ganglion neurons. But conclusive evidence supporting this hypothesis and the underlying mechanism has remained unknown. We previously reported that Sonic hedgehog (Shh), which encodes a secreted protein signal, is expressed in these sensory neurons. Taste receptor cells (TRCs) are lost upon pharmacologic blockade of Hedgehog pathway, accounting for the loss of taste sensation experienced by cancer patients undergoing Hedgehog inhibitor treatment. We also found that TRC regeneration following such pharmacologic ablation requires neuronal expression of Shh and can be substantially enhanced by pharmacologic activation of Hedgehog pathway (Lu et al. PNAS, 2018). To better understand the kinetics and mechanism of neuronally secreted Shh delivery in taste buds, we developed a molecular labeling technique that allow us to trace individual, functionally active Shh molecule in distinct neurons. Our labeling strategies include structure-guided screen to identify positions for insertions for a variety of tags and selecting constructs with the ability to signal as native, newly synthesized Shh. We hope to elucidate the posttranslational processing reactions especially in neurons that result in the formation and cell surface presentation of Shh. Our goal is to develop a new platform to track individual morphogen movements and activity both inside the expressing cell and outside in stem cell microenvironments as they seek and interact with their cognate receptors.

Single Cell Transcriptomics Reveals Rare, Quiescent Gbcs Within The Olfactory Epithelium
Matthew J. Zunitch1,2,3, James E. Schwob3
1Program in Cell, Molecular & Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, United States, 2Medical Scientist Training Program, Tufts University School of Medicine, Boston, MA, United States, 3Department of Developmental, Molecular & Chemical Biology, Tufts University School of Medicine, Boston, MA, United States

The mammalian olfactory epithelium (OE) houses several types of globose basal stem and progenitor cells (GBCs) that enable constitutive and injury-responsive neurogenesis across the lifespan of the organism. Despite usual categorization as the “active” stem cell population of the OE, a label-retaining subtype of GBC (LR-GBC) was discovered in vivo that remains mitotically quiescent for at least 30 days. Beyond this, a comprehensive molecular and functional understanding of LR-GBCs has not been achieved. To address this gap in our understanding we performed deep single-cell mRNA sequencing on 22,000 cells from the mouse olfactory mucosa. We identified large numbers of the expected stem and progenitor cells including canonical globose and horizontal basal cells in addition to other cell types. In addition, our strategy of enriching for constituents of the basal compartment allowed us to identify a stand-alone cluster of cells that to-date have not manifested in OE single cell transcriptomics. These cells, putatively LR-GBCs, co-express the stem cell markers Lgr5 and Sox2 with strikingly high levels of the cell cycle inhibitor p57. Interestingly, LR-GBCs in vivo are devoid of Sox2 protein suggesting post-translational mechanisms may control their activation. Current experiments are addressing how these quiescent cells contribute to post-injury tissue regeneration and whether post-translational control of Sox2 is key for their activation into proliferative multipotent progenitors.  

Prefrontal Cortex Projections To The Olfactory Tubercle
Hillary L. Cansler1,2, Estelle E. in 't Zandt1,2, Daniel W. Wesson1,2
1Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, United States, 2Center for Smell and Taste, University of Florida, Gainesville, FL, United States

Sensory representations in the brain are shaped not only by sensory stimuli themselves, but also by internal states and cognitive factors like attention. In many of our sensory systems, attentional modulation of sensory processing involves top-down inputs from the medial prefrontal cortex (mPFC) to the sensory thalamus, ultimately resulting in enhanced signal-to-noise in the sensory cortex. In the olfactory system, wherein odor information is conveyed directly to the sensory cortex without thalamic processing, the mechanisms underlying attentional modulation of odor processing are unknown. In order to identify candidate pathways involved in selective attention to odors, we performed retrograde tracing experiments to identify neurons projecting into the olfactory tubercle (OT), which exhibits attentional modulation of odor-evoked responses. Rats received unilateral OT injections of a retrograde adeno-associated virus encoding GFP. We identified GFP-expressing neurons in multiple mPFC subregions, including dense populations in primarily layer V of the prelimbic and infralimbic cortices. These results indicate that the prelimbic and infralimbic cortices send direct projections to the OT. The importance of the mPFC for selective attention raises the possibility that this pathway may be a candidate for attentional modulation of odor processing in the OT. Future studies will investigate the involvement of these populations in attentional modulation of odor processing and perception.

Morphological Classification Of Taste Fibers In The Mouse Tongue
Tao Huang, Robin Krimm
University of Louisville, Louisville, KY, United States

The morphological characteristics of peripheral taste neurons is unknown. So we traced 96 taste fibers from the mouse tongue using genetic sparse labeling. We observed tremendous variation in taste neuron complexity, some neurons branch little (a fiber entering a single taste bud with a total of one branch end), while others branch heavily (innervating seven taste buds with 40 total branch ends).  A total of 16 morphological characteristics of the traced fibers were analyzed using K-means clustering analyses, which revealed four categories of the traced fibers: category 1 (44%), category 2 (37%), category 3 (14), and category 4 (5%). Total branch length within taste buds was the single morphological feature that provided the best separation between the categories (p<0.01).  Other measures of branching complexity like the total number of branch ends and the largest branch order were also different across the four categories (p<0.05). The simplest branches (Category 1) were shorter (147±9.8 vs 475±28.9 μm) and innervated fewer taste buds (1.88±0.14 μm), compared to the other three categories (3.81±0.26, p<0.001). The number of separate fibers entering the taste bud predicts differences in total branch length (= 0.75), while the mean branch length within the taste bud does not (= -0.29). If each separate fiber contacts an average of 1.6 taste receptor cells (as EM data suggests), category 1 branches should connect with approximately 4 receptor cells while category 4 fibers would connect with 16 receptor cells. Taken together, the categorization of taste fibers in the tongue suggests increasing convergence across categories, which likely explains differences in degree of tuning.

The Role Of The Medial And Central Subdivisions Of The Human Amygdala In Olfaction
Torben Noto, Guangyu Zhou, Greg Lane, Christina Zelano
Northwestern University, Chicago, IL, United States

The medial and central subdivisions of the human amygdala are part of primary olfactory cortex, in that they receive direct input from the olfactory bulb. However, the role of these areas in olfaction is not well-understood.  The amygdala is critical for processing aversive stimuli and triggering adaptive behaviors in response. In humans, the same areas in the amygdala that receive input from the bulb project directly to respiratory control centers in the brainstem, and directly stimulating these specific subdivisions causes people to halt their nasal breathing. Based on these functional and anatomical properties, we hypothesize that the human amygdala may play a role in mediating fast sniff reduction behaviors in response to aversive odors. Here we use functional neuroimaging combined with respiratory monitoring to measure blood-oxygen-level-dependent (BOLD) activity in the amygdala and brainstem during an olfactory sniffing task. Preliminary data from a single subject suggests that activity in the central amygdala and brainstem is modulated by odor hedonics. Following collection of additional data, we expect to find that olfactory areas of the amygdala and respiratory brainstem areas will show increased connectivity during trials in which adaptive sniffing reductions are present.

Activation Of Gc-D-Positive Necklace Glomeruli Following Olfactory Exposure To Uroguanylin
Dimitri Salzman1,2, Arthur D. Zimmerman1,2, Maria G. Rodriguez1,2, Steven D. Munger1,2
1University of Florida Center for Smell and Taste, Gainesville, FL, United States, 2University of Florida Department of Pharmacology and Therapeutics, Gainesville, FL, United States

The formation of a socially transmitted food preference (STFP) in rodents requires activation of the guanylyl cyclase-D (GC-D)/necklace glomeruli (NG) olfactory subsystem. During an STFP, an “observer” mouse associates the detection of a novel (“demonstrated”) odor by canonical olfactory sensory neurons (OSNs) with the coincident detection of a social chemostimulus specific for GC-D-positive (GC-D+) OSNs (such as carbon disulfide, uroguanylin (UG) or guanylin). This association results in the acquisition of a preference for the demonstrated odor that can last for weeks. However, it is unclear which CNS circuits are activated by GC-D+ OSNs, mediate the integration of these two signals or consolidate the learned association as a memory. To begin to define brain regions important for GC-D+ OSN responses and the acquisition and consolidation of STFPs, we used c-Fos immunohistochemistry to identify activated neurons after olfactory exposure of behaving mice to the GC-D+ OSN stimulus UG (50 nM) and a general odor, cocoa (2% w/v) in saline. Using stereological approaches, we counted c-Fos+ nuclei within 75 μm of GC-D+ OSN-innervated NGs in the main olfactory bulbs of Gucy2d+/- and -/- mice. Gucy2d+/- mice sacrificed 1 hr after olfactory exposure showed significantly more NG-associated c-Fos+ nuclei than did Gucy2d-/- mice (5.8 +/- 0.9 vs. 1.6 +/- 0.4, p<0.05). No differences were observed in animals that underwent a subsequent preference assay (3 hrs after olfactory exposure to UG and cocoa). UG/cocoa-dependent activation of NG-associated cells showed regional differences, with more dorsal NGs showing greater activation. Together, these results demonstrate that olfactory stimulation of GC-D+ OSNs in behaving mice results in activation of NG-associated olfactory bulb cells.

Analysis Of Lhx5-Driven Gfp Expression In Zebrafish Suggests Early Evolution Of Accessory And Main Olfactory-Like Telencephalic Pathways In Fish
Claudia Tudor , Lydia Waner, Thomas Mueller
Kansas State University, Manhattan, KS, United States

Pheromones are chemical signals that in tetrapods mediate innate reproductive and social behaviors via two complimentary pathways, (1) the main olfactory and (2) the vomeronasal or accessory olfactory pathway. In mammals, vomeronasal sensory neurons (VSNs) express members of 2 large olfactory receptor gene families, V1 receptors (V1Rs) and V2 receptors (V2Rs). V1R ligands are found among low molecular weight molecules, such as steroids, whereas V2Rs recognize peptides. The mitral cells conveying information from V1Rs and V2Rs project into the accessory olfactory bulb (AOB). This structure gives rise to the accessory olfactory tract which projects into the pheromone-responsive medial amygdala (MeA) critical for social behaviors. The main olfactory tract that processes information coming from the main olfactory bulb (MOB) forms a parallel pathway that contributes to pheromone sensation in a complimentary fashion. The evolution of the central olfactory pathways and medial extended amygdala in early vertebrates (fishes) remained ill understood. Although teleost fish like zebrafish lack a vomeronasal epithelium, they do express both main odorant receptors (ORs) and vomeronasal-like V1 (V1R) ora-genes in the olfactory epithelium. To shed light on the central olfactory pathway and their comparative functional organization we analyzed the expression of lhx5-driven GFP in the telencephalon of transgenic the line Tg(lhx5:GFP). The results suggest a mosaic of commonalties and differences to the main and accessory olfactory tract and extended medial amygdala of tetrapods. Our findings will improve the use of zebrafish to study circuits of olfaction and pheromone processing with relevance to social behavior. 

Modulatory Effects Of Serotonergic Input From The Dorsal Raphe Neuclei On The Pyramidal Neurons Of The Anterior Piriform Cortex
Xiaojie Wang1, Dejuan Wang1, Han Du1, Jinshan Xu1, Siqi Jing1, Fan Jia2, Anan Li1
1Jiangsu Key Laboratory of Brain Disease and Bioinformation, Research Center for Biochemistry and Molecular Biology, Xuzhou Medical University, Xuzhou, *, China, 2Center for Brain Science, Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, *, China

Serotonin (5-HT) is a prominent neuromodulator implicated in a variety of brain functions, including not only the control of behavior and regulation of mood but also the modulation of sensory processing. In the olfactory system, 5-HT has been linked to the initial representation and processing of olfactory information. Many previous studies focus on the modulation of 5-HT on the olfactory bulb which receives densely innervation from dorsal raphe nuclei (DRN) 5-HT neurons. Besides the OB, the anterior piriform cortex (aPC), which plays crucial roles in olfactory perception, is also an important target of serotonergic projection. Here we examined the modulatory effects of DRN 5-HT neurons on aPC pyramidal neurons. Our results demonstrated that 5-HT inhibited the firing of aPC pyramidal neurons directly by acting on 5-HT2A and 5-HT2C receptors and this modulation required phospholipase C and calcium-activated potassium channel. The inhibitory effect was confirmed by specific optogenetic activation of axons from DRN 5-HT neurons. Furthermore, fiber photometry recording of calcium signals from the pyramidal neurons showed that endogenous serotonin released by light stimulation of the DRN attenuated both spontaneous and odor-evoked activity of pyramidal neurons. Overall, these findings shed light on the effect of serotonergic modulation on the aPC, and the underlying neural mechanism is identified.

Using Crispr Gene Editing To Investigate The Role Of The Olfactory Bulb In Metabolism
Louis J Colling1, Debra A Fadool1,2,3
1Institute of Molecular Biophysics, The Florida State University, Tallahassee, FL, United States, 2Program In Neuroscience, The Florida State University, Tallahassee, FL, United States, 3Department of Biological Sciences, The Florida State University, Tallahassee, FL, United States

KV channels control neuronal excitability and regulate the ability to perceive external sensory cues. Of these, the Kv1.3 subfamily is highly expressed in the olfactory bulb (OB) where it carries 60% of voltage-activated outward currents in mitral cells (MCs). We have demonstrated that reducing Kv1.3 conductance enhances the excitability of MCs by increasing AP firing frequency. We used CRISPR gene editing, which employs a Cas protein and an engineered guide RNA (gRNA), to generate a conditional knockout of Kv1.3 in MCs. We designed three gRNAs targeted to sequences in the N-terminal region of Kv1.3. To assess the ability of these constructs to alter protein expression, we used a fluorescent GFP-Kv1.3 construct and performed cellular trafficking assays in HEK293 cells. Each gRNA restricted Kv1.3 distribution in >95% of the cells. Each gRNA significantly reduced Kv1.3 current flow without modulating channel kinetics as determined by patch-clamp electrophysiology. gRNA1 was selected due to its proximity to the start codon. We performed a serotyping assay on the OB to determine the appropriate AAV serotype, dosage and route of administration for maximum infection of gRNA1 into MCs. AAV serotypes 2, 5, 6, 8, 9, and 2/retro were compared, as well as multiple dosages via retro-orbital(RO) and direct intracranial injection. AAV9 had the highest infection rate, therefore we generated AAV9-gRNA1 viral particles and RO delivered them to P4 tbet-cre/rosa-cas9 progeny that limit Cas expression to MCs. Currently, mice are sacrificed for slice electrophysiology at P28 to continue characterizing the excitability of the MCs. The above designed viral delivery parameters will permit future metabolic and olfactory phenotyping assessment of tbet-cre/rosa-cas9 progeny with site-specific deletion of Kv1.3 in MCs.

Cell Identity, Membrane Properties, And Spiking Profile Of Rat Olfactory Bulb Dopamine Neurons
Kirill S. Korshunov1, 2, Laura J. Blakemore1, Richard Bertram1, 3, Paul Q. Trombley1, 2
1Program in Neuroscience, Florida State University, Tallahassee, FL, United States, 2Department of Biological Science, Florida State University, Tallahassee, FL, United States, 3Department of Mathematics, Florida State University, Tallahassee, FL, United States

Dopamine (DA) neurons of the olfactory bulb (OB), located in the glomerular layer (GL), are known to contribute to synaptic gating of odor signals and to odor sensitivity. However, their neuronal identity is controversial and their spiking profile has not been fully described. To further characterize these neurons, we used a transgenic rat model (hTH-GFP) in which DA neurons fluoresce. The processes of these neurons vary in length, possibly indicative of two cell types with intra- and interglomerular projections. Using whole-cell electrophysiology, we determined membrane properties of OB DA neurons, which differed between large and small neurons but not between their superficial and deep localization in the GL. Thus, large and small OB DA neurons may be of two cell types. We also determined that OB DA neurons do not fire spontaneously and produce a single spike in response to depolarizing stimuli. This single spiking is likely a direct result of the Na+ currents, as Na+ channels in these neurons quickly inactivate following depolarization and require a long duration to reactivate. A-type K+ and h-currents, also present in these neurons, likely do not directly contribute to this activity. Lastly, their spiking was further examined with different current slopes (ramp stimuli). Steep ramp stimuli produced fewer spikes with higher spike frequency and a larger tonic firing range (the amount of current at which these neurons could spike). Conversely, shallow stimuli produced more spikes with lower spike frequency and a smaller tonic firing range. Given these data, these neurons may be gated by a low-pass filter and may fire more when activated by small stimuli. Given their inhibitory nature, OB DA neurons may be more responsive to, and more likely to filter out, weaker, more tonic odor signals.

Aon Top-Down Projections Modulate Olfactory Processing
Renata Medinaceli Quintela, Lutz Wallhorn, Jennifer Bauer, Daniela Brunert, Markus Rothermel
Department of Chemosensation, AG Neuromodulation, Institute for Biology II, RWTH Aachen University, Aachen, *, Germany

The olfactory bulb (OB) is the target of massive cortical top-down projections from the anterior olfactory nucleus (AON) whose role in modulating early olfactory processing remains elusive. Here, we examined the effect of AON stimulation on both a cellular and behavioral level in anesthetized and awake mice. First, we investigated how top-down projections from the AON modulate OB output neuron activity using electrophysiological recordings in anesthetized mice. Optogenetic activation of AON axon terminals in the OB led to a significant decrease in mitral/tufted cell (MTC) spiking in the absence of inhalation-driven sensory input. Next, we tested for AON modulation effects during odor presentation and found that AON mediated MTC inhibition was independent of the strength and polarity of the odorant response and similar across a variety of odors. Averaged normalized sniff-triggered spike histograms showed a decrease in both baseline and peak spike rate, consistent with an AON mediated effect on odor sensitivity rather than an influence on signal-to-noise ratio. Finally, we tested for behavioral consequences of extrinsically modulating AON activity. In mice, trained to report the presence of odorants, AON stimulation alone failed to evoke a licking response. However, AON activation during odor presentation reliably suppressed odor detection on a fast timescale. This effect was constant across odors and concentrations. Taken together, the strong inhibition of MTC activity observed during electrophysiological recordings might explain the suppression of odor detection observed in the behavioral experiments. These results support the hypothesis that the AON acts as a strong source of top-down input to the OB. Future experiments will focus on studying the effects of light-driven AON inhibition on OB output.

Widespread Odorant Receptor Antagonism Observed In The Peripheral Olfactory System
Jessica H. Brann, Barry J. Evans, Daniel A. Raps, Benjamin C. Smith, Matthew E. Rogers
Firmenich Incorporated, Corporate Research and Development, Plainsboro, NJ, United States

Antagonism of odorant receptors (ORs) is known to occur and it is tantalizing to suggest that its existence alone might imply a role in olfactory perception. However, little is known about how frequently it occurs and how broadly it acts during the combinatorial encoding of odorant mixtures at the periphery. To begin to investigate this we used a semi-automated Ca2+ imaging platform and characterized OR antagonism in populations of dissociated olfactory sensory neurons (OSNs). OSNs were stimulated with binary mixtures of indole and other perfumery ingredients as candidate antagonists and the reduction in indole OSN response due to the other odorant was quantified. Strikingly, statistically significant OSN response inhibition was observed for almost all of the 40 odors tested. To compare whether inhibition predominantly occurred with odorants structurally similar to indole, the test set included odorants chemically similar to, and diverse from, indole. Ingredients from both categories were able to inhibit indole-responsive OSNs with similar strengths and breadths. Furthermore, OSNs were inhibited in a dose-dependent manner and subsets of OSNs affected were highly specific to the odor pair delivered. We therefore postulate that antagonism is a prevalent feature of peripheral olfactory computation, whose combinatorial nature mirrors that of agonism and which may serve to expand the encoding capacity of the system.

Component Qualities Of Stimuli With Double Odors
Lauren Dulieu, Marion E Frank, Thomas P Hettinger
UCONN HEALTH, Farmington, CT, United States

Objective: To determine B-ionone (violet odor) phenotype through recognition of B-ionone in the presence of a reference vanillin (vanilla odor). The bimodal B-ionone odor threshold distribution shows that 40% of humans are non-smellers who require 100 times the concentration for detection (McRae et al. 2013). Due to odor component dominance and mixture suppression (Frank et al. 2017), B-ionone non-smellers would likely perceive vanilla in a mixture of B-ionone and vanilla when the vanillin concentration is 10 times detection threshold and B-ionone 10 times the anti-mode of the threshold distribution. Smellers will likely perceive B-ionone. Methods: Phase 1. Vanillin and B-ionone thresholds for 16, 21-24 year-old subjects were determined. Phase 2: Subjects returned to identify vanillin and B-ionone in binary mixtures with vanillin concentration held constant as B-ionone concentration was varied. T-tests were performed on data from all subjects, non-smellers and smellers of B-ionone. Results: 4 subjects were B-ionone non-smellers (25%) and 12 subjects smellers, a proportion not differing from expected from the literature (p = 0.2206). Subjects’ ability to identify vanilla and violet odors in a series of mixtures were compared. Correct identification of the 10 ppm vanillin + 100 ppb B-ionone mixture differed (t-test, p = 0.0095). Smellers correctly identified this mixture as containing both vanilla and violet odors, while non-smellers only identified a vanilla odor. Conclusions: Presentation of an odor with a bimodal odor threshold against a reference odor can distinguish smeller and non-smeller phenotypes. Odors with a bimodal distribution likely represent Mendelian traits (McRae et al. 2013). The method employed here could efficiently identify odor phenotypes for compounds with double odors.

Odorants In The Environment Are Naturally Sparse
Thomas P Hettinger, Marion E Frank
UCONN HEALTH, Farmington, CT, United States

There may be thousands of potential odorants in the environment, but most are transient or present at too low a concentration to be perceived.  Objectives: To estimate from the laws of probability the average number of detectable odorants in flowers.  Flowers are a conspicuous source of odorants, but many flowers are odorless.  It has been estimated that about half of all flowers are odorless to humans (Hettinger and Frank, Chemosensors 2018, 6(4), 44).  Roses, daffodils, carnations, goldenrods and petunias often have odors, but other flowers such as impatiens, bougainvilleas, orchids, camellias and dahlias are mostly odorless.  Methods: Using simple binomial statistics, we suppose that there are 100 different possible odorant molecules each having a low probability of being detectable in a given flower.  If half of all flowers are odorless, the probability that a particular odorant will be present is only 0.0069, since the probability that all 100 would be absent is (1 – 0.0069)^100 = 0.5.  Results: From binomial calculations it is estimated that that the probability of exactly 0, 1, 2 and 3 odorants being present is 0.5, 0.34, 0.12 and 0.03, respectively, and the probability of 4 or more odorants being present is less than 0.01.  Odorant sparseness is reasonable not only from the human perspective, but also in terms of plant and insect ecology.  If odorants are too sparse, flowers would not be attractive, while if odorants are too dense, flowers would lose their identity.  When several odorants are present, one component will usually dominate because of selective adaptation and mixture suppression (Frank, Fletcher and Hettinger, Chem Senses 2017, 42(7):537-546).  Surveys are needed to determine the extent of sparseness of environmental odors.

Tuning Of Ensemble Responses In The Human Olfactory Cortex To Features Of Odors
Vivek Sagar, Thorsten Kahnt
Northwestern University, Chicago, IL, United States

The human olfactory system transforms chemical information from odor molecules into neural representations of perceptual and motivational features. Neural activity in primary olfactory areas can be used to decode information about odor stimuli but it is unclear which features of odors are encoded in these brain regions that allow us to decode odor information. Here we address this question using functional magnetic resonance imaging (fMRI) and neural encoding models that explicitly model the tuning properties of ensemble responses in primary olfactory areas. We recorded 24 hours of fMRI data from a single human subject while she repeatedly smelled 160 monomolecular odors. We modeled odor-evoked fMRI responses in primary olfactory areas as a linear combination of simpler basis functions, including perceptual (fruity, bakery, fishy, minty, etc.) and chemical properties of odors. Importantly, we then used these models to make out-of-sample predictions about the fMRI responses evoked by odors that were not used to train the model. Preliminary analyses show that accuracy for this out-of-sample prediction was significant in several olfactory areas, including piriform cortex, amygdala, entorhinal cortex and orbitofrontal cortex, indicating that neuronal populations in these areas are tuned to a linear combination of perceptual and chemical properties of the odors. Moreover, hierarchical clustering of weights assigned to perceptual basis functions revealed a large-scale topography of perceptual vs. motivational features, in conjunction with locally distributed encoding of qualitative perceptual features in piriform cortex. Our results show that encoding models can be used to reveal the tuning properties of neuronal ensembles in the human olfactory cortex.

The Molecular And Cellular Basis Of Olfactory Response To Tsetse Fly Attractants
J. Sebastian Chahda, Neeraj Soni, Jennifer S. Sun, Shimaa A.M. Ebrahim, Brian L. Weiss, John R. Carlson
Yale University, New Haven, CT, United States

Dipteran or “true” flies occupy nearly every terrestrial habitat, and have evolved to feed upon a wide variety of sources including fruit, pollen, decomposing animal matter, and even vertebrate blood. Here we analyze the molecular, genetic and cellular basis of odor response in the tsetse fly Glossina morsitans, which feeds on the blood of humans and their livestock, and is a vector of deadly trypanosomes. The G. morsitans antenna contains specialized subtypes of sensilla, some of which line a sensory pit not found in the fruit fly Drosophila.  We characterize distinct patterns of G. morsitans Odor receptor (GmmOr) gene expression in the antenna. We devise a new version of the “empty neuron” heterologous expression system, and use it to functionally express several GmmOrs in a mutant olfactory receptor neuron (ORN) of Drosophila. GmmOr35 responds to 1-hexen-3-ol, an odor found in human emanations, and also alpha-pinene, a compound produced by malarial parasites. Another receptor, GmmOr9, which is expressed in the sensory pit, responds to acetone, 2-butanone and 2-propanol. We confirm that neurons of the sensory pit respond to these odorants, as determined by the first recordings from a sensory pit to our knowledge. Acetone and 2-butanone are strong attractants long used in the field to trap tsetse. We find that 2-propanol is also an attractant for both G. morsitans and the related species G. fuscipes, a major vector of African sleeping sickness. The results identify 2-propanol as a candidate for an environmentally friendly and practical tsetse attractant. Taken together, this work characterizes the olfactory system of a highly distinct kind of fly, and it provides an approach to identifying new agents for controlling the fly and the devastating diseases that it carries.  

Interacting Ig Superfamily Proteins Organize Axon Terminals Of Olfactory Receptor Neurons Regulated By Olfactory Receptors In Drosophila
Qichen Duan1, Yetong Huang1, Scott Barish1, Pelin C. Volkan1,2
1Duke University Department of Biology, Durham, NC, United States, 2Duke Institute for Brain Sciences, Durham, NC, United States

How billions of neurons are assembled into complex neuronal circuits remains largely elusive. The Drosophila olfactory system is an excellent model to address this question. In fruit fly, 50 classes of olfactory receptor neurons (ORNs), each class of which exclusively expresses typically a unique olfactory receptor gene, synapse with their target projection neurons within 50 class-specific and uniquely positioned glomeruli in antennal lobe. How ORN axon terminals of the same class are sorted onto the same glomerulus while separated from other classes is poorly understood. To identify the candidate genes involved in this process, we analyzed the antennal transcriptome data from four stages of the antennal lobe development, showing that many members of two subfamilies of immunoglobulin superfamily proteins, Beat and their heterophilic binding partner Side, are lowly expressed earlier but increase their expression at later stages of glomerular formation. To test if Beats and Sides regulate ORN axon terminal organization to instruct the glomerular positioning, we knocked down single Beat/Side members through RNAi. Perturbing the function of many Beats and Sides in individual, a subset of, or all ORNs led to different local glomerular defects, associated with invasion to neighboring glomeruli, glomerular split or orientation shift, indicating these cell surface Ig proteins regulate the terminal organization of ORN axons in a cell-autonomous and local context-dependent manner. We also observed similar ORN glomerular defects in flies where two developmentally related olfactory receptors are mutated, which showed reduced antennal expression level of some Beat members. Our results suggested that Beats and Sides organize the ORN axon terminals within specific glomeruli regulated by olfactory receptors.

Odorant Receptors Regulate Odorant Receptor Expression In Anopheles Mosquito Olfactory Neurons
Sarah Maguire, Loyal Goff, Christopher Potter
Johns Hopkins University School of Medicine, Baltimore, MD, United States

Olfactory neurons typically express only a single olfactory receptor. In Drosophila, odorant receptor choice for each olfactory neuron is established by signaling cascades early in olfactory neuron development (Barish and Volkan, 2015). In contrast, odorant receptor choice in mammals is more stochastic, and employs a ‘winner-takes-all’ strategy by which expression of a functional odorant receptor suppresses the ability of other odorant receptors to be expressed (Mombaerts, 2004). As such, the current dogma for insects is that mechanisms underlying odorant receptor choice differ greatly between insects and mammals. Surprisingly, we find that ectopic expression of an Anopheles gambiae Odorant Receptor (AgOR) in mosquito olfactory neurons leads to a dramatic loss of endogenous olfactory receptor expression. These experiments were performed in mosquitoes using the Q-system of binary expression we developed (genotype: Orco-QF2, QUAS-AgOR; also see Riabinina, 2016). We used RNA-seq to compare transcript levels in wild-type antennae to those ectopically expressing AgOR in olfactory neurons. Remarkably, ectopic AgOR expression specifically downregulated odorant receptor transcripts. Our results are in stark contrast to similar ectopic OR studies we performed in Drosophila (Chin, 2018). Our data suggests that olfactory neurons of Anopheles mosquitoes employ a currently unexplored mechanism by which odorant receptor expression down-regulates expression of other odorant receptor genes. We will present our latest work investigating how and why ectopic odorant receptor expression in Anopheles mosquitoes leads to changes in odorant receptor expression.

Amplification Of Drosophila Olfactory Responses By A Calcium-Gated Deg/Enac Channel
Renny Ng, Secilia Salem, Shiuan-Tze Wu, Meilin Wu, Hui-Hao Lin, Andrew Shepherd, William Joiner, Jing Wang, Chih-Ying Su
University of California, San Diego, La Jolla, CA, United States

Insect olfactory receptors operate as ligand-gated ion channels that directly transduce odor stimuli into neuronal signals. However, in the absence of any known intermediate transduction steps, it remains unclear whether and how these ionotropic inputs are amplified in olfactory receptor neurons (ORNs). Using single-sensillum recording, we find that amplification occurs in the Drosophila courtship-promoting ORNs through Pickpocket 25 (PPK25), a member of the degenerin/epithelial sodium channel family (DEG/ENaC). Furthermore, knockdown of PPK25 abolishes this amplification. Pharmacological and genetic manipulations indicate that in Or47b and Ir84a ORNs, PPK25 functions as a Ca2+-activated transduction channel via an intracellular calmodulin-binding motif. Additionally, hormonal signaling upregulates PPK25 expression to determine the degree of amplification, with striking effects on male courtship in a courtship competition assay. Together, these findings advance our understanding of sensory neurobiology by identifying an amplification mechanism compatible with ionotropic signaling. Moreover, this study offers new insights into DEG/ENaC activation by highlighting a novel means of regulation that is likely conserved across species.

Starvation Differentially Modulates Gaba Signaling In Olfactory Receptor Neurons
Eryn Slankster1, Dominique Baria1, Roshni Jain1, Seth Odell1,2, Dennis Mathew1,2
1Department of Biology, University of Nevada, Reno, NV, United States, 2Integrated Neuroscience Graduate Program, University of Nevada, Reno, NV, United States

Starvation increases olfactory sensitivity that encourage animals to find food. The molecular mechanisms that underlie starvation dependent modulation of olfactory neuron sensitivity are unclear. Breakdown in these mechanisms lead to abnormal feeding habits, which, in turn, lead to disease states such as obesity. Insulin signaling via insulin receptors (InR) was previously shown to regulate metabolic glucose levels as well as impact neuronal function in the brain. Differential expression of GABAB receptors (GABABR) in Drosophila olfactory receptor neurons (ORNs) was shown to differentially impact ORN function. We analyzed the chemotaxis responses of starved and fed Drosophila larvae to a panel of odorants. We found that starvation modulates food-search behavior in Drosophila larvae. Next, we determined that GABABR localized to terminals of larval ORNs. Genetic manipulation of GABABR and InR levels specifically in ORNs, and GABA levels in surrounding local neurons (LNs) impacted the starvation dependent changes observed during larval chemotaxis. Additionally, manipulating GABABR/InR expression levels in ORNs affected the larva’s ability to find food and led to changes in its body-weight. To identify molecular players downstream of GABABR/InR, we quantified gene expression in the ORNs of starved and fed larvae. A potential target of these signaling events is differential modulation of Orco gene expression in specific ORNs. We propose that interactions between the GABA and insulin signaling pathways are critical to starved-state dependent modulation of ORN sensitivity. Our results offer a mechanistic understanding of how environmental signals are translated into different behavioral outputs based on the animal’s physiological state.

Valence Opponency In Olfactory Processing
Shiuan-Tze Wu, Jen-Yung Chen, Dhruv Grover, Ralph Greenspan, Chih-Ying Su
University of California San Diego, La Jolla, CA, United States

In most sensory systems, neurons are organized into topographic maps which allow for comparison of adjacent inputs via lateral inhibition, to selectively propagate salient information. However in olfaction, it is unclear whether a sensory map exists. Here we address this question by examining the organizing principles underlying paired olfactory receptor neurons (ORNs) in Drosophila. Behavioral assays reveal that ORNs housed within the same sensillum convey information of opposing hedonic value, which in turn mediates attraction or aversion. Remarkably, such valence opponency is broadly observed between different ORN pairs, and is relevant in multiple behavior contexts including egg-laying and courtship. Moreover, at the level of the sensillum, lateral inhibition alone can significantly impact behavior, thus providing a peripheral mechanism for evaluating countervailing olfactory inputs. Together, our results uncover a valence map in the olfactory system, whereby meaningful information from complex odor stimuli is processed at the earliest stage of olfactory coding.

Weighing Taste And Smell In Flavor Preference
Victoria Elliott, Joost Maier
Wake Forest University School of Medicine, Winston-Salem, NC, United States

Food is perceived as a multisensory combination of taste and smell known as flavor. Previous work has sought to uncover the mechanisms underlying multisensory flavor interactions using a wide variety of techniques and model systems. These studies have probed various aspects of flavor perception, such as intensity, detection, etc., yielding mixed results. However, perceptual judgments of flavor stimuli are only indirectly related to final food choice. Therefore, how taste and smell components are combined to inform food choice remains unknown. Here, we used rats as an animal model to investigate the role of congruency and unisensory component liking on multisensory flavor preference. Long-Evans rats were exposed to pairs of taste (saccharin, NaCl, umami, sucrose) and odor (amyl acetate, 2-hexanone) stimuli, creating a wide set of experimentally-controlled (in)congruent flavors. After exposure, a one-bottle testing paradigm was used to directly evaluate preference (consumption) for taste only, odor only and or taste-odor mixtures. Overall, animals did not prefer congruent mixtures over incongruent ones. Rather, we demonstrate that multisensory flavor liking is best predicted by a weighted average of individual component liking. We further show that the degree of weight placed on taste/odor components during multisensory flavor judgement does not depend on component liking, but varies between animals. Ongoing work explores the role of component reliability on taste-odor weighing.

The Role Of Saliva In Caffeine Preference.
Kristen E. Kay, Ann-Marie Torregrossa, Jennifer L. Temple
SUNY University at Buffalo, Buffalo, NY, United States

During consumption, taste compounds mix with saliva before reaching taste receptors. We have previously shown, in animals, that exposure to bitters, such as tannic acid and quinine, can alter salivary protein (SP) profile which then modify taste driven behaviors. Research in humans has demonstrated a correlation between the acceptance of caffeine and the expression of specific SPs. Here we asked if SP expression changes after repeated caffeine exposure and if the changes are predictive of changes in caffeine sensitivity. To do this, we collected saliva samples from adolescents (age 13-17, n=44) with prior caffeine experience. Participants completed taste detection and suprathreshold intensity ratings for caffeine before consuming 500ml of a novel-flavored, sweet, non-caloric beverage containing either placebo (quinine (0.02mg/kg)), caffeine (2mg/kg), or no bitter stimulus for 10 consecutive days. Saliva samples were collected every other day. On the last day, participants completed the taste detection and suprathreshold intensity ratings for caffeine again. Saliva samples were analyzed by gel electrophoresis. We found that participants exposed to a bitter taste maintained bitter detection thresholds while those receiving the non-bitter drink became more sensitive to bitter in the post-exposure period (p=0.041). Linear mixed model analyses showed a strong relationship between detection thresholds and interactions between SP bands that we have previously identified in animal experiments. Interactions between proteins at bands 14, 23, 36, 43, and 83 were significantly related to detection thresholds. In bitter suprathreshold ratings, there was a trend for the bitter-exposed group to rate the two highest concentrations of bitter solutions as less bitter than the control beverage group (p=0.058).

Impact Of Taste And Smell Problems On Diet Quality: The National Health And Nutrition Examination Survey (Nhanes), 2011-2014
Chuan-Ming Li1, Howard J. Hoffman1, Shristi Rawal2, Ashima K. Kant3, Barry I. Graubard4, John E Hayes5, Valerie B. Duffy6
1Epidemiology and Statistics Program, Division of Scientific Programs, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States, 2Department of Clinical and Preventive Nutrition Sciences, Rutgers University, Newark, NJ, United States, 3Department of Family, Nutrition, and Exercise Sciences, Queens College, The City University of New York, Flushing, NY, United States, 4Biostatistics Branch, Division of Cancer Epidemiology & Genetics, National Cancer Institute, Bethesda, MD, United States, 5Department of Food Science, and Graduate Programs in Neuroscience and in Nutrition, Pennsylvania State University, University Park, PA, United States, 6Departments of Allied Health Sciences and Nutritional Sciences, University of Connecticut, Storrs, CT, United States

Chemosensory function varies across people due to biological differences and environmental exposure; such variation associates with differences in liking for and intake of less healthy (sweets, fats, salt) and more healthy (vegetables, high fiber) foods. Consumption of healthy and unhealthy food can be characterized by summary indices of diet quality, such as the Healthy Eating Index (HEI-2015). The National Health and Nutrition Examination Survey (NHANES), a cross-sectional and nationally representative survey, is the primary source of information on the current American diet. We report on associations between self-reported taste and smell function and HEI-2015 scores (higher score indicates better diet quality) among 6,388 adults (≥40 years) from the 2011-2014 NHANES. Self-reported taste/smell function was characterized based on questions about problems during the past 12 months, diminished taste or smell ability since age 25, and phantom odors or unwanted persistent tastes. Older aged adults (70+ vs. 40-69 years), women, higher education (16+ years) and normal body mass index (BMI, versus underweight or overweight/obese) were associated with higher HEI-2015 scores. Adjusting for these variables via regression, we found evidence that self-reported smell and taste problems are associated with lower HEI-2015 scores.  Persistent tastes in the mouth, but not phantom odors, also showed a borderline association with lower diet quality. Among those who completed odor identification tests and supra-threshold intensity ratings of bitter (quinine) and salty (NaCl) tastants (n=3,216; NHANES 2013-2014 cohort), there was no evidence of associations with HEI-2015. These findings suggest  that self-reported problems of smell and taste may be more predictive of diet quality than exam-based assessments.

Do Mice Prefer Caffeinated Or Caffeine-Free Sugar Drinks?
Anthony Sclafani, Austin Vural
Brooklyn College of CUNY, Brooklyn, NY, United States

Most cola drinks contain caffeine, which may enhance their flavor or condition a preference. Here we tested if C57BL/6J mice inherently prefer or acquire a preference for caffeinated sugar drinks. In Exp. 1 mice were tested and trained (24 h/day) with degassed Pepsi (P) and Caffeine-Free Pepsi (CFP). They showed a weak preference for P (60%) before and a weak preference for CFP (59%) after 6 training days. Exp. 2 trained mice with distinctively flavored (grape, cherry) sucrose (11.5%) drinks with caffeine (0.1 mg/g; CS) or without caffeine (CFS) for 10 days. In a subsequent choice test, male mice (n=8) strongly preferred CS to CFS (98%). They also preferred the CS flavor (e.g., grape) without caffeine, indicating that they had acquired a preference for the distinctive flavor not the caffeine in the CS. In contrast, female mice (n=8) showed slight avoidance of the CS with or without caffeine (45%, 40%). Exp. 3 determined if male mice had acquired a true CS preference or a CFS avoidance due to its association with caffeine withdrawal. Naïve male mice were first exposed to flavored sucrose (S) for 6 days. Afterwards, they received flavored caffeine+sucrose (CS) or caffeine-free sucrose (CFS) on alternating days over 10 days. In the final choice tests, the mice preferred CFS to CS (74%), S to CS (98%) and S to CFS (84%). These results indicate that caffeine withdrawal conditioned an avoidance to CFS in Exp. 2. Initial exposure to flavored sucrose without caffeine resulted in Exp. 3 mice learning a stronger aversion to CS than to CFS. Thus, with 24-h training, caffeine withdrawal significantly influences the response to caffeine and caffeine-free sugar drinks. The different response of male and female mice is consistent with reported sex differences in caffeine reinforcement in humans.

Strategy For Recombinant Expression Of Soluble Functional N-Terminal Domain Of Human Sweet Taste Receptor Produced In Escherichia Coli
Christine Belloir, Nicolas Poirier, Lucie Moitrier, Fabrice Neiers, Loïc Briand
INRA, CNRS, AgroSup Dijon, Université de Bourgogne Franche Comté, Dijon, *, France

The human sweet taste receptor is a heterodimeric receptor composed of the two distinct protein subunits, TAS1R2 and TAS1R3 (class C of G protein-coupled receptors). These subunits possess a large N-terminal domain (NTD) linked to the heptahelical transmembrane domain by a short cysteine-rich region. TAS1R2-NTD has been shown to bind naturals sugars and some sweeteners including sucralose, neotame, and acesulfame-K. However, TAS1R2-NTD binding properties remain largely unknown. A prerequisite for biochemical and structural studies is the production of large amount of purified TAS1R2-NTD. Here we report the successful expression and purification of functional human TAS1R2-NTD expressed in Escherichia coli. TAS1R2-NTD was expressed as a fusion with the Small Ubiquitin-like MOdifier (SUMO) protein. The soluble protein was then purified and characterized. Circular dichroism and SEC-MALS analysis showed that TAS1R2-NTD was properly folded. Intrinsic fluorescence spectroscopy demonstrated that TAS1R2-NTD is able to bind sweet compounds with physiological affinities. This expression strategy should facilitate the characterization of TAS1Rs ligand interactions.

Interactions Of Estrogen And Trpm5 Channels In Fat Taste
Naima/s Dahir1,2, Yan Liu2, Fangjun Lin1,2, Timothy/A Gilbertson2
1Burnett School Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, United States, 2Department of Internal Medicine, College of Medicine, University of Central Florida, Orlando, FL, United States

Transient Receptor Potential channel type Melastatin 5 (TRPM5) is a nonselective cation channel that is activated by an increase in cytosolic calcium. TRPM5 channels are highly expressed in taste receptor (Type II) cells that transduce bitter, sweet, umami, and fatty acid compounds. While the function of TRPM5 channels is well-defined in these cells, the effects of hormones such as estrogen on TRPM5-mediated signaling that impact the taste system are not well known. We investigated TRPM5 channel activation in fatty acid-sensing cells and the physiological impact in long-term fat intake in males and females. This study followed from our earlier work where we showed a sex difference in TRPM5-deficient (TRPM5-/-) animals and their wild type (WT) counterparts on a 60% high-fat diet. TRPM5-/-  male mice consumed less calories and subsequently gained less weight and body fat than their WT counterparts. In contrast, TRPM5-/-  female mice gained less body weight and body fat while having equal caloric intake with WT females. We found that removing the secretion of estrogen via ovariectomy in the TRPM5-/- females changed their weight status; they gained the same amount of weight and body fat as the TRPM5-/- males while not altering their caloric intake. At the taste cell level, we found that estrogen increased fatty acid-induced Ca2+ responses in both TRPM5-/- and their WT counterparts. Interestingly, this difference was papillae-specific in the TRPM5-/- females; circumvallate taste cells showed no increase in fatty acid responses when estrogen was present. Fungiform taste cells displayed a striking increase in cytosolic calcium in TRPM5-/- but not in WT females. Together, these results demonstrate a link between estrogen and TRPM5-mediated signaling in feeding behavior and taste cells that is both sex and papillae-specific. We are conducting additional experiments to better understand the mechanistic interactions between estrogen receptor activation and taste signaling via TRPM5 channels.

Sweet Taste Detection, Preference And Manipulation In Tree Shrews (Scandentia,Tupaia Belangeri)
Erin E Maher1, Naini Shiswawala1, Anila Tynan1, Heywood Petry2, Alev Erisir1
1University of Virginia, Charlottesville, VA, United States, 2University of Louisville, Louisville, KY, United States

Mammalian taste behavior has numerous in-group similarities, including a preference for sweet taste. Although most of these similarities exist between primates and rodents, there also exist a few notable differences in taste detection between these two species. A major difference of interest involves the compound lactisole, a chemical used to decrease sweet perception in some processed foods.The receptor for sweet taste in mammals is made up of two members of the T1R class of GPCRs, T1R2 and T1R3 that form a dimer together. Lactisole functions by competitively binding to the transmembrane domain of T1R3 to block sweet taste in humans, but is ineffective in binding to T1R3 in rodents. Tree shrews, the closest phylogenetic relative to primates, have evolved a sweet taste receptor that more closely resembles that of primates than rodents. In this study, we first identified similarities and differences in the amino acid composition of T1R3 transmembrane domain between primates, rodents and tree shrews. We  next utilized a four bottle preference test to characterize the activity, sucrose consumption, and effect of lactisole on tree shrew taste behavior. Our results demonstrate tree shrews have a strong preference for the taste of sucrose that increases with concentration. We also found that tree shrews show both a reduction in consumption rate as well as a loss of sucrose preference when given lactisole in combination with sucrose, suggesting that lactisole blocks sweet taste in tree shrews. These behaviors in the tree shrew show this species may be a good model for other tastant studies that involve artificial sweeteners and lactisole. These results also suggest that along with gustatory anatomy, tree shrew taste behavior can be used as a model for primate taste preference and aversion behavior.   

Fructose Signal Transduction In Cultured Human Fungiform Taste Papillae (Hbo) Cells
M. Hakan Ozdener, Evangeline Adjei-Danquah, Robert F. Margolskee
Monell Chemical Senses Center, Philadelphia, PA, United States

Fructose and fructose derived products are a significant component of the human diet and have been related to diabetes as well as insulin resistance. Although there are many reports on how fructose is absorbed and transported in the intestine, it is not known if such transporters in human taste cells might contribute to how we detect fructose. We examined which receptors, transporters and metabolic pathways might play a role in fructose detection by taste cells using cultured human fungiform taste (HBO) cells. Using Ca++ indicator or the voltage sensitive membrane dyes, we found that HBO cells responded in a dose-dependent manner to increasing concentrations of fructose. Blocking TAS1R3 with lactisole and knocking down glucose transporter 5 (Glut5), known to transport fructose, by siRNA significantly decreased responses of HBO cells to fructose, indicating that human taste cells detect fructose by TAS1R3 and Glut5. Pharmacological modulators of the KATP channels did not alter HBO cell responses to fructose indicating that they are not involved. In conclusion, human taste cells respond to fructose via TAS1R3 and Glut5 but not KATP.

Modulatory Effect Of Arginyl Dipeptides On The Frequency Of Nacl Elicited Responses In Cultured Human Fungiform Taste Papillae (Hbo) Cells
Jiao-Jiao Xu1, Andrew I. Spielman2, Hau Y. Chung3, M. Hakan Ozdener1
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2College of Dentistry, New York University, New York, NY, United States, 3The Chinese University of Hong Kong, Hong Kong, *, Hong Kong

Salty taste is one of the five basic tastes and is often elicited by NaCl. Because excess sodium intake is associated with many health problems. Identifying salt taste modulators will provide a potent boost to salty taste which may result in having safe and well-liked sodium chloride enhancers that improve human health.  In this study, we investigated the role of arginyl dipeptides on NaCl-induced responses in cultured human fungiform taste papillae (HBO) cells. We examined five arginyl dipeptides and two non-arginyl dipeptides. Found only Ala-Arg (AR), Arg-Ala (RA), Arg-Pro (RP) dipeptides significantly increased the number of cell responses to NaCl, whereas no effect was observed with others. Pharmacological studies showed that AR significantly increased responses of amiloride-sensitive but not amiloride-insensitive cells. In studies using small interfering RNAs (siRNAs), responses to AR were significantly decreased in cells transfected with siRNAs against epithelial sodium channel ENaCα or ENaCδ compared to untransfected cells. Altogether, AR increased responses of amiloride-sensitive cells required ENaCα and ENaCδ. 

9:00 - 10:00 AMEstero Foyer
Coffee Break

9:00 - 12:00 PMOffsite - IMAG
Outreach Event

10:00 - 12:00 PMCalusa FGH
Fat facts: an update on fat perception and its dietary consequences

Chair(s): Sanne Boesveldt



Sanne Boesveldt
Wageningen University, Wageningen, *, Netherlands

History And Physiology Of Fat Taste Perception. What We Know And Don'T Know
Nada Abumrad
Washington University


Why Am I (Not) Sensitive To Fat Taste? Do Adiposity And Diet Play A Role?

Robin M. Tucker
Michigan State University

Fat taste detection thresholds vary widely between and within studies. A variety of factors have been proposed to explain these differences. This presentation focuses on the state of the science regarding associations between fat taste sensitivity and adiposity as well as dietary intake. Areas ripe for future exploration will be discussed.


From Genes To Neurons: How Flies Get Fat

Tania Reis
University of Colorado

Little is known about how the brain communicates with the periphery to regulate complex physiological and behavioral processes. Metabolism is an integrated, multi-organ process, and is best studied within the context of the whole organism. Signals between disparate tissues and organs are processed in the brain to coordinate, among other things, rates of food consumption and storage of energy as fat. To maintain organismal energy homeostasis, the underlying circuits should also respond to the nutritional content of the diet, but these circuits and the mechanisms by which they control fat storage are incompletely understood. We previously used an unbiased genetic screen to identify 66 genes that when mutated increase body fat in Drosophila larvae. One such gene, the RNA-binding protein alan shepard (shep), has no characterized role in metabolism. We find that knockdown of shep in the brain phenocopies the high-fat phenotype of the mutant and drives changes in the complex metabolic behaviors of feeding and locomotor activity. Additionally, knockdown of shep in the fat body, where most fat is stored, results in a lean phenotype accompanied with a modest increase in locomotor activity. The Shep locus encodes multiple transcript and protein isoforms. We find effects on fat storage of fat body-specific overexpression of a specific Shep isoform, whereas neuron-specific overexpression of the same isoform has no phenotype. Thus Shep isoforms have tissue-specific functions in metabolism. We further find that levels of specific Shep isoforms are regulated in a nutrient-dependent and tissue-specific manner. Our work is now focused on determining the role of Shep isoforms in different organs in regulating overall organismal energy metabolism in response to dietary nutrition. 


The Brain As A Fat Sensor? Neuronal Correlates Of Nutritional Fat Intake

Sabine Frank-Podlech
University of Tubingen

The brain as a fat sensor? Neuronal correlates of nutritional fat intake

Sabine Frank-Podlech1-3, Jörg Hinrichs4, Andreas Fritsche2,3, Hubert Preissl2,3,5,6

1 Institute for Medical Psychology and Behavioural Neurobiology, University of Tübingen, Tübingen, Germany

2 Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen; German Center for Diabetes Research (DZD), Tübingen, Germany

3 Department of Internal Medicine IV, University Hospital, Tübingen, Germany

4 University of Hohenheim, Dep. Soft Matter Science and Dairy Technology, Stuttgart, Germany

5 Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany

6 Department Pharmacy and Biochemistry, Faculty of Science, University of Tübingen, Tübingen, Germany


Neuroscientific studies showed that the perception and the neuronal processing of food is a complex interaction of different neuronal systems. The main control region of energy homeostasis is the hypothalamus, however also gustatory, reward and cognitive control regions are involved in neuronal food processing. In my talk, I will present human neuroimaging studies showing that fat ingestion leads to neuronal activity changes up to hours after ingestion. The metabolic effects are mainly represented in the homeostatic system, yet fat might be a modulator of the homeostatic and the gustatory system. But also pure taste components can induce alterations in neuronal activation patterns. Therefore, acute neuronal fat processing is highly dependent on the flavor and texture of the stimuli. Findings on neuronal processing of fat aroma suggest that it might be possible to simulate fat-triggered sensations in the brain on the gustatory level by fat-free aroma components of olive oil, possibly by previously learned associations. Furthermore, the question arises how oral fat taste perception is associated with such neuronal activation patterns. First results investigating this questions, hint towards altered neuronal connectivity patterns dependent on the interaction of individual oral fat perception and acute intake of a high- vs. a low-fat meal in homeostatic, reward and somatosensory regions. Hence, the multiplicity of fat perception is also represented in neuronal activation patterns.

10:00 - 12:00 PMCalusa ABC

Chair(s): Gerard Coureaud and Donald Wilson



Donald Wilson
NYU School of Medicine

abstract not appropriate for Instroduction


The Role Of Multisensory Overlap For Configural Processing Of Food Flavor In Humans: Behavioral Markers And Neural Correlates

Janina Seubert
Karolinska Institute

Odors form part of the complex sensory experiences during food consumption and during recognition of food in the environment, creating a learned link between a food’s nutritional value and its outward appearance. Associative learning about configural contingencies within these complex sensory stimuli is thus thought to be crucial for adaptive choices about food intake; indeed, familiar stimulus combinations tend to evoke appetite, while unfamiliar combinations elicit avoidance behavior. The more ecologically relevant assessment of subtle deviations between learned associations and novel complex sensory stimuli is, however, to date poorly understood, both in terms of its associated perceptual experiences and its cortical processing. To address this, we studied perceptual acuity to variations in olfactory-gustatory and olfactory-visual sensory overlap, its behavioral relevance, and potential underlying perceptual and functional-anatomical mechanisms. Our data show that humans are highly sensitive to variations in crossmodal perceptual overlap, and that this sensitivity is directly behaviorally relevant for the emotional appraisal of complex chemosensory stimuli. We further delineate a top-down controlled cortical pathway that supports the formation of such assessments during conditions of perceptual difficulty.


A Competitive Binding Model Predicts The Response Of Mammalian Olfactory Receptors To Mixtures

Vijay Singh
University of Pennsylvania

Most natural odors are complex mixtures of many odorants, but due to the large number of possible mixtures only a small fraction can be studied experimentally. To get a realistic understanding of the olfactory system we need methods to predict responses to complex mixtures from single odorant responses. To meet this challenge, we develop a biophysical model that predicts mammalian receptor responses to complex mixtures using responses to single odorants. The dominant nonlinearity in our model is competitive binding: only one odorant molecule can attach to a receptor binding site at a time. This simple framework predicts receptor responses to mixtures of up to twelve monomolecular odorants to within 15% of experimental observations and provides a powerful method for leveraging limited experimental data. We first fit a dose-response relationship to individual odor responses and then use those parameters in a competitive binding model to predict mixture responses. Extensions of our basic model with odorant interactions lead to additional nonlinearities observed in mixture response like suppression, co-operativity, and overshadowing. We demonstrate that the presence of such interactions can be identified via systematic deviations from the competitive binding model, thus providing a framework for characterizing nonlinearities from mixture response data.


From Neuron To Behavior: Response Of Parasitic Wasps To Mixtures Of Plant-Associated Odors

Tolulope Morawo
Auburn University

From Neuron to Behavior: Response of Parasitic Wasps to Mixtures of Plant-Associated Odors

Tolulope Morawo, Prithwiraj Das, Esther Ngumbi, Henry Fadamiro

Auburn University, Auburn AL 36849 USA



Parasitic wasps (parasitoids) are beneficial insects that rely on odor cues for resource location. Host location cues are often encountered as multi-component odor blends from herbivore and infested plants. We investigated the perception of plant-associated odorants at the neuronal, antennal and behavioral levels in two parasitoid species, Microplitis croceipes and Cotesia marginiventris. Both species are parasitoids of lepidopteran larvae but with different degrees of host specificity. The responses of olfactory sensory neurons (OSNs) in the antennal sensilla placodea of female parasitoids to plant volatiles and mixtures were tested in single-sensillum recordings. In both parasitoid species, OSNs showed excitatory activity to linalool and cis-3-henenol when presented individually. However, a binary mixture of both compounds inhibited OSN activity in M. croceipes, but not in C. marginiventris, suggesting a difference in the perception of the odorant mixture (configural versus elemental). In another study, we recorded electroantennogram (EAG) response of parasitoids to the pheromone components (Z11-16 Ald and Z9-14 Ald) of Heliothis virescens, a common host. Microplitis croceipes showed greater EAG response than C. marginiventris to individual components. Subsequently, a blend of the two pheromone components elicited much higher EAG response in M. croceipes, but not in C. marginiventris, suggesting a general pattern of elemental perception. This result was in agreement with another related study in which a binary mixture of α-pinene and cis-3-hexenol elicited an additive effect in the attraction of M. croceipes, but not in C. marginiventris. These differences may have implications for odor discrimination in the two parasitoid species, especially in relation to their host selection strategies.


Configural Perception Of Odor Mixtures: Functional Early In Life, Convergent Between Species

Gerard Coureaud1, Donald A. Wilson2
1CNRS - Lyon Neuroscience Research Center, 2NYU School of Medicine

Odors that animals - including humans - perceive arise most commonly from complex mixtures of odorants rather than from single odorants emitted alone. This is true all across the life span. To cope with this complexity, organisms may process odor mixtures elementally or configurally. Elemental perception means that a mixture is perceived through one or several of its components. Configural perception implies that a mixture is perceived as a whole, i.e., as an object (like food, flower, conspecific) carrying its own and specific odor, distinct from the odors of the components. The biological rules and neural mechanisms governing the configural perception of odor mixtures remain poorly understood, in both vertebrates and in invertebrates. Another intriguing issue concerns the possibility that the same mixture may be perceived through the same mode by different species. For several years, we have been exploring that issue in various species, in particular using a binary AB mixture of ethyl isobutyrate (A) and ethyl maltol (B). In human adults, while A smells like strawberry and B like caramel, the AB mixture promotes the perception of a completely different odor, an odor of pineapple. This configural perception occurs at the 30/70 ratio of A/B; if it is changed, the perception becomes elemental. Here, we will present a series of results obtained at different levels, from the peripheral to the central and behavioral levels, and in distinct paradigms, pinpointing a convergence in the way the AB mixture at the 30/70 ratio is perceived in newborn rabbits and adult mice, in addition to humans. Stable rules may, thus, exist for configural odor perception of certain mixtures across species, which is consistent with the common necessity for all organisms to simplify the surroundings’ chemical complexity.

12:00 - 1:00 PMLunch On Own
Lunch On Own

1:00 - 2:00 PMCalusa ABC
ACHEMS Business Meeting

Get involved! Join us for reports from the society leaders on the state of the Association. All members welcome and encouraged to attend.

2:00 - 3:30 PMGreat Egret

Chair(s): Sanne Boesveldt and Thomas Hummel

Thomas Hummel Interdisciplinary Center For Smell And Taste, Department Of Otorhinolaryngology, “Technische UniversitäT Dresden”, Dresden, Germany

Katherine Whitcroft Royal National Throat Nose And Ear Hospital And University College London&Semi; Centre For The Study Of The Senses, Institute Of Philosophy School Of Advanced Studies, University Of London

Kathrin Ohla Group Leader Cognitive Electrophysiology Cognitive Neurosciences - Institute Of Neuroscience And Medicine (Inm-3) Research Center Juelich Juelich, Germany

Johannes Frasnelli Department Of Anatomy, Université Du QuéBec à Trois-RivièRes, Trois-RivièRes, Canada

2:00 - 4:00 PMCalusa ABC

This workshop will include an overview of research, training, and funding opportunities for graduate students, postdoctoral fellows, and early stage investigators. The discussion will provide practical information on how grant applications are processed within NIH/NIDCD, including Institute and study section assignments, the peer review process, Advisory Council activities, pay lines, and the roles of program and review staff.

4:00 - 6:00 PMCalusa ABC/ Calusa Foyer
Career Panels/Networking Social

The Mentoring/Networking committee will hold a panel discussion on academic careers as laboratory PIs in different types of institutions, from 4:00pm-5:00pm on Tuesday, April 16th. Afterwards please join us for food, drink, and a chance to talk with others in your field, in a more casual surrounding. This is a great opportunity for advanced graduate students and postdocs.

7:00 - 9:00 PMCalusa ABCD


Blood Sweat And Tears: Human Social Chemosignaling In Health And Disease

Noam Sobel
Weizmann Institute of Science

Most animals communicate using social chemosignals, namely chemicals emitted by one member of the species, which then produce chemical and behavioral changes in other members of the species. Such communication is prevalent in insects and terrestrial mammals, and mounting evidence implies that it is also common in human behavior, albeit primarily at a subliminal level. Human social chemosignals may be responsible for a host of effects, ranging from the contravercial driving of menstrual synchrony in women, and on to the widely replicated conveying of fear across individuals. Here I will describe our findings on mechanisms of human chemosignaling in both health and disease. Based on these findings I will argue that in contrast to common notions, humans are highly olfactory animals.


How We Taste: Otop1 And The Mechanism Of Sour Transduction

Emily Liman
University of Southern California


Systems For Encoding Odor Valence And Motivating Approach Behaviors

Daniel Wesson
University of Florida

Odors may elicit strong emotional (do I like it?) and behavioral responses (should I approach it?) – phenomena well-known to be strengthened with learning. Here we investigated the neural systems responsible for associating odors with their learned outcomes and also sought to link those neural systems with displays of reinforcement-based approach behaviors. First, we investigated the representation of odor-reward associations throughout and within two areas recipient of dense olfactory input using multi-site electrophysiological recordings and separately, fiber photometry from mice engaged in a reward-based olfactory learning task. As expected, neurons in both the posterior piriform cortex (pPCX) and olfactory tubercle (OT) represented odor valence, yet the recruitment of neurons by conditioned rewarded odors was distinctly pronounced in the OT. The photometry results revealed that odor valence coding occurs among D1- but not D2-type OT medium spiny neurons – the principal neuron type in the OT. In both the recordings and imaging, statistically meaningful changes in activity occurred prior to behavioral responses. Finally, we show that activation of DAergic terminals in the OT and OT D1-MSNs supports reward-motivated approach behaviors. All together our results contribute to a model whereby OT D1 MSNs support ollfactory valence and ultimately hedonic-based behavioral responses.


Building A Mosquito Sensory System To Hunt Humans

Leslie Vosshall
The Rockefeller University

My group is interested in the molecular neurobiology of mosquito host-seeking behavior. Female mosquitoes require a blood meal to complete egg development. In carrying out this innate behavior, mosquitoes spread dangerous infectious diseases such as malaria, dengue, Zika, chikungunya, and yellow fever. Humans attract mosquitoes via multiple sensory cues including emitted body odor, heat, and carbon dioxide in the breath. The mosquito perceives differences in these cues, both between and within species, to determine which animal or human to target for blood-feeding. We have developed CRISPR/Cas9 genome-editing in the Aedes aegypti mosquito with the goal of understand how sensory cues are integrated by the female mosquito to lead to host-seeking behavior. Some of the questions we are currently addressing are: Why are some people more attractive to mosquitoes than others? How do insect repellents work? How are multiple sensory cues integrated in the mosquito brain to elicit innate behaviors? How do female mosquitoes select a suitable body of water to lay their eggs? Recent advances from my group in analyzing the molecular biology of host-seeking behavior will be discussed.

9:00 - 11:00 PMEstero Ballroom
Poster Session IV

Continuous Tracking Of Memory Formation Recording Of Gustatory Cortex Neuronal Ensemble Activity Following Conditioned Taste Aversion In Freely Behaving Rats
Elor Arieli1, Nadia Younis1, Daniel Udi1, Anan Moran1,2
1Department of Neurobiology, Faculty of Life Science, Tel Aviv University, Tel Aviv, *, Israel, 2Sagol School of Neuroscience, Tel Aviv University , Tel Aviv, *, Israel

Neuronal activity in sensory cortices changes following learning, such as in the gustatory cortex (GC) after conditioned taste aversion (CTA) wherein a novel palatable taste becomes aversive following pairing with malaise. These changes, however, have been found using "snap shots" taken 24 hours apart, and thus do not allow fine temporal description of the response changes over time. Insights about the time course of these changes come from molecular studies showing different molecular cascades that span over hours following the CTA induction. To reveal the neuronal activity changes over time we implanted rats with electrodes in the GC and intraoral cannula for precise taste deliveries, and tracked ensembles of neurons for 48 hours; before, during and after CTA. Our results show that changes in neuronal response dynamics start approximately 1h after CTA induction and end about 8h post CTA, with the main changes occurring 3-6h post CTA. This timing is similar to time of the reported molecular processes. Interestingly, these changes were uncorrelated with changes in their baseline (BL) activity over time. In contrast, high correlations were observed in BL and taste response activity between different neurons, supporting the idea of global changes that govern neuronal activity following learning. Additional analyses of network level synchrony and delta-gamma modulation show similar increases 3 hours post CTA. Together, our results show that long-term electrophysiological changes that occur following taste aversion learning occur in the same time scales of the molecular processes. Moreover, these changes seem to be mainly governed by a network level organization and to a lesser extent by the state of the single neuron.  

Quantification And Characterization Of Taste Cells In Mouse Circumvallate Taste Buds.
Yannick K Dzowo1, 2, Ruibiao Yang1, Robert S Lasher1, Thomas E Finger1, 2
1Rocky Mountain Taste & Smell Center, University of Colorado School of Medicine, Aurora, CO, United States, 2Modern Human Anatomy Program, Univ. Colorado Anshutz Medical Campus, Aurora, CO, United States

Taste buds in mice encompass four types of taste cells: 3 elongate types: type I, type II, type III; and basally-situated post-mitotic cells (type IV). The bud is surrounded by edge and non-taste epithelial cells while progenitor cells lie outside of the taste bud along the basement membrane. Taste cells have several characteristics which are used to divide them into different types. Type I cells are characterized by an indented and elongated nucleus with invaginations, folded membrane, and distinctive apical microvilli (short and tall) in the taste pore. Type II cells are spindle-shaped and characterized by a large round or oval nucleus, a single apical microvillus, which extends through the taste pore, and specialized “atypical” mitochondria at functional points of contact with nerve fibers. Type III cells are slender and characterized by a single apical microvillus extending through the taste pore, an elongate, indented nucleus and synaptic vesicles gathered at points of contact with nerve fibers. Type IV cells (non-proliferative “basal cells”) have a nucleus in the lower third of the taste bud, do not extend to the taste pore, and although irregularly shaped, are elongated in the axis of the taste bud, with a foot processes extending to the basement membrane. Based on these characteristics, we used the series images of taste buds created by serial blockface SEM to quantify the percentage of the different cell types in 4 taste buds. Type I cells represent just over 50% of the overall cell counts, whereas type II, type III, and basal cells represent 18%, 15%, and 15% respectively. In summary, use of 3D Reconstruct software on sbfSEM data has allowed us to attain accurate quantifications and morphological descriptions of taste cell types in circumvallate taste buds.

Next Generation Neural Interfaces For Biophotonic Medicine
Samuel F. Littich1, Arjun K. Fontaine1, Gregory L. Futia1, Nicole L. Arevalo 2, John H. Caldwell2, Emily A. Gibson1, Diego Restrepo2, Richard. F. Weir1
1CU Denver, Anschutz Medical Campus, Department of Bioengineering, Aurora, CO, United States, 2CU Denver, Anschutz Medical Campus, Department of Cell and Developmental Biology, Aurora, CO, United States

Electrical stimulation of the autonomic nervous system is increasingly used to treat human disease. Vagal nerve stimulation is used in care for epilepsy, depression, and heart failure. Sympathetic modulation has been effective for PTSD, ventricular arrhythmias, and complex regional pain syndrome. Autonomic modulation shows promise to treat many more pathologies, however, our understanding of the circuits that underlie these treatments is woefully imprecise. In part, this ignorance is due to the complexity of the control and feedback of autonomic circuits that affect almost all visceral organs. Investigating this complexity has proven difficult with existing techniques; electrical stimulation lacks the ability to selectively activate, inhibit, and record from subsets of autonomic neurons. Therefore, we have begun to develop an optical system that can stimulate and record at the single neuron and axon level in the anesthetized mouse, with the goal of doing this in the awake, behaving animal. Optogenetic “read in” and “read out” of neural activity at individual axons of the vagus and cell bodies of sympathetic neurons will aid precise neural mapping of autonomic motor and sensory circuitry. To that end, inexpensive, scalable, and reusable vagus nerve and superior cervical ganglion cuffs with an integral gradient index lens were designed to enable those experiments. These cuffs can markedly reduce movement artifacts from systolic pulse in the carotid and the respiratory perturbations of the trachea despite the close proximity of these structures to each other. This improved image stability has been utilized for patterned stimulation of opsins and to image calcium signals from genetically encoded calcium indicators. Work continues to adapt the neural interface for wider use.

Odorant Interactions With Model Membrane Systems
Troy W Lowry1, Debra A Fadool1, Steven Lenhert2
1Department of Biological Science and Program in Neuroscience and Institute of Molecular Biophysics, Tallahassee, FL, United States, 2Department of Biological Science and Integrative Nanoscience Institute, Tallahassee, FL, United States

Since the discovery that odor receptors (ORs) are GPCRs, significant efforts have been made to identify odorant binding sites through the development of better expression systems and functional assays, with emphasis on OR binding activity.  Unlike other GPCRs, the OR binding site has not been identified, leaving a gap in our molecular understanding of odorant interactions. Interestingly, odorants have also been observed to interact strongly with model membrane systems in the absence of ORs.  Herein, we present experiments designed to test the hypothesis that the odorant binding site may in fact lie in the membrane itself, which upon odorant binding triggers OR-based signal transduction allosterically. For our purpose we used a novel model membrane assay based on surface-supported lipid multilayers, which have controlled topographical and lateral features printed from the recesses of a patterned stamp, to expose lipids to odorants in solution.  In this way, lipid pattern fidelity could be monitored in situ using both fluorescence and label-free methods.   The water soluble odorant, lilial, was used to demonstrate unique lipid multilayer nanopattern dissolution, resulting in decreased fluorescence uniformity and intensity compared to that of the control analyte - ethanol.  Fluorescence recovery after photobleaching of lipid bilayers demonstrated changes in the fluorescence recovery (~ 55% bleaching and recovery to about ~ 85%) compared to bilayers in pure water, which bleached to ~ 80% and fully recovered.  The assay is shown to work with hydrophobic odorants, such as carvone.  Currently in the works are concentration curves and established assays for the binding activity of enantiomers. Our results suggest that the lipid bilayer may play a larger role in odorant binding than previously thought.

Interpretation Of The Spatial-Temporal Structure Of Turbulent Chemical Plumes For Odor Tracking
Brenden Michaelis1, Yuriy Bobkov2, Jose Principe2, Barry Ache2, Il Park3, Tom Matthews4, Matthew Reidenbach1
1University of Virginia, Charlottesville, VA, United States, 2University of Florida, Gainsville, FL, United States, 3SUNY Stony Brook, Stony Brook, NY, United States, 4Florida Fish and Wildlife, Marathon, FL, United States

Animals often use their sense of smell to locate food, identify mates and predators, and find suitable living habitats. Odor molecules are often dispersed from their source by turbulent wind or water currents. In both terrestrial and aquatic environments, the instantaneous temporal and spatial distribution of odors is complex, and odor plumes are often composed of filaments of chemicals at high concentrations that are adjacent to fluid with little or no odor. Navigation in turbulent chemical plumes has typically been considered a spatial information problem where individuals aim to path towards higher concentration. Concentration information alone is too irregular in turbulent plumes, particularly in water, to explain search speed and accuracy of many animals that undergo search. Recent discoveries of bursting olfactory neurons in the spiny lobster, Panulirus argus, suggest a mechanism for accurately sampling the temporal structure of chemical signals. Lobster pathing behavior in small scale flume experiments is compared to the time series of encountered odor concentration at the antennules, as measured by planar induced fluorescence. Reactions to the intermittent signal are quantified by measuring changes in search speed and trajectory in response to the encountered plume. We observe that decisions in a lobster’s search are better explained by a combination of concentration and temporal cues than concentration cues alone. We believe that considering the temporal element of chemical cues, such as intermittency encoding, is necessary to provide plume information on time scales relevant for informing efficient search behavior.

Cell Non-Autonomous Requirement Of P75 In The Development Of Geniculate Chemosensory Neurons
Christopher R. Donnelly, Tao Tang, Amol Shah, Robert M. Bradley, Charlotte M. Mistretta, Brian A. Pierchala
Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, United States

During development of the peripheral taste system, chemosensory neurons of the geniculate ganglion project via the chorda tympani (CT) to innervate taste buds (TBs) in fungiform papillae in the anterior tongue. Germline deletion of the p75 neurotrophin receptor results in dramatic axon guidance and branching deficits. This leads to a loss of geniculate neurons during the period of target-dependence, and a loss of fungiform papillae and TBs.  A recent examination of p75 in development of DRG sensory neurons revealed that neural deletion of p75 has a significantly milder effect on DRG survival than germline p75 deletion, suggesting that much of the developmental effects of p75 relate to its function in non-neuronal cell types that contribute to the sensory circuit, such as Schwann cells. To determine whether the developmental functions of p75 in geniculate neurons are cell autonomous, p75 was deleted specifically in Phox2b+ chemosensory neurons (p75f/f; Phox2b-Cre) or in neural crest-derived cells (p75f/f; P0-Cre). Surprisingly, there was no loss of geniculate neurons in either p75f/f; Phox2b-Cre or p75f/f; P0-Cre mice. There was a significant decrease in the number of fungiform taste buds in p75f/f; Phox2b-Cre mice, and less of an effect in p75f/f; P0-Cre mice. An ongoing examination of the chemosensory innervation of fungiform TBs suggests that there is no loss if innervation in p75f/f; P0-Cre mice, and only a modest effect in p75f/f; Phox2b-Cre mice. Continuing studies include recordings of CT responses to lingual stimuli in both p75 germline and conditional knockout mice. Taken together, these data suggest that the axon growth and pathfinding functions of p75 are cell non-autonomous, and require p75 expression in other cell types of the chemosensory circuit, such as glial and target cells. 

Exposure To Il-13 Increases Number Of Solitary Chemosensory Cell Markers In Primary Nasal Epithelial Air-Liquid Interface Cultures
Shivani Pathak1,2,3,4, Eric Larson1,2,3,4, Catherine Anderson1,2,3,4, Vijay Ramakrishnan1,2,3,4
1Rocky Mountain Smell and Taste Center, Aurora, CO, United States, 2Department of Otolaryngology, Aurora, CO, United States, 3Department of Developmental and Cell Biology, Aurora, CO, United States, 4University of Colorado School of Medicine, Aurora, CO, United States

Cellular differentiation towards a committed cytotype within the nasal epithelium can go in one of two directions: either towards a secretory or a ciliated cell fate. Solitary chemosensory cells (SCCs) are secretory cells that proliferate throughout the life of the adult animal, similar to the replacement rate of other sensory cells, namely the olfactory sensory neurons and taste cells. These sensory cells originate from basal cells within the epithelial lining that express particular transcription factors. Prior research has shown that SCC activation by bitter compounds or bacterial metabolites triggers trigeminal nerve stimulation resulting in cardinal signs of nasal inflammation including plasma extravasation and mast cell degranulation. SCCs have demonstrated importance in type 2 inflammation, where the chemokine IL-13 is known to induce goblet cell hyperplasia and decreased ciliation. We hypothesize that IL-13 exposure results in SCC proliferation in differentiated cell culture, consistent with its known effect on driving secretory cell fate. We exposed primary human nasal epithelial air-liquid interface (ALI) cultures to IL-13 at 20ng/mL for 2 weeks post differentiation and collected RNA for qualitative polymerase chain reaction. Our results reveal an increase in expression of the SCC markers alpha-gustducin and transient receptor potential cation channel subfamily M member 5 in the exposed group. Similar to previously published data, we also find a decrease in expression of the ciliated cell marker ARL13 and an increase in expression of the goblet cell marker MUC5B. This finding suggests that IL-13 exposure drives differentiation of the airway epithelium towards a secretory cell fate and increases the number of SCCs within the epithelial culture unit.

Innervation Of Taste Buds By Transcriptomically Distinct Gustatory Neurons Of The Geniculate Ganglion
Judith Rosales Rivas1, Gennady Dvoryanchikov1, Nirupa Chaudhari1,2,3
1Department of Physiology & Biophysics, University of Miami Miller School of Medicine, Miami, FL, United States, 2Graduate Program in Neurosciences, University of Miami, Miami, FL, United States, 3Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL, United States

The geniculate ganglion contains three transcriptionally distinct populations of gustatory neurons, T1, T2, and T3. It is not known whether these three neuronal types represent functionally different neurons, or if they innervate anatomically distinct targets. To address this, we used guidance from our previously established markers to identify three transgenic strains, each with one neuronal type fluorescently labeled. Specifically, we visualized T1 peripheral axons using Foxg1-Cre; tdTOM mice. T3 fibers were visualized in Penk-Cre; tdTOM mice. To examine the peripheral targets of fluorescently labeled fibers, we performed immunohistochemistry on oral tissue. In lingual and palatal sections, T1 axons entered taste buds, branched, and were closely apposed to individual taste receptor cells. T3 axons also exhibited an overall similar pattern of association with taste buds and cells. However, our preliminary results suggest that T1 and T3 fibers may preferentially associate with different taste bud cell types (T1 with type II and T3 with type III). Thus, T1 and T3 neurons may represent distinct neural pathways or functions. We also examined T2 peripheral axons, in this case, using Mafb-mCherry mice. Unlike T1 and T3 axons, T2 fibers rarely entered taste buds. Instead, T2 axons approached only a subset of taste buds, exhibited limited branching, and formed varicosities adjacent to the taste bud. We hypothesize that these structures may represent specialization for mechanosensitivity, a property suggested by the transcriptome of T2 neurons.

Receptive Field Size And Somatosensory Responses Of Rat Lingual Nerve/Trigeminal Ganglion Neurons Innervating Fungiform Papillae.
Hajime Sato, Archana Kumari, Charlotte M. Mistretta, Robert M. Bradley
Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan., Ann Arbor, MI, United States

Anterior tongue fungiform papillae are complex sensory organs innervated by both the facial (chorda tympani, CT) and trigeminal nerves (lingual, LN). We have investigated characteristics of the CT/geniculate ganglion (CT/GG) innervation (Yokota & Bradley, 2017) and now report properties of the LN innervation. With extracellular recordings from LN/trigeminal ganglion (LN/TG) neurons in adult rats, receptive field (RF) and sensory response properties were determined by mechanical and thermal stimulation of fungiform papillae. RF size was mapped by mechanically stimulating individual fungiform papillae using a hand held nylon filament and strain gauge. Thermal stimuli were distilled water at 4°C and 25-30°C applied to the anterior tongue via an in-line heater/cooler. Thirty-three single mechanoreceptive LN/TG neurons were isolated. Thirteen were classified as rapidly adapting (RA) and 20 as slowly adapting (SA). RA neuron fields were distributed mainly on the tongue tip and SA fields were across the anterior tongue. The average RF size of RA units was 6±3 fungiform papillae (mean ± SD; range = 2-11) and that of SA units was 3±2 (range = 2-7) papillae. Most RFs (25) were oval-shaped whereas 8 were linearly arranged. A subset of LN/TG mechanoreceptive units also responded to thermal stimulation: 5 SA and 2 RA units responded to cold; 2 SA and 1 RA unit responded to warm. The mechanoreceptive/thermal LN/TG units had a mean RF size of 5±3 fungiform papillae. Overall, LN/TG neurons incorporate a moderate number of fungiform papillae in the RF and respond to touch and temperature. The fungiform papillae in LN/TG neuron fields, together with multimodal CT/GG projections to the papillae, constitute exquisite multisensory lingual organs for initial nutrient discrimination.

Both Form And Function Of Type I Taste Cells Suggest A Role In Taste Signal Transmission And/Or Modulation
Courtney E Wilson1,2, Eric D Larson1, Catherine B Anderson1, Aurelie Vandenbeuch1, Ruibiao Yang2, Thomas E Finger2, Sue C Kinnamon1
1Department of Otolaryngology, University of Colorado School of Medicine, Aurora, CO, United States, 2Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, United States

Type I taste cells are often described as the glial-like support cells of mammalian taste buds. Type I cells wrap around neighboring cells, and likely remove neurotransmitter released by receptor cells. To test whether Type I taste cells might play a role in modulation or transmission of taste information, we examined aspects of Type I morphology and physiology. Using serial EM images of mouse circumvallate taste buds, we observed regions of apparent specialized contact between some Type I cells and nerve fibers. These nerve fibers “nest” in invaginations of these Type I cells, being separated from the nucleus only by the plasma membrane and a thin rim of cytosol. At these contact points, the area between the Type I cell nuclear envelope and the section of outer membrane that abuts the nerve fiber is more electron dense than the surrounding cytoplasm, suggestive of a point of specialized contact. Morphologically, Type I cells, which separate Type II and Type III cells, are well poised to participate in cell-cell communication within the bud. If this is the case, Type I cells should respond to neurotransmitters released by taste receptor cells including ATP which is released by Type II cells. To test whether Type I cells respond to ATP, we used calcium imaging of isolated Type I cells as marked by tdTomato fluorescence driven by a Gad65-Cre construct. Type I cells were identified as fluorescently marked cells that did not show depolarization-evoked calcium influx. These Type I cells did show calcium increases in response to extracellularly applied ATP. These data indicate a more expansive role for Type I cells in the transduction and integration of signals in the mammalian taste bud than has been considered previously.

Unilateral Odor Delivery Evokes Sustained Neural Oscillations In Ipsilateral Piriform Cortex In Humans
G. Nazli Dikecligil1, Nisha Sanghani1, Sandhitsu R. Das1, Joel M. Stein2, Han-Chiao Isaac Chen3, Timothy H. Lucas3, Kathryn Davis1, Jay A. Gottfried1
1Department of Neurology, University of Pennsylvania, Philadelphia, PA, United States, 2Department of Radiology, University of Pennsylvania , Philadelphia, PA, United States, 3Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA, United States

Unlike auditory, visual and somatosensory systems, sensory responses arising in the periphery of the olfactory system predominantly target the primary sensory cortex of the ipsilateral hemisphere. The extent to which contralateral piriform cortex (PC) receives odor related information arising from a unilateral nostril in humans is understudied. To investigate this question, we recorded intracranial EEG signals from the PC of patients with medically resistant epilepsy during their hospital stay. The subjects performed an odor identification task on a computer as stimuli were delivered via a computer controlled olfactometer. Subjects were instructed to sniff following a visual cue and respond to a stimulus identification question following the stimulus sampling period. The stimulus on a given trial was randomly selected from a set of 4 odor and 1 no-odor (air) bottles and delivered either to the left, right or both nostrils. The preliminary findings (n=3 subjects) demonstrated that single nostril odor delivery (but not air delivery) evoked sniff onset aligned oscillations exclusively in the ipsilateral hemisphere. Across all 3 subjects, odor delivery elicited robust, narrow band gamma oscillations (~30-40 Hz) that emerged 750-2000 ms after sniff onset and were sustained (~2s in duration) up to the odor identification question. The late onset, sustained gamma activity may play a role in retaining a representation of the olfactory trace for post-stimulus processing. Furthermore, these preliminary findings suggest that processing of odor information arriving from a unilateral nostril may occur predominantly in the PC ipsilateral to the odor delivery in the human olfactory system. 

Separating Respiration, Trigeminal And Olfactory Effects At The Cortical Level
Florian Fischmeister1, Christina Kumpitsch3, Cinzia Cecchetto1,2, Christine Moissl-Eichinger2,3, Veronika Schöpf1,2
1University of Graz, Graz, *, Austria, 2BioTechMed, Graz, *, Austria, 3Internal Medicine, Graz, *, Austria

Human odor perception is based on the tight interplay between the olfactory and the trigeminal system since most odorants stimulate both systems simultaneously. Additionally, odor perception is modulated by breathing, which also affects neuronal activity. To overcome possible biases in studies using intranasal chemosensory stimulation various experimental schemes using respiration triggering were proposed. Yet, such designs are technically demanding and prone to errors. Here we aim to separate respiration, trigeminal and odorant effects in a pseudo-free breathing paradigm. In this fMRI study, normosmic and hyposmic participants performed simple guided breathing where they had to match their breathing cycle to an expanding or shrinking ball. During the inhale-phase an odor stimulus (rose and peppermint), or diluted CO2 as trigeminal stimulus were presented birhinally using a computer controlled olfactometer. Data were analyzed using a standard GLM with the individual breathing pattern as an additional regressor.  Preliminary results of 5 participants already show that olfactory stimuli activated primary and secondary olfactory regions, while CO2 activated somatosensory regions and breathing the basal ganglia, cerebellum, and frontal areas. Direct comparison of odor versus breathing exhibited stronger and more distinct activation within both piriform cortices as well as within the parahippocampal and entorhinal cortices, both not found in the direct contrast. In hyposmic participants, a similar pattern evolved at a very lean threshold. CO2 compared to breathing revealed strong activation within the insular cortex and the supramarginal gyrus in both groups. These results further previous literature and emphasize the importance of the tight control of respiration pattern in olfactory science.

The Influence Of Α-Synuclein Seeding In The Olfactory Bulb On Olfactory Functional Connectivity
Aishwarya S. Kulkarni1, Heather B. Denson1, Gabriela Mercado Guerra2, Maria del mar Cortijo1, Jennifer A. Steiner2, Patrik Brundin2, Daniel W. Wesson1
1Univ of Florida, Dept of Pharmacology & Therapeutics, Center for Smell and Taste, Gainesville, FL, United States, 2Van Andel Research Institute, Grand Rapids, MI, United States

Parkinson’s disease (PD) is a prevalent neurodegenerative disorder which results in debilitating symptoms ranging from cognitive impairments, loss of motor function, and also olfactory impairments. α-synuclein, which aggregates into Lewy bodies, is implicated in PD onset and its progression. Interestingly, α-synuclein is observed in the olfactory bulb (OB) early during PD pathogenesis, leading us to predict that α-synuclein aggregation may underly olfactory impairments in PD. Indeed, α-synuclein seeded into the OB of mice entails age-dependent loss of odor-guided behavior. Based upon the above, we sought to test the specific hypothesis that OB α-synuclein seeding impairs the network dynamics within the OB and piriform cortex (PCX), as well their functional connectivity. To study this, we seeded α-synuclein fibrils or a vehicle control into the OB of mice and following several weeks to allow for aggregation, implanted bipolar electrodes ipsilaterally in the OB and PCX. Subsequently, spontaneous and odor-evoked local field potential (LFPs) activity were recorded from the mice while they were awake. In our initial analyses, we have adopted Fast Fourier Transform analysis to quantify the modulation of LFPs in the presence and absence of olfactory inputs. Further, we have begun to examine spontaneous and odor-evoked functional coherence between the OB and PCX. These findings will give us an insight into the impact of α-synuclein on olfactory neural activity, including LFPs. Future efforts will determine the impact of α-synuclein on the representation of odors and how this may change during pathological progression.

Respiration Induces Phase Synchronization Of Olfactory-Hippocampal Networks In Humans
Gregory Lane, Guangyu Zhou, Stephan Schuele, Joshua Rosenow, Christina Zelano
Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States

The olfactory system is an important alerting system that detects life-endangering stimuli in rodents as well as in humans. In real life situations, the perception of a smell can come to awareness without active sniffing, which suggests that olfactory brain areas monitor the contents of ongoing autonomic breaths. Previous studies have demonstrated that natural nasal breathing entrains local field potential oscillations in both olfactory and non-olfactory brain regions. Furthermore, odor stimulation can also induce phase synchronization between piriform cortex and hippocampus. Whether this synchronization occurs during natural breathing, in the absence of odor, is unknown. Given the role of the hippocampus in memory encoding during ongoing sensory sampling, we hypothesized that natural breathing could modulate its coupling with primary olfactory regions, such as piriform cortex. In this study, we used intracranial EEG methods to record fifteen minutes of resting local field potential data from eight epilepsy patients. We examined functional connectivity between piriform cortex and hippocampus using inter-trial phase locking value (PLV). We found rhythmic modulations in coupling between piriform cortex and hippocampus occurring in phase with natural breathing such that low frequency PLV (1–8 Hz) increased following inhalation and decreased during exhalation. This finding suggests that resting-state coupling between piriform cortex and hippocampus is tied to the natural respiratory cycle, which might be an energy-efficient, subconscious implementation of the olfactory alerting system.

Neural Dynamics In The Developing Piriform Cortex Of Awake Rats
Zihao Zhang, D. Chad Collins, Joost X. Maier
Wake Forest School of Medicine, Winston-Salem, NC, United States

Revealing the mystery of cortical development can help us understand how cortical circuits learn to process information. Recent work on the visual and somatosensory systems has shown that cortex learns to process information during the pre-critical period, mostly in the absence of sensory input. For example, before maturation of the retina, spontaneous retinal waves trigger 10 Hz spindle oscillations in the thalamocortical loop that drive plastic changes in visual cortex. Little is known about the development of piriform olfactory cortex—a three-layer paleocortex that lacks thalamic relay and receives natural sensory input from birth. Here, we ask whether the same activity patterns observed during development of neocortex are observed in piriform cortex by recording local field potential (LFP) activity in piriform cortex of awake rats during the first three weeks of life (P0-21). Rat pups were head-fixed and actively sampled orthonasal amyl acetate. Respiration was recorded with a pressure sensor. At birth, the piriform LFP exhibits respiration and spindle oscillations in response to odor stimuli. Beta oscillations increase in frequency until they reach adult values by P12. “Gamma” oscillations were transiently expressed between P5 and 12. In parallel, spontaneous activity undergoes a dramatic increase in structure. These developmental dynamics appeared to be aligned with the emergence of exploratory sniffing behaviors. These findings indicate that early developmental dynamics observed in piriform cortex activity are highly similar to those previously observed in neocortical sensory areas. This suggests that the principles underlying cortical development are evolutionarily conserved, and that sensory cortical development may be coordinated across the brain.  

Roux-En-Y Gastric Bypass Surgery Influences Intake And Preference Of Glucose Solutions With No Effects On Concentration-Dependent Licking In Brief Access Tests In Female Rats.
Kellie M. Hyde1, Marco Bueter2, Carel W. le Roux3, Alan C. Spector1
1Florida State University, Tallahassee, FL, United States, 2University of Zurich, Zurich, *, Switzerland, 3University of College Dublin, Dublin, *, Ireland

We tested the effect of Roux-en-Y gastric bypass (RYGB) on long-term intake and preference of glucose solutions and the influence of this stimulus exposure on concentration-dependent licking in brief access (BA) tests. Female Sprague-Dawley rats, receiving either RYGB (n=13) or sham surgery SHAM (n=11), were allowed 23-h access to 0.6M glucose and water in 5 consecutive, 46-h two-bottle tests (TBTs). RYGB lowered intake of 0.6M glucose (p=0.01) without changing glucose preference (p=0.97) relative to SHAM. Glucose concentration was increased (2.0M) for a second series of TBTs during which RYGB rats maintained lower glucose intake and increased water intake, resulting in a decrease in 2.0M glucose preference, relative to the SHAM group (all p’s≤0.003). Finally, rats received 0.6M glucose again in two TBTs and, similar to the first exposure, RYGB rats drank less glucose than the SHAM rats and preference did not significantly differ between the groups. Additionally, before and after the initial series of 0.6M glucose TBTs, and after 2.0M glucose TBTs, rats were tested in 30-min BA tests (10-s trials) to an array of glucose concentrations (0, 0.06 – 2.0M) while nondeprived. Despite the decreased long-term intake (0.6 & 2.0M) and preference (2.0M) to glucose, RYGB did not significantly impact concentration-dependent licking during the BA tests but did decrease the number of trials initiated (p=0.001) relative to SHAM. Overall, we speculate that RYGB causes early satiation of glucose intake and at high concentrations, increases water intake to potentially attenuate the effects of the colligative/caloric load. None of these outcomes are associated with RYGB-induced decreases in the orosensory motivational potency of glucose to drive concentration-dependent licking even after repeated long-term exposure.

Interaction Of Taste And Smell On Perception Of Sweetness In Honey Bees
Allyson V. Pel, Stephanie R. Hathaway, Susan E. Fahrbach
Department of Biology, Wake Forest University, Winston-Salem, NC, United States

Perception of sweetness depends on sugar content of foods, but organic volatiles produced by certain fruits result in an overestimation of sweetness by humans. It is unknown if this phenomenon occurs in other species. This project focuses on how the interaction of smell and taste modulate perception of sweetness in honey bees (Apis mellifera). Honey bees are generalist foragers that forage for nectar of varying sweetness at different flowering plants; it is well-documented that they readily discriminate different concentrations of sucrose and show a strong preference for higher concentrations. Honey bees also experience floral odors as they forage, creating the possibility that the combination of taste and odor might modulate perception of sweetness. Linalool, geraniol, and 6-methyl-5-hepten-2-ol were used as odorants that may enhance the perception of sweetness by honey bees found in some of the flowering plants honey bees forage upon; limonene and no odorant were used as controls. Bees were tested using proboscis extension response (PER) laboratory assays and gustatory acceptance score (GAS) field assays. In the PER assays, only geraniol enhanced sweetness perception in honey bees compared with the limonene and no odor treatments. By contrast, there was no difference in responses to any compounds in the field studies. In the laboratory, the effect of these odorants on sweetness perception was age-dependent. To our knowledge, this is the first demonstration of the modulation of the perception of sweetness in an insect by simultaneous olfactory input.

Role Of The Carbonate Ion In The Enhanced Avoidance Of Sodium And Potassium Salts In Rats
Steven J. St. John
Rollins College, Winter Park, FL, United States

As noted decades ago by Morrison (e.g., Morrison, 1969), sodium carbonate is apparently considerably saltier to rats than anticipated based on its chemistry as a divalent salt.  Morrison showed that, compared to NaCl, rats behaviorally avoid sodium carbonate at 10-fold lower concentrations, but also that they will prefer sodium carbonate at 10-fold lower concentrations when sodium deplete (Morrison & Young, 1972).  Our lab has replicated this finding (St. John, 2017).  These results suggests that the saltiness of sodium carbonate is potentiated, rather than that sodium carbonate contains a non-salty aversive quality as it does in humans.  Sodium carbonate is a strong base (pH around 10.5).  In order to examine the roles of the cation, anion, and pH on the potentiated responses to sodium carbonate, we presented thirsty rats (N = 16) with concentration series of NaCl, KCl, sodium carbonate, potassium carbonate, and NaCl to which a small amount (0.005 M) of sodium carbonate was added, sufficient to increase the pH of the solutions (pH range: 9.8-10.0).  Behavioral sessions consisted of one series only (10 s trials, randomized block design), but over 5 weeks rats were presented with each series in 4 different test sessions (M = 19.6 trials/concentration).  Consistent with previous work, both sodium carbonate and potassium carbonate were more than twice as aversive than their chloride salt counterparts.  The pH modification of the NaCl series had no effect.  Thus, the enhanced saltiness of carbonate solutions appears to be dependent on the anion, although the inability to control the intraoral pH of the solutions limits the strength of this conclusion.

Odor Valence Encoding Among Dopamine Receptor Expressing Medium Spiny Neurons
Lucas A. Stetzik, Daniel W. Wesson
Dept. of Pharmacology and Therapeutics, Center for Smell and Taste, University of Florida, Gainesville, FL, United States

The valence of an odor is encoded in the brain to help direct an animal’s behavior toward reinforcing stimuli and away from noxious stimuli. The olfactory tubercle (OT) is a region of the ventral striatum which we have reported encodes odor valence through changes in neural firing rates. To expand upon this finding, herein we sought to identify the neuronal population underlying this effect, being either medium spiny neurons expressing the D1 or D2 type dopamine receptor (D1-MSN, D2-MSN) – the principal neuron types in the OT. We achieved this using fiber photometry to record GCaMP6f fluorescence in populations of D1- and D2-MSNs, from the OT of mice engaged in a lick/no-lick odor discrimination and reversal learning task. Our reversal learning results reveal that in the OT, conditioned rewarded, but not unrewarded, odors selectively increase D1-MSN activity to differentially encode odor valence and not odor identity.  While D2-MSNs did respond to both conditioned and unconditioned odors, the reversal results indicate that odor valence was not encoded among these neurons. This project supports previous work from our lab showing that the OT encodes odor valence, and builds upon on this finding by uncovering the neuronal populations underlying this effect.

The Influence Of Expertise On The Multisensory Imagery Of Wine
Ilja Croijmans1, Laura J. Speed2, Artin Arshamian3, Asifa Majid2
1Utrecht University, Utrecht, *, Netherlands, 2University of York, York, *, United Kingdom, 3Karolinska Institutet, Stockholm, *, Sweden

Taste and smell seem hard to imagine, but people differ in this ability. Yet, the mechanisms by which people differ have been underexplored. Here we investigate whether one such mechanism is expertise. Wine is a multisensory experience, combining information from vision, taste, and smell; and wine experts learn their skills in this domain. Is wine imagery improved in expertise, and if so is this trait learnt or are they better imagers in the first place? If better chemosensory imagers become experts then their imagery ability should not improve over time. To investigate this, we first compared a group of 66 wine experts to 66 yoked novices using the newly developed Vividness of Wine Imagery Questionnaire (VWIQ) measuring wine imagery in the modalities vision, taste and smell. Overall, wine experts had greater vividness of wine imagery compared to novices, F(1, 130) = 28.90, p <.001. The interaction between expertise and modality, F(2, 260) = 5.20, p = .009, revealed that experts did not differ in  vividness across modalities, whereas novices had more vivid visual than taste or odor imagery. Next, we followed 20 students from the Dutch Wine Academy and a group of 45 control participants. Participants completed the VWIQ at two time points; students completed the questionnaire before and after six months of weekly day-long wine classes. Students and controls did not differ before the course, but after the course students reported more vivid wine imagery, F (1, 55) = 8.35, p = .006. Overall, we show having vivid chemosensory imagery is not critical to become a wine expert, but that this ability can be trained. We provide strong evidence that expertise improves imagery, exemplifying the extent of its plasticity in cognition for the chemical senses.

Ofc Inactivation Disrupts Economic Choice Behavior Following Devaluation Of An Appetitive Stimulus.
Matthew P Gardner1, Jessica C Conroy1, Davied Sanchez1, Geoffrey Schoenbaum1,2,3
1National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, United States, 2Departments of Anatomy & Neurobiology and Psychiatry, University of Maryland School of Medicine, Baltimore, MD, United States, 3Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University, Baltimore, MD, United States

How humans and animals choose between chemosensory distinct foods remains a critical question in neuroscience. There has been considerable evidence that the orbitofrontal cortex (OFC) is necessary for choice behavior when the value of an offered food must be integrated across multiple dimensions of appetitive stimulus features. We have previously demonstrated that rats performing an economic choice task, in which rats decide between biologically relevant appetitive stimuli which vary across features of food-type and size, are completely unaffected by inactivation of the lateral portion of the OFC during the choice period of the task. This showed that lateral OFC is not necessary for well-learned economic choice behavior. Yet this inactivation was done when the appetitive reinforcers had relatively stable values over time. Here we devalued one of the food pellets using sensory-specific satiety - we pre-fed one of the food-types prior to starting a session - and tested whether shifts in preference away from the sated food were dependent on OFC function. We found that the normally observed shifts in preference following sensory-specific satiety were abolished by OFC inactivation. This is consistent with the hypothesis that OFC is necessary for tracking expectations of specific appetitive stimuli during choice behavior. Furthermore, this dependence on OFC only becomes apparent when up-to-date knowledge of an expected appetitive stimulus is necessary for the current choice. 

Flavor Experience Induces Plastic Changes In Piriform Cortical Coding Of Odor Valence
Joost Maier, Ellen Walker
Wake Forest School of Medicine, Winston Salem, NC, United States

Most of our experience of the chemosensory world is heavily shaped by individual experience. This is reflected in the anatomical organization of piriform olfactory cortex, which is characterized by diffuse afferent inputs from the olfactory bulb and a high degree of intra- and inter-cortical associative connectivity. However, odor coding by piriform cortical neurons is often studied in the absence of experience or context. Here, we probed rats with natural flavor stimuli in the context of a preference learning task to study how experience and connectivity with extra-olfactory systems drives plastic changes in cortical coding of odor valence. We tested preference for two odorant solutions before and after rats were trained to associate one of the odorants with sweet taste (saccharin). In parallel, we recorded extracellular responses of OC neurons to intra-oral presentation of the same odors. We found that training increased preference for sweet-paired odors, and that this increase in preference was correlated on an animal-by animal basis with an increased ability to decode odors from ensembles of OC neurons. At the cellular level, altered representations were implemented by a complex combination of increases and decreases in the firing rate of individual OC neurons. Odor- and valence-related responses varied dynamically over the course of several seconds following stimulus delivery. These results demonstrate that multisensory input drives experience-dependent plasticity in odor valence representations by altering spatio-temporal dynamics of piriform cortical activity. Ongoing work focuses on contrasting plastic changes that support preference and aversion learning, as well as probing a causal role for taste cortex in mediating plasticity in odor coding.

Rats Fail To Discriminate Between Quinine And Other Bitter Taste Stimuli
Laura Martin, Kristen Kay, Kimberly James, Ann-Marie Torregrossa
SUNY University at Buffalo, Buffalo, NY, United States

There is evidence that each of the approximately 30 bitter receptors responds selectively to distinct bitter stimuli, however Spector and Kopka (2002) demonstrated that rats cannot discriminate quinine from denatonium, suggesting that rats perceive these bitters as identical. More recent work by Meyerhof et al (2010) has demonstrated that quinine and denatonium activate similar patterns of TAS2R cells. Electrophysiological recordings in both the mouse (Wilson et al, 2012) and rat (Geran and Travers, 2006) NTS also suggest that quinine and denatonium generate similar neural responses, lending support to the behavioral findings. However, other bitter stimuli, such as cycloheximide, appear to generate neural responses distinct from quinine. With the same modified forced choice task used in Spector and Kopka, we compared quinine to a range of bitter stimuli (denatonium, cycloheximide, PROP, and SOA). Rats were asked to discriminate between two solutions, with multiple concentrations of each solution tested simultaneously, so rats could not discriminate based on intensity of the stimulus. We replicated the findings of Spector and Kopka, as our rats could not discriminate quinine from denatonium (51.1 ± 0.55% correct, 50%= chance performance). We further demonstrated that rats were unable to discriminate quinine from cycloheximide (48.6 ± 0.71% correct) or PROP (52.1 ± 0.59% correct). Rats showed a weak ability to discriminate between quinine and SOA (61.3 ± 1.69% correct). All animals were able to discriminate quinine from KCl (88.3 ± 0.86% correct), which demonstrates that they were capable of completing the task. These data lend support to the conclusion that bitter stimuli are indistinguishable.

Is Camkii-Α Important For Olfactory Learning And Working Memory?
Daniel Ramirez-Gordillo, K. Ulrich Bayer, Amber Olson, Diego Restrepo
University of Colorado Anschutz Medical Campus, Aurora, CO, United States

Mutations to the α-isoform of calcium/calmodulin-dependent protein kinase II (CaMKII-α) are associated with an increased risk of developing a schizophrenia, a neuropsychiatric disorder characterized by impaired concentration, working memory, perception and social dysfunction. CaMKII-α is highly expressed in the brain including the hippocampus and prefrontal cortex, two areas of the brain important for learning and memory.  CaMKII-α is important for long term potentiation (synaptic plasticity) and memory. Heterozygous CaMKII-α knockout mice (Het) have been described to show a schizophrenia-related phenotype including immature dentate gyrus (DG), hyperactivity, working memory deficits, and social withdrawal. Finally, CaMKII-α is expressed in the granule cells of the olfactory bulb. However, the role of CaMKII-α in olfactory learning is not well understood. To further investigate the role of CaMKII-α in schizophrenia, we used a go-no go olfactory discrimination task and an olfactory working memory task to assess cognitive learning deficits and awake behaving tetrode recording to measure neuronal oscillations in the hippocampus and prefrontal cortex. Mice learned to associate an odorant with a water reward in the go-no go task. Mice received double tetrode implants aimed at the CA1 region of the hippocampus and medial prefrontal cortex. All mice learned to differentiate between dissimilar odors. However, when the odor pair was similar and was reversed, Het mice took longer to learn the task. Furthermore, there was an increase in activity for the rewarded odorant in the prefrontal cortex and hippocampus. These observations suggest a key role of CAMKII in associative odorant learning. 

Sodium, But Not Potassium, Blocks Bitterness In Simple Model Chicken Broths
Paul M Wise1, Shashwat Damani3, Paul AS Bresline1,2
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2Rutgers Univerisity, New Brunswick, NJ, United States, 3Lactalis American Group, Inc., Buffalo, NY, United States

Potassium chloride (KCl) has proven useful as a salty taste replacer to help reduce dietary sodium. KCl, however, fails to replace other important sensory modulatory effects of sodium. For example, in simple, aqueous solutions sodium blocks the perception of bitterness of selected compounds, whereas KCl does not. We tested the ability of potassium to block bitterness in a more complex food by presenting model chicken broths to healthy adults. Broths were presented in three added salt conditions: 1) no added salt, 2) salted with NaCl, or 3) salted with KCl. To create a model bitter off-taste, four concentrations of L-tryptophan (present in chicken meat) were added to each broth. In Experiment 1, the base broth consisted of chicken flavor only. In Experiment 2, the base broth was more complex, containing savory (umami) ingredients. Data were analysed using ANOVA models. In both experiments, subjects rated broths with either added NaCl or KCl as significantly saltier than unsalted broths. Only NaCl, however, significantly suppressed the rated bitterness of broths (by about 30%, across a wide range of L-tryptophan concentrations). Accordingly, when complex foods have sodium reduced and potassium increased to balance salty taste, the sensory modulating properties of sodium will need to be replaced independently, since potassium does not share these traits.

Mice Can Condition Cephalic-Phase Insulin Release To The Taste Of Maltodextrin, But Not Saccharin Or Sucrose
Alyson Dennis1, Lillian R. Brouwer1, Anthony Sclafani2, John I. Glendinning1
1Barnard College, Columbia University, New York, NY, United States, 2Brooklyn College of City University of New York, New York, NY, United States

Oral stimulation with glucose elicits insulin release in mice by activating KATP channels (not T1R2+T1R3 receptors) in taste cells. This cephalic-phase insulin release (CPIR) is beneficial because it attenuates the rise in blood glucose during and after meals. Glucose-containing saccharides can also elicit CPIR once the glucose molecule has been liberated by enzymes (amylases and alpha-glucosidases) in the mouth. We asked whether C57BL/6 mice could learn to generate a CPIR in response to tastants that do not normally elicit CPIR—i.e., saccharin, or glucose-containing saccharides mixed with acarbose (an inhibitor of amylases and alpha-glucosidases). During conditioning, we paired a tastant with oral and/or postoral glucose across five 1-hr/day sessions. During CPIR testing, we measured immediate changes in plasma insulin after mice completed 200 licks for a tastant, in the absence of glucose. In Experiment 1, mice ingested 10 mM saccharin while 1 M glucose was co-infused via an implanted intragastric catheter. However, this procedure failed to condition CPIR to 10 mM saccharin during testing. In Experiment 2, mice ingested a mixture of 10 mM saccharin + 1 M glucose during conditioning, but failed show a CPIR to 10 mM saccharin during testing. In Experiment 3, mice ingested 1 M sucrose during conditioning, but did not display a CPIR to 1 M sucrose + 5 mM acarbose during testing. In Experiment 4, mice ingested 32% maltodextrin during conditioning, and displayed a small but significant CPIR to 32% maltodextrin + 5 mM acarbose during testing. Our results indicate that mice condition a CPIR to the T1R2+T1R3-independent taste of maltodextrin, but not to the T1R2+T1R3-dependent taste of sucrose and saccharin. More work is needed to explain the taste receptor selectivity of the conditioning process.

Single-Unit Responses To The Intraoral Delivery Of Chemosensory Stimuli In The Mediodorsal Thalamus
Kelly E. Fredericksen, Kelsey A. McQueen, Chad L. Samuelsen
University of Louisville, Louisville, KY, United States

The mediodorsal thalamus (MD) is a secondary thalamic region involved in sensory perception, value, and choice. This region receives input from the chemosensory cortical areas for smell and taste, piriform cortex and gustatory cortex respectively. MD plays a key role in communicating behaviorally relevant chemosensory information, including the hedonic (pleasantness/unpleasantness) perception of flavor, to guide food-related behaviors. The perception of flavor depends upon the multisensory integration of odor and taste. How neurons within MD respond to odors, tastes, and odor-taste mixtures remains unclear. To determine how individual neurons in MD respond to odors, tastes, and odor-taste mixtures, rats were first given repeated experience with a pleasant odor-taste mixture (isoamyl acetate-sucrose; IA-S), and an unpleasant mixture (benzaldehyde-citric acid; B-CA). Then, single-unit neural activity in MD was recorded in awake behaving rats during the intraoral delivery of individual odors, tastes, and odor-taste mixtures. To determine how neurons in MD represent the congruence of odor-taste mixtures, we delivered both previously experienced odor-taste mixtures (congruent; IA-S & B-CA) and mismatched pairings of those mixtures (incongruent; IA-CA & B-S). Our preliminary experiments showthat most of the chemoresponsive neurons in MD respond to all stimulus types, with responses to odor-taste mixtures differing from those evoked by the odor or taste component alone. Future analyses will examine how chemoresponsive neurons in MD represent congruency and hedonic value of odors, tastes, and odor-taste mixtures.

Olfactory And Gustatory Integration At The Earliest Stage Of Sensory Processing In The Drosophila Larva Brain
Jess Kanwal1, James Truman2, Ben de Bivort1, Aravi Samuel1
1Harvard University, Cambridge, MA, United States, 2University of Washington, Friday Harbor, WA, United States

The brain integrates information from different sensory modalities in order to enhance detection and perception of external stimuli and to respond in the most efficient manner. For a Drosophila larva, this means detecting chemosensory cues to locate the most nutritious food source in its environment. How the larva modifies its behavior and how its brain integrates olfactory and gustatory cues in the context of food search remain unknown. To assess the larva’s chemosensory integration behavioral strategy, we compared its behavior along either an attractive olfactory (acetal) or gustatory (fructose) gradient alone to that along simultaneous presentations of both gradients either in parallel or in opposition. Larvae show subadditive enhancement in their ability to orient (heading direction over time) towards the most attractive region of their chemosensory environment when navigating along both gradients in parallel. Neither modality gates the other, as larvae tend to stay near the center of both gradients when they are placed in opposition. We found that silencing specific local interneurons (LNs) or projection neurons (PNs) in the antennal lobe (AL), the first olfactory processing center of the larval brain, modulates the degree of multisensory enhancement. We then used a microfluidics chip to stimulate the chemosensory organs of intact, awake larvae while performing in vivo calcium imaging of the AL neurons. Several LNs and PNs respond to increasing fructose concentrations. Furthermore, one LN reduces its response amplitude when presentations of acetal mixed with increasing concentrations of fructose are delivered. Our data support the idea that multisensory integration occurs at early levels of sensory processing and begin to address how this convergence enhances perception and foraging behavior.

Detecting Taste And Temperature In The Geniculate Ganglion
Sara C.M. Leijon, Guennadi Dvoryanchikov, Lauren C. Baker, Nirupa Chaudhari, Stephen D. Roper
Miller School of Medicine, University of Miami, Miami, FL, United States

Single cell transcriptome analyses (Dvoryanchikov et al 2017) have shown that mouse geniculate ganglion sensory neurons that innervate taste buds form at least three major groups—T1, T2, and T3.  We have been exploring the functional correlates of these 3 groups.  For instance, temperature is an important aspect to the taste of foods and beverages and geniculate ganglion neurons have been shown to respond to thermal stimulation (e.g., Lundy & Contreras 1999, Breza et al 2006, Lu et al 2016, Yokota & Bradley 2016).  Here, we used in vivo Ca2+ imaging (Baretto et al 2015, Wu et al 2015) and post hoc immunostaining to investigate how taste and temperature interact in the geniculate ganglion and whether any of the T1-T3 ganglion neuron groups is selectively sensitive to thermal and/or taste stimulation.  In preliminary experiments (6 mice, 164 neurons) testing oral stimulation, 93 neurons responded only to taste stimuli, 9 only to temperature, and 62 to both taste and temperature.  The total number of cold- and warm-sensitive neurons was similar (34 and 45 neurons, respectively).  Interestingly, our data suggest that warm-sensitive neurons (as opposed to cool-sensitive ones) are significantly likely to also respond to taste stimulation, especially to bitter (Χ2, p<0.0001).  By fixing and immunostaining ganglia for the transcription factor Foxg1 (a marker for T1 neurons) after imaging responses, we found that T1 neurons were taste-responsive and more specifically, over-represented among sucrose “specialist” neurons.  Preliminary findings have not revealed a particular thermal sensitivity in T1 neurons.  Thus far, T2 and T3 neurons remain to be characterized for thermal and taste sensitivity.

Oral Somatosensory Coding Relevant To Flavor By Mouse Trigeminothalamic Tract Neurons
Jinrong Li, Christian Lemon
University of Oklahoma, Norman, OK, United States

Trigeminal subnucleus caudalis (Vc) neurons projecting to the forebrain are implicated to contribute to somatosensory features of flavor but are poorly characterized. Here, we examined oral somatosensory coding by trigeminothalamic tract (VcTT) neurons using extracellular recordings in anesthetized C57BL/6J mice under oral adaptation to 35°C. Orally-delivered stimuli included 7 temperatures (oral ~8°, 14°, 22°, 28°, 35°, 46° and 57°C) and chemesthetic stimuli associated with spice including 1.28 mM menthol (cooling agent, agonist of TRPM8), 1 mM mustard oil (TRPA1) and 1mM capsaicin (TRPV1). Vc cells were classified as VcTT neurons when they met standard criteria for antidromic activation (stable latency; ability to follow high frequency train; collision test) during electrical stimulation of the contralateral thalamus. Eight of 25 thermal-sensitive Vc neurons were identified as VcTT cells. VcTT neurons recorded thus far displayed sensitivity to cooling but were insensitive to noxious hot temperatures, mustard oil, and capsaicin. Cluster analysis revealed VcTT neurons composed 3 groups based on their cooling profiles, with neurons displaying varying selectivity to innocuous cooling (groups 1 and 2) or broad responsiveness to extreme (including noxious) cold temperatures (group 3). Multivariate analysis suggested activity across these groups could allow VcTT neurons to systematically signal differences among temperatures. Furthermore, only 2 cooling-responsive VcTT neurons displayed significant sensitivity to the TRPM8 agonist and cooling agent menthol, suggesting non-TRPM8 mechanisms contribute to oral cooling signals processed along the trigeminothalamic tract. These data begin to delineate the role of VcTT neurons in somatosensory coding relevant to flavor.

State-Dependent Olfactory Information Processing
Mary R Schreck1, Liujing Zhuang1, Andrew H Moberly1, Kate A White2, Daniel W Wesson2, Minghong Ma1
1University of Pennsylvania, Philadelphia, PA, United States, 2University of Florida, Gainesville, FL, United States

In many animals, including humans, external stimuli typically lead to sensory perception during wakefulness, but not during sleep. Such state-dependent gating of information flow likely involves the thalamus for most sensory modalities; however, olfactory information, originated in olfactory sensory neurons (OSNs) and transmitted to the olfactory bulb, can reach the olfactory cortices such as the piriform cortex and subsequently the orbitofrontal cortex without the relay of the thalamus. Previous studies suggest that olfactory gating occurs in the piriform cortex as odor-evoked responses are reduced during the anesthesia-induced slow-wave state or natural sleep, but interpretation of these studies may be confounded by either the use of anesthesia or different odor stimulations due to state-dependent changes in breathing patterns. To ensure consistent peripheral inputs under different brain states, we used an optogenetic approach by expressing channelrhodopsin-2 (ChR2) in all mature mouse OSNs (OMP-ChR2) or a subset of OSNs (M72-ChR2). We optically stimulated these neurons while recording local field potentials (LFPs) and single-unit activities from olfactory areas in freely behaving mice that naturally switch between brain states. In contrast to previous studies, we surprisingly found similar (M72-ChR2, n=5 mice) or larger (OMP-ChR2, n=10) stimulation-evoked responses in the piriform and orbitofrontal cortices during the sleep state compared to the wake state. We are testing the hypothesis that the larger responses during sleep are due to reduced cortical feedback and thus reduced local inhibition. These findings suggest that rather than reduced information flow into the olfactory cortex, the lack of smell perception during sleep is likely due to other mechanisms.  

The Logic Of Olfactory Bulb Outputs Revealed By High-Throughput Single-Neuron Projection Mapping Using Sequencing
Yushu Chen, Xiaoyin Chen, Justus M. Kebschull, Alexei Koulakov, Anthony M. Zador, Dinu F. Albeanu
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, United States

The olfactory bulb relays information about odor objects represented by olfactory sensory neurons through its output neurons, the mitral and tufted (M/T) cells, to higher brain areas. These areas have been proposed to perform distinct functions ranging from odor detection and localization, guiding spatial navigation to odor identification and innate, or learned, stimulus value assignment. Understanding the logic of information flow from the bulb to the rest of the brain is crucial for unraveling the computations performed by olfactory circuits. Current state-of-the-art microscopy-based neuroanatomy is limited in throughput, and therefore difficult to scale up for robust statistical analysis of neuronal projections at cellular resolution. Using MAPseq, a novel high-throughput method for mapping single-neuron projections via barcode sequencing, we investigated the single-cell projection patterns of 1,466 mitral and tufted cells (3 mice). Our data recapitulates the distinct, but distributed projection patterns of M/T cells previously observed using single-neuron tracing. Furthermore, we identified structured modules of projections from mitral cells to distinct domains along the anterior-posterior axis of the piriform cortex. These modular structures contained well-defined collaterals to non-piriform areas, and were reproducible across animals. Our results indicate that information flows from the bulb to higher brain areas in a structured, non-random fashion. Currently, we further examine the spatial distribution of mitral and tufted cells with specific projection modules using a combination of laser capture microdissection and in situ barcode sequencing.

Role Of The Ciliary Enriched G-Protein Coupled Receptor, Mchr1, In Olfactory Signaling
Kalene R Jasso1,2, Jordan M Ross3, Heather Kulaga4, Max L Fletcher 3, Randall R Reed 4, Jeremy C McIntyre1,2
1University of Florida Department of Neuroscience, Gainesville , FL, United States, 2University of Florida Center for Smell and Taste, Gainesville , FL, United States, 3University of Tennessee Health Science Center, Department of Anatomy and Neurobiology, Memphis , TN, United States, 4Johns Hopkins University , Baltimore, MD, United States

Melanin concentrating hormone (MCH) is a neuropeptide synthesized by neurons in the lateral hypothalamus (LH) that send projections throughout the brain to numerous areas including the olfactory bulb (OB), piriform cortex and olfactory tubercle. MCH has been shown to contribute to the regulation of several chemosensory behaviors, such as feeding and arousal. In rodents, the receptor for MCH is melanin concentrating hormone receptor 1 (MCHR1) a g-protein coupled receptor enriched in the primary cilium. The primary cilium is a conserved organelle that functions as a signaling center projecting from nearly every cell type including neurons. Using both immunohistochemistry and a novel CRISPR/CAS9 mCherry:MCHR1 mouse we have detailed the localization of MCHR1 in the OB. With both methods we find that MCHR1 localizes to the primary cilium of granule cells and a subset of glomerular interneurons, including tyrosine hydroxylase positive cells. MCHR1 is not detected in the primary cilia of mitral cells. To test the role of MCHR1 in olfactory signaling, we have performed behavioral and functional imaging experiments. Using a food finding paradigm, MCHR1 knockout mice are significantly faster at finding a buried a food pellet than wildtype littermates (n =10KO, 8WT. p <0.01 students’ t-test). Using epifluorescence imaging of the dorsal surface of the OB, we find that glomerular responses are enhanced following administration of an MCHR1 antagonist (t(157) = 5.425, p <0.0001). Together these data suggest that MCH/MCHR1 signaling contributes to modulation of olfactory function. Further our newly generated mouse line will aid in studying the role of MCHR1 in other chemosensory areas and will aid in determining the importance of ciliary localization of MCHR1 in modulating olfactory behaviors.

Significant Delay Between Nasal Thermocouple Respiratory Measurements And The Strongly Coherent Olfactory Bulb Respiratory Rhythm
Leslie M Kay1,2
1Department of Psychology, University of Chicago, Chicago, IL, United States, 2Institute for Mind and Biology, University of Chicago, Chicago, IL, United States

Many experiments in rodent olfactory neurophysiology rely on concurrently measured respiratory signals in the nasal cavity. It is assumed that the respiratory rhythm measured in the nose is synchronous with respiratory drive in the olfactory bulb (OB) network. The present study analyzes time delays between the respiratory signals in the nose and the OB local field potential (LFP). Results show that 1) the OB LFP low frequency activity (3-12 Hz) is strongly coherent with nasal airflow as measured with a thermocouple, and 2) there is a consistent delay of approximately 70 msec from the nose to the OB signal. The delay is only slightly shorter than that previously calculated between the diaphragm EMG activity and the OB LFP respiratory rhythm (~80 msec). While there is some variance in delay across OB locations and subjects, individual delays are quite robust. Accounting for the delay measured at a particular OB location provides for better locking of fast LFP oscillations in the gamma and beta range to the respiratory rhythm due to the non-sinusoidal and variable frequency of the respiratory rhythm. These results suggest that prior studies that examine single neurons recorded in the OB relative to respiratory phase as measured in the nose may not have accurate measures of respiratory phase and may in fact underestimate respiratory locked activity. The OB LFP respiratory rhythm provides better access to the brain’s representation of the rhythm than airflow in the nose.

Trpm5-Expressing Microvillous Cell-Dependent Regional Adaptive Plasticity In The Mouse Olfactory Epithelium And Bulb During Environmental Chemical Challenge
Kayla Lemons, Weihong Lin
University of Maryland Baltimore County, Baltimore, MD, United States

Exposure to inhaled irritating and harmful chemical substances can adversely impact the structure and function of the main olfactory epithelium (MOE), and subsequently, the main olfactory bulb (MOB), which receives axonal projections from the MOE. We previously demonstrated that transient receptor potential channel M5-expressing microvillous cells (TRPM5-MCs) in the MOE play an important role in maintaining odor-evoked electroolfactogram responses, olfactory-guided food finding, and sexual and social odor investigation after two-week exposure to inhaled chemicals, as transcription factor Skn-1a knockout mice (Skn-1a-/-) lacking TRPM5-MCs showed compromised physiological and behavioral phenotypes. Additionally, Skn-1a-/- mice failed to upregulate cell proliferation in the posterior region or undergo epithelial remodeling in the highly stimulated anterior dorsal region during chemical exposure, indicating impaired MOE plasticity. Here, we further investigated the role of TRPM5-MCs in olfactory system plasticity by using immunohistochemistry and olfactory behavior assays to determine the impact of chemical exposure on MOB morphology and function in control and Skn-1a-/- mice. Our preliminary results indicate that chemical-exposed control mice show a greater reduction in the size of NQO1+ dorsal glomeruli than Skn-1a-/- mice, but the latter exhibit a global decrease in the immunofluorescence signal for the activity-dependent dopaminergic cell marker tyrosine hydroxylase and higher odor investigation in a habituation-dishabituation odor discrimination assay. These results reveal TRPM5-MC-dependent, MOE region-specific adaptive plasticity during environmental chemical challenge and suggest that the influence of TRPM5-MCs on MOE maintenance may affect MOB morphology and odor discrimination.

The Role Of The Olfactory Bulb Sniff Rhythm In Sensory Cognition
Andrew Sheriff1,2, Vivian S Nguyen2, Leslie M Kay1,2
1University of Chicago, Department of Psychology, Chicago, IL, United States, 2Institute for Mind and Biology, Chicago, IL, United States

The olfactory nerve excites olfactory bulb (OB) neurons with each inhalation producing a sniff-locked slow rhythm that coordinates OB neural oscillations at higher frequencies. A growing body of literature shows interactions between the OB sniff rhythm and hippocampal (HPC) and cortical areas in humans underlying normal brain function and cognitive processes, including memory. In mice, both HPC theta and the OB sniff rhythm are present in both the OB and HPC during locomotion. These rhythms overlap in frequency, which suggests that they interact during behavior. To test the functionality of the OB sniff rhythm on neurophysiology and behavior, we performed olfactory bulbectomy (OBx) in young Long Evans rats just post-weaning to mimic congenital anosmia. This was followed many weeks later by implantation of probes to measure nasal respiration and electrodes to measure local field potentials in piriform cortex, HPC, and visual cortex. Recordings were conducted while rats foraged for 20 minutes in both dark and dimly lit environments with olfactory or visual spatial cues, respectively. Data from intact rats show similar patterns of high coherence at OB sniff frequency between distal brain systems (e.g., OB to visual cortex) while they forage in both conditions. OBx rats show significant differences in respiratory coupling and interestingly, altered coherence patterns between areas in visual versus olfactory foraging contexts. Further testing includes a nasal trigeminal discrimination task to compare learning between OBx and control animals during the same defined sensorimotor act that requires sniffing.

Bulbotomy Blunts But Does Not Eliminate Concentration-Dependent Preference For Sucrose And Maltrin In Long-Term Intake Tests In C57Bl/6J And T1R2+T1R3 Knockout Mice.
Ginger D. Blonde, Chizuko Inui-Yamamoto, Lauren Mariotti, Matias Campora, Alan C. Spector
Dept. of Psychology & Program in Neuroscience, Tallahassee, FL, United States

Previous work suggests that olfactory input plays a role in both short- and long-term drinking behaviors by rodents to sugars and maltodextrins. Here, the impact of bulbotomy on long-term intake and preference to sucrose and Maltrin (a maltodextrin) was investigated using C57BL/6J (B6) and T1R2+T1R3 sugar receptor knockout (KO) mice. Following functionally confirmed (buried food test) bulbotomy (BULB-B6, n=13; BULB-KO, n=7) or sham surgery (SHAM-B6, n=8; SHAM-KO, n=8), mice were given 46h 2-bottle tests pitting ascending concentrations (2-32% w/v) of sucrose and Maltrin against water. KO mice showed lower intake and preference than B6 mice for sucrose, but not for Maltrin. Bulbotomy further reduced sucrose preference by KO mice at dilute concentrations (2-8%; p’s<0.01) but BULB-B6 mice were only marginally lower than SHAM-B6 (p=0.06). These results confirm earlier studies suggesting that intact olfactory bulb projections are critical for sucrose consumption in the absence of normal “sweet” taste signaling, but are largely unnecessary when T1R-dependent signaling is intact. On the other hand, Maltrin preference and intake were significantly reduced in both BULB groups at low concentrations (p’s<0.05). Thus, bulbar projections appear necessary to promote Maltrin intake, at least at dilute concentrations, regardless of T1R2+T1R3. That both BULB groups preferred higher concentrations, here and in other studies, contrasts with severe bulbotomy-induced attenuation of licking in short-term tests and may be due to postingestive influences on long-term tests; but it is clear that bulbotomy does not eliminate motivation to consume palatable stimuli. Taken together, these results demonstrate the complex coordination of multiple systems to promote ingestion of preferred carbohydrate solutions.

Olfactory Bulbotomy Blunts Concentration-Dependent Responsiveness To Intralipid, Sucrose And Na-Saccharin, But Not To Quinine Hydrochloride And Citric Acid In A Brief Access Licking Test In Mice
Chizuko Inui-Yamamoto, Fabienne Schmid, Ginger D. Blonde, Tadashi Inui, Alan C. Spector
Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, United States

Recently, we reported that bulbotomized (BulbX) mice, which have their olfactory tract transected, display severely blunted concentration-dependent licking responses to sucrose and a maltodextrin regardless of the presence or absence of the T1R2+T1R3 “sweet” taste receptor. Here, in two separate experiments, we explored whether such bulbotomy-induced deficits occurred in mice when other normally preferred (Experiment 1: 0.625-20% Intralipid (IL) and 0.1-50 mM Na-saccharin (Sac); 1-32% sucrose as a positive control replication) and avoided (Experiment 2: 0.01–20 mM quinine hydrochloride (QHCl) and 0.3–100 mM citric acid) taste stimuli were tested along with water in a series of 30-min brief access (10-s trials) licking tests. In Experiment 1, concentration-dependent licking of IL and sucrose were severely blunted (p’s≤0.001) in food-deprived (~19h) C57BL/6J (B6) BulbX mice (n=14-17) relative to sham-operated counterparts (SHAM, n=12); BulbX mice also had moderate decreases in Sac licking (p=0.026). In contrast, in Experiment 2, licking of QHCl and citric acid did not differ between water-deprived (~19h) BulbX (n=12) and SHAM (n=12) B6 mice, nor between BulbX (n=13) and SHAM (n=12) T1R2+T1R3 receptor knockout mice, with all groups decreasing licking in a concentration-dependent manner (p’s≤0.001). All BulbX mice included in analyses failed the Buried Food Test (p’s≤0.001). The sucrose results replicate prior findings and the Sac results extend the effect to a non-caloric sweetener. The fact that IL, but not QHCl and citric acid, responsiveness was also severely impaired, suggests that an intact anatomical connection between the olfactory bulb and its central targets is necessary for normally preferred taste stimuli to maintain their efficacy at driving licking in short-term tests.

Potential For Cell-Based Therapy To Treat Hyposmia In A Mouse Model
Sarah Kurtenbach, Garrett M. Goss, Stefania Goncalves, Nirupa Chaudhari, Bradley J. Goldstein
University of Miami, Miami, FL, United States

Olfactory losses occur in conditions including post-viral olfactory disorder, aging (presbyosmia), or trauma. However, effective treatments are lacking. Evidence suggests that damage at the olfactory epithelium (OE), the peripheral organ for the sense of smell, may underlie many olfactory losses. Here, we sought to evaluate the potential for development of a cell-based therapy for OE repair in an animal model.  Because mice normally reconstitute the OE following experimental injury, evaluating the contribution of engraftment-derived neurons following cell-based therapy is a challenge. Therefore, we developed a mouse model of inducible hyposmia, useful as a host in which to test intranasal cell delivery. Tamoxifen-inducible hyposmic adult mice were generated by conditional deletion of the ciliopathy-related IFT88 gene in the olfactory sensory neuron lineage. Upon chemical-induced olfactory injury using methimazole, mice received tamoxifen and either a purified basal stem cell infusion or vehicle intranasally. Histologic assessment demonstrated engraftment and robust production of olfactory sensory neurons projecting into the olfactory bulb. Using the inducible hyposmia hosts, recovery due to engraftment-derived neurons was assessed by electrophysiology and behavioral assay. Additionally, we investigated mechanisms in culture that permit the expansion of engraftment-competent adult OE basal cells. Our findings suggest that delivery of olfactory progenitor cells intranasally may be of therapeutic potential, and provide a basis for further study of cellular therapies for anosmia.

Recovery From Anosmia Reduced Glomerular Dopamine Independent Of Foraging Success
KHALEEL I. QUASEM1, Brad R. Savard2, Thomas G. Mast1,2
1Eastern Michigan University, Ypsilanti, MI, United States, 2Eastern Michigan University, Ypsilanti, MI, United States, 3Eastern Michigan University, Ypsilanti, MI, United States

  Damage to the olfactory nerve reduces olfactory bulb (OB) dopamine (DA) production. Dopamine (DA) is proposed to participate in gain control and lateral inhibition during OB odor processing. This has been difficult to prove since damaging the olfactory nerve renders animals anosmic and incapable of olfactory behaviors. Previous studies suggest that intranasal lavage with dilute detergent solution reduces OB dopamine content without damaging the olfactory nerve, and thus sparing at least some olfactory behaviors. Our goal is to use recovery from peripheral lavage  to study odor behaviors with and without OB dopamine. Defining a time point with patent olfactory behavior and reduced DA levels is essential in understanding the role of DA in OB processing. As an initial step, OB DA synthesis following intranasal lavage needs to be quantified. In this study, we quantify tyrosine hydroxylase (TH) expressing fibers within the glomerular neuropil as well as cell bodies in the glomerular layer following 24-, 48-, and 120-hour recovery periods. Olfactory behavior was measured using the buried food test. Both TH expressing fibers and cell bodies were reduced 48 hours following intranasal lavage compared to sham-treated animals. Importantly, these same mice had normal olfactory ability as measured by latency and success rate in the buried food task. We conclude that 48-hours after intranasal lavage is an appropriate recovery period to study olfactory processing with reduced OB DA.  

Paving A Path Towards Single Olfactory Receptor Activation Using Synthetic Aptamers
Shani Agron1, Shireen Fseisy2, Itai Rusinek2, Gil Loewenthal2, Ido Bachelet2, Noam Sobel1
1Weizmann Institute of Science, Rehovot, , Israel, 2Augmanity ltd., Rehovot, , Israel

Our nose allows us to detect and discriminate between a vast range of structurally diverse odorants thanks to millions of olfactory receptors (ORs) of about 400 different types.  Each OR may react to a repertoire of different odorants and each odorant can activate more than one type of OR, this constitutes a highly complexed combinatorial code that results in odor perception. The contribution of a given olfactory receptor to olfactory perception remains unknown. A potentially helpful key to this riddle would be a synthetic agonist for a single OR type. Aptamers are short single stranded oligonucleotide sequences (DNA, RNA, or synthetic analogs of the two) that can fold into stable 3D structures and bind to different targets with high affinity and specificity. Exploiting these advantages, we selected aptamers to olfactory receptor 1A1 (OR1A1) using systematic evolution of ligands by exponential enrichment (SELEX) technique on cells that express the receptor. To gain specificity we introduced a negative selection step at an early stage of the SELEX using the same type of cells with no OR1A1 expression. Using a novel approach, we have selected aptamers that specifically bind to OR1A1. This is the result of two independent selection procedures, one was done in the presence of dihydrojasmone, a known odorant for OR1A1 and the second with no odor presence. A repertoire of aptamers towards the odor bound and unbound forms of the receptor may shed some light on the areas involved in odor binding by ORs. Additionally, we are currently testing rather these aptamers can modulate the receptor activity and to induce or alter odor perception.   

Aversive Learning Increases Neurotransmitter Release From Primary Olfactory Sensory Neurons

Predicting danger from previously associated sensory stimuli is essential for the survival of animals in a dynamic environment. The potential contribution from altered sensory inputs has been reported, but the underlying mechanism remains elusive. The mammalian olfactory system is an excellent model for investigating such mechanisms, as primary olfactory sensory neurons (OSNs) project their axons directly to the olfactory bulb (OB) and their synaptic releases are subject to cortical influence and neuromodulation. Here we found that pairing optical stimulation of a single M72-ChR2 (channelrhodopsin-2)-YFP glomerulus with foot shock during the conditioning session led the mice to freeze to the optical stimulation alone during the retrieval session 24 hrs later. Release properties of M72 OSNs were assessed by light-evoked postsynaptic events in genetically-labeled, glutamatergic external tufted cells innervating the M72 glomeruli in the OB slices. We observed a significantly higher release probability of OSNs projecting to the M72 glomeruli that were fear conditioned (pair pulse ratio in percentage: 30.26±3.82, n=16) than the control ones (unstimulated: 59.16±3.67, n=28 or stimulated but unpaired with foot shock: 55.22±4.89, n=7; one-way ANOVA, p<0.01), as well as a significant increase in the spontaneous excitatory postsynaptic events, suggesting a change in presynaptic release. Further immunohistochemical and pharmacological studies suggest a role of decreased GABAB receptor level of the fear conditioned M72 glomeruli in this process. Notably, a positive correlation between the release probability and freezing behavior was evident. These results suggest that aversive learning enhances peripheral olfactory inputs, which may contribute to the behavioral outcome.

Coding Spatiotemporal Characteristics Of Odor Signals
Yuriy Bobkov1, Il Park2, Brenden Michaelis3, Thomas Matthews4, Matthew Reidenbach3, Jose Principe5, Barry Ache1,6
1Whitney Laboratory for Marine Bioscience, Center for Smell and Taste, University of Florida, Gainesville, FL, United States, 2Department of Neurobiology and Behavior, SUNY Stony Brook, Stony Brook, NY, United States, 3Department of Environmental Sciences, University of Virginia, Charlottesville, VA, United States, 4Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, Maraphon, FL, United States, 5Department of Electrical and Computer Engineering, University of Florida,, Gainesville, FL, United States, 6Department of Biology and Neuroscience, University of Florida, Gainesville, FL, United States

Published evidence has identified a subpopulation of ORNs in lobsters that consists of intrinsically rhythmically active, ‘bursting’ ORNs (bORNS) with unique functional properties: they encode olfactory information by having their rhythmicity entrained by the odor stimulus; they accurately encode the interval since the last odor encounter up to 10s of sec; they do this instantaneously, independent of memory; and that bORN-derived input provides a heretofore unsuspected way of navigating turbulent odor plumes.  We are currently extending this understanding by electrophysiological recording and calcium imaging from bORNs and interneurons in the first olfactory relay of the lobster.  To date we have characterized the molecular receptive range (MRR) of bORNs.  We show that the MRR of bORNs significantly overlaps that of canonical tonic ORNs (tORNs), arguing that bORNs and tORNs may target the same glomeruli in a receptor-specific manner.   We are in the process of functionally mapping the central projection of bORNs in an attempt to show that bORN-derived input is possibly selectively processed in a dedicated, midbrain neuropil, the accessory lobe (AL).  The AL is known from our previous work to receive olfactory input indirectly via olfactory lobe (OL) glomeruli, and project to the forebrain independently of and in parallel with the OL.  Based on our new functional evidence and previous understanding of the AL, we identify a potential strategy for synaptic processing of bORN-derived information at the first olfactory relay.  Our findings further support the hypothesis that encoding odor time is a fundamental feature of olfaction that can be used to navigate turbulent odor plumes.

Olfactory Sensory Neuron Maturation In The Young Adult
Teresa Liberia1, Diego J. Rodriguez-Gil2, Charles A. Greer1
1Yale University, New Haven, CT, United States, 2East Tennessee State University, Johnson City, TN, United States

The ongoing neurogenesis of olfactory sensory neurons (OSN) and integration of their connections to olfactory bulb (OB) circuits suggest that the mechanisms underlying map formation must be maintained throughout life. However, the mechanisms responsible for establishing and maintaining these orderly maps in the adult olfactory system are unknown. To investigate if adult OSN neurogenesis differs from what is known about the development of these cells at perinatal ages, we labeled terminally dividing basal cells in the olfactory epithelium (OE) of 25-day-old (P25) mice with BrdU pulse-labeling. Combining this strategy with in-vivo fate mapping allowed us to track both OSN maturation and axon extension. Our results show that there are regional differences in the neurogenesis rate of the septal OE and radial migration of P25-born OSNs. Regarding molecular maturation, OSNs transition from immature to mature OSNs in 8-10 days following basal cell division, indicating that this process takes slightly longer in mature animals compared with perinatal stages. Concordant with these findings of OSN maturation, axonal extension in P25 animals also occurs gradually, beginning 2 days after basal cell division and continuing for 6-8 more days until they innervate the glomerular neuropil 8-10 days after basal cell division. Collectively, these analyses provide insights into adult neurogenesis in the olfactory system by showing how the molecular maturation relates to neural migration in the septal OE and the innervation of the OB by P25-born OSNs. In conclusion, we demonstrate that OSN neurogenesis in the mature olfactory system show regional differences compared to perinatal stages, but that newborn OSN molecular maturation and axon extension grossly recapitulates the mechanisms observed in the perinatal stages.

Decoding The Ant Sniffer: Functional Characterization Of Odorant Receptors In Harpegnathos Saltator
Jenna Longo, Kendall Ham, Bri Pomonis, Gregory Pask
Bucknell University, Lewisburg, PA, United States

Olfaction is a critical modality for how insects interpret their environment and other individuals around them. Specifically in eusocial species, these olfactory cues determine how the nestmates can interact to form a hierarchy of workers and establish a reproductive division of labor. While there are several species, such as bees and wasps, that are eusocial, our research focuses on Harpegnathos saltator, the Indian jumping ant, which is considered primitively eusocial. These ants exhibit adaptable behaviors that allow workers to transition to egg-laying reproductives should the queen no longer be present. Chemical detection of H. saltator reproductives is critical for maintaining the colony hierarchy, making this species a unique model for eusocial communication. H. saltator have a finely-tuned olfactory system consisting of nearly 350 unique odorant receptors (ORs), one of the more expansive OR families described in insects. Previous research has explored the 9-exon subfamily of H. saltator odorant receptors (HsOrs) and found that this expansive subfamily functions as narrowly-tuned cuticular hydrocarbon (CHC) detectors. Using heterologous expression of HsOrs in transgenic Drosophila, we are continuing to examine CHC tuning across the rest of the odorant receptor repertoire. By prioritizing HsOrs that show enriched expression in worker antennae versus males, this work will contribute to a more representative analysis of HsOr function and offers the most ORs characterized to date in any insect. This large HsOr deorphanization data set can provide insight into the functional diversification of chemical receptors that allow for eusocial communication.  

Importance Of Olfaction In Children And Adolescents &Ndash; Development And Implementation Of A Questionnaire
Annika Dworschak, Luca Parisato, Valentin A. Schriever
Abteilung Neuropädiatrie , Dresden, *, Germany

Aim: Little is known about the importance of olfactory information in childhood and adolescence. Aim of this study was to develop a questionnaire to measure the importance of olfaction in this age group. Material and methods: The study was conducted in two parts: 1) development of the questionnaire, 2) implementation of the questionnaire. Part 1) 191 volunteers took part (age: 14.4±1.7 years). The pilot-questionnaire consisted of 33 four-scaled items formulated as personal statements regarding three subscales i) food, ii) social and iii) environment. Participants indicated how much they agree with the statements. The best fitting items were chosen for the final version of the questionnaire. Part 2) The questionnaire was administered to investigate the influence of age, sex and olfactory function on the significance of olfaction to 208 participants (50% girls; age 11.4±3.4 years). Olfactory threshold and odor identification ability were assessed using the “Sniffin’ Sticks”. Results: Part I) The final version of the questionnaire consists of 15 items with good internal reliability (Cronbach’s Alpha=0.79). The three subscales are positively correlated (r=0.27–0.32, p<0.001) but can be discriminated from each other. Part II) A positive correlation between age and the questionnaire score was observed (r=0.46, p<0.001). Girls scored significantly higher on the subscale food (F=4.20, p=0.042) and the complete questionnaire (F=3.87, p=0.05). Moreover a positive correlation between odor identification score and the subscale environment could be found (r=0.206, p=0.038). Conclusion: The new questionnaire is a valid tool to measure the individual significance of olfaction in children and adolescents, which is influenced by age, sex and olfactory function.

Plc Variants Define A Potential, Global Sensory Modulation System In The Vomeronasal Organ
Norah Koblesky1,3, Leon Fodoulian2, Ivan Rodriguez2, Lisa Stowers3
1University of California-San Diego, La Jolla, CA, United States, 2University of Geneva, Geneva, *, Switzerland, 3The Scripps Research Institute - La Jolla, La Jolla, CA, United States

How individuals experience the same stimuli differently is a mystery, and only by learning about such differences can we understand sensory coding. Peripheral sensory neurons, viewed as passive information collectors, are overlooked as potential sites of sensory modulation. However, it was recently found that peripheral pheromone neurons of mice(VSNs) are directly modulated by progesterone, which alters perception and behavior; further, modulation occurs through phosphorylation of PLCβ2, VSN’s presumed primary signaling element. Modulation of VSN activity is more efficient than manipulation downstream, yet to what extent direct modulation occurs in the vomeronasal organ(VNO) is unknown. PhospholipaseC(PLC) signaling is essential for VSN activity and progesterone modulation, making PLC phosphorylation an appealing modulation target. Indeed, each of the 18 PLCs has a unique phosphorylation capacity and functional response to phosphorylation, and it was recently shown that PLCβ2 is not the only functional PLC in VNO. Yet, the expression, pattern, and function of PLCs in VNO is unknown. For direct sensory modulation to be global, PLC expression must be diverse, distinct, and logical - using scRNAseq and histology, we characterize PLC expression in VNO across these three parameters. VSNs express 9+ PLC variants; moreover, each VSN only expresses one PLC variant, implying that different VSNs signal through different PLCs. Certain PLCs segregate with certain sensory receptors, such that (e.g) PLCβ2 only signals in cells responding to certain stimuli. It is known that PLCs are functionally distinct, indicating that our results have vast implications for VNO function. We hypothesize that diverse, distinct PLC expression could allow for modulation of VSN activity in a context-specific manner.

Expression Analysis Of A Novel Putative Pheromone Receptor Ancv1R In Mice.
Hiro Kondo1, Hikoyu Suzuki2, Hidefumi Nishida1, Ryota Yoda1, Tetsuo Iwata1, Takayuki Enomoto1, Junji Hirota1, Masato Nikaido1
1Tokyo Institute of Technology, Yokohama, *, Japan, 2Nihon BioData Corporation, Kawasaki, *, Japan

Pheromones are crucial for eliciting social and sexual behaviors in diverse animal species. The vomeronasal receptor type-1 (V1R) genes, encoding members of a pheromone receptor family, are highly variable in number and repertoire among mammals due to extensive gene gain and loss. Recently, we identified a novel putative pheromone receptor gene belonging to the V1R family, named ancient V1R (ancV1R), which is shared among most bony vertebrates from the basal lineage of ray-finned fishes to mammals. Genome analyses revealed that pseudogenization of ancV1R in some tetrapods correlates strongly with VNO degeneration, suggesting important function of ancV1R in pheromone detection. Here, we report unique molecular characteristics of mouse ancV1R gene. Expression analysis revealed that ancV1R is expressed in the almost entire vomeronasal sensory neuron (VSN) layer labeled by the olfactory maker protein probe, whereas canonical V1Rs and V2Rs are sparsely expressed in the apical and basal layers of VSNs, respectively. To further characterize ancV1R-expressing cells, we performed two-color ISH, and revealed that ancV1R is expressed in both types of VNSs, apical V1R and Gnai2 expressing-VSNs and basal V2R and Gnao-expressing VSNs. Thus, ancV1R is distinct from canonical V1Rs in terms of evolutionary conservation and the expression pattern. Further functional analyses will provide new insights into the molecular mechanisms of pheromone detection.

The Signaling Power Of Olfaction: Effect Of Hexanal On Trust
Daan van Nieuwenburg1, Jasper H.B. de Groot1,2, Monique A.M. Smeets1,3
1Utrecht University, Social Health Organizational Psychology, Utrecht, *, Netherlands, 2University of Pennsylvania, Department of Neurology, Philadelphia, PA, United States, 3Unilever R&D, Vlaardingen, *, Netherlands

Body odors and natural aromas are complex odorant mixtures with overlapping chemical composition. These shared chemical structures may be biomarkers of social signaling that help flowers attract insects for pollination and help animals and humans find mates. A putative biomarker is hexanal (green grass odor). We tested whether hexanal has social communicative powers in humans 1) as a singular compound and 2) when embedded in a (simple) mixture. Since the sense of smell is holistic and humans have difficulties identifying single compounds in odor mixtures, hexanal may exert signaling power even when not detected in a mixture. Methods: In Experiment 1, 90 females in a between-subject design endowed money to a trustee in a Trust Game smelling either unmasked hexanal (0.01 % v/v), eugenol odor (10% v/v) or masked hexanal (a mix of the former). In Experiment 2, 35 females were tested in a within-subjects design with similar odor conditions using a facial trust morph paradigm. Participants rated the trustworthiness of the facial morphs. Odors were rated for pleasantness, intensity and discrimination. Results: Planned contrast analysis showed that in Experiment 1 participants endowed more money to a trustee when smelling masked hexanal compared to eugenol and unmasked hexanal, F(2, 62.73) = 5.44, p <.01. In Experiment 2, participants rated ambiguous faces as more trustworthy when exposed to unmasked and masked hexanal, compared to eugenol F(2, 31) = 3.50, p = .042. No differences were found in explicit ratings of pleasantness and discrimination of masked vs. unmasked hexanal. However, there were differences in perceived intensity. Conclusion: These results demonstrate effects of hexanal supporting its purported role in social signaling by enhancing interpersonal trust.

Olfactory Experience With Semiochemicals Influences Sex-Specific Olfactory Receptor Expression
Aashutosh Vihani, Hiroaki Matsunami
Duke University, Durham, NC, United States

We observe a robust difference in the number of olfactory sensory neurons (OSNs) that express specific olfactory receptors (ORs) in sex-separated male and female mice. Surprisingly, this sex difference is plastic as co-habitation with the opposite sex is sufficient to attenuate the dimorphism, raising the possibility that odor experience by the opposite sex drives this plasticity. To test this we asked if sexually dimorphic ORs respond to known sex-specific odorants. Using phosphorylated S6 ribosomal subunit capture, we identify male-specific semiochemicals as potent ligands for ORs exhibiting sexually dimorphic expression. Our data is consistent with the idea that odor experience by monomolecular ligand is sufficient to attenuate the sexually dimorphic expression of specific ORs. Finally, we show the generation of sexually dimorphic OR expression is at least partly Bax-dependent, suggesting a link with odor exposure and cell death. Altogether, our results support the model that prolonged odor exposure to sex-specific odorants causes sexually dimorphic expression of ORs by modulation of sensory neuron lifespan.

Orthonasal And Retronasla Olfactory Function In Patients With Olfactory Loss: Relation To Quality Of Life
Yunpeng Zang, Anna Oleszkiewicz, Antje Haehner, Dahae Park, Thomas Hummel
TU Dresden, Dresden, *, Germany

In this study we examined the predictive value of ortho- and retronasal indices of olfactory function on a wide spectrum of health and sociopsychological factors, including olfaction-related quality of life, life satisfaction, overall health and depression. Participants were 178 ENT patients (Mean age=58±1 years) representing various causes of olfactory loss: idiopathic (n=51; M=63±2), sinunasal (n=27; M=56±3), head trauma (n=33; M=51±2), infections of the upper respiratory tract (n=67; Mage=59±2). They completed self-report questionnaires and underwent olfactory testing using Sniffin’ Sticks (orthonasal testing) and “taste powders” (intraorally applied odors, retronasal testing). Then we have included retronasal olfaction score, and there was an improvement of model’s predictive value when retronasal score was added. This study suggests that retronasal function significantly improves predictions of health and sociopsychological functioning of patients with olfactory loss. Results bordered at the conventional significance level may be attributed to the characteristics of the study sample comprising patients.  

Wednesday, April 17, 2019

7:30 - 9:00 AMEstero Foyer

8:00 - 10:00 AMEstero Ballroom
Poster Session V

Chemosensory Receptors Of Cydia Pomonella (Lepidoptera: Tortricidae)
Alberto Maria Cattaneo1, Yuriy V. Bobkov2, Francisco Gonzalez3, Stephen F. Garczynski4, Peter Witzgall1, William B. Walker III1
1Swedish University of Agricultural Sciences, Department of Plant Protection Biology, Chemical Ecology Horticulture Research Unit, Alnarp, *, Sweden, 2University of Florida, Whitney Laboratory, Center for Smell and Taste, and McKnight Brain Institute, Gainesville, FL, United States, 3ChemTica Internacional S.A., Sto. Domingo, Heredia, *, Costa Rica, 4USDA-ARS, Temperate Tree Fruit and Vegetable Research Unit, Wapato, WA, United States

Cydia pomonella (Lepidoptera: Tortricidae) is a major pest of apple, pear and walnuts. For its control, alternative strategies targeting the olfactory system, such as mating disruption, have been combined with insecticide applications. The efficacy of these strategies guided the direction of efforts for the functional characterization of codling moth chemosensory receptors to implement further control methods based on targeting chemical sensing. With the advent of transcriptomic analysis, chemosensory receptors transcripts have been identified in antennal transcriptomes of C. pomonella. Heterologous expression of full-length chemosensory receptor open reading frames in empty neurons of Drosophila melanogaster and in Human Embryonic Kidney cells allowed detailed functional studies of receptors including ligand specificity (deorphanization) and receptors' activity patterns. Among different classes of antennal receptors, several odorant receptors of C. pomonella (CpomORs) have been characterized as specific for kairomones (CpomOR3), pheromones (CpomOR6a) and compounds emitted by non-host plants (CpomOR19). Physiological and pharmacological studies of these receptors confirmed their ionotropic properties, by forming functional channels with the co-receptor subunit of CpomOrco. Interestingly, molecular biological analysis suggests that at least some receptors of C. pomonella are expressed as a complex combination of splice-isoforms and their expression pattern may correlate with the expression of other ion channels (e.g. CpomOR53 and TRPA5). Investigation of chemosensory capabilities in the codling moth has practical outcomes for the development of control strategies and has inspired novel trends to control this pest by integrating alternative methods to interfere with insect chemosensory communication.

Fear, Fright, Flight: Can Human Body Odors Convey Emotion Intensity?
Jasper H.B. de Groot1,2, Peter A. Kirk1, Jay A. Gottfried1,3
1Department of Neurology, University of Pennsylvania, Philadelphia, PA, United States, 2Department of Social, Health, & Organizational Psychology, Utrecht, *, Netherlands, 3Department of Psychology, University of Pennsylvania, Philadelphia, PA, United States

Humans can implicitly inherit emotional states (e.g., fear) based on another person’s body odor (BO). Whereas prior research has treated emotions as categorical constructs, here we focus on another important aspect of emotions – the degree of emotional intensity – and whether this information can be communicated chemically. Here we tested the hypothesis that there is a dose-response relation between experienced fear intensity by a sender (low, medium, high) and experienced fear intensity by a receiver (a lower criterion to identify fear across a spectrum of faces between fear, disgust). Method: Study 1 entailed collecting BOs from 36 male senders induced under either fearful (horror clips) or calm (control) conditions. Using Partial Least Squared-Discriminant Analysis, senders were then successfully subdivided into 3 fear intensity groups (low, medium, high) based on their regression-weighted subjective ratings and physiological responses. The goal of the subsequent receiver Study was to dissect components of fear odor processing at the behavioral, physiological, and neural levels, by combining fMRI, olfactory psychophysics, and pattern-based imaging analysis. In a double-blind within-subjects design, 31 female receivers were exposed to the 3 levels of fear BO and control BO on separate trials during fMRI scanning, while rating faces morphed between fear and disgust. Results: All BOs (fear, neutral) were indistinguishable, iso-intense, and iso-pleasant; yet, all fear odors (low, medium, high) significantly reduced receivers’ subjective criterion to identify fear in ambiguous faces, F(1, 26) = 13.44, = .001; and FOs induced longer sniffs (= .039) (vigilance). The neural data (to be analyzed) will give further insights into the functional organization of social odor coding in the human brain.

Associative Olfactory Fear Learning Alters Spatiotemporal Coding Of Olfactory Bulb Output Cells
Jordan M. Ross, Max L. Fletcher
University of Tennessee Health Science Center, Memphis, TN, United States

Associative fear learning produces fear toward the conditioned stimulus (CS) and often generalization, the expansion of fear from the CS to similar, unlearned stimuli. However, how fear learning affects early sensory processing of learned and unlearned stimuli in relation to fear of these stimuli remains unclear. Using awake wide-field calcium imaging of excitatory post-synaptic olfactory bulb (OB) cells, we established that the glomerular representations of neutral odorants become more similar to the representation of the CS following fear learning, possibly providing an initial neural basis for fear generalization. Additionally, we identified two distinct circuits mediating odor-shock glomerular enhancements; one associative learning-independent but CS-specific, and another that requires associative learning and supports global enhancements. As our glomerular imaging encompassed responses from heterogenous cell types, we are now focused on investigating the learning-induced alterations of specific OB cell populations. Using a similar fear learning paradigm in combination with awake 2-photon imaging, we demonstrate that responses of mitral cells, superficial tufted cells, and juxtaglomerular cells are differentially modulated following fear learning, which may support the previously identified distinct mechanisms of glomerular enhancements. Many of the changes are temporally dynamic, even persisting after odor offset, which reflects rich sculpting of somatic responses. Furthermore, fear learning potentiates mitral cell responses of non-CS odors, regardless of peak timing or initial polarity. This acts to increase the correlation between CS and non-CS responses, especially throughout the duration of the odor presentation which may be relevant to the behavioral time scales of generalized freezing.

Conformational Sensing By The Mouse Olfactory Receptor Olfr2
Kevin Ryan, Min Ting Liu
Department of Chemistry and Biochemistry, The City College of New York , New York, NY, United States

There is currently no structural biology information describing what takes place inside a mammalian olfactory receptor (OR) when it binds to, and is activated by, an odorant. Especially mysterious is how an odorant’s carbon chain can define the receptive range of an OR. As a model system to investigate carbon chain recognition by ORs, we are studying the rodent Olfr2 receptor (a.k.a. OR-I7), which is specific for the aldehyde group and prefers 8-carbon aliphatic chains. Proteins that bind specifically to small molecules with rotatable bonds typically bind their ligands in one or very few ligand conformations. Carbon chains like that found in octanal can adopt many conformational isomers, or conformers, of similar energy, raising the question: Are specific conformers responsible for OR activation? To investigate this question, we used the medicinal chemistry strategy of conformational restriction. We made and tested in dissociated olfactory receptor neurons from the UbI7 mouse two octanal analogs, cis- and trans-2-(4-ethylcyclohexyl)ethanal. These ligands spatially restrict, in relation to the aldehyde group, in different ways, the last two carbons in the octanal chain. The order of potency of the three ligands was found to be: trans > octanal > cis, and the cis isomer appears to be a partial agonist. Our results support the idea that Olfr2 senses the conformations of the octanal carbon chain. From the data presented we deduce the optimal octanal conformation for Olfr2 activation.

Awake, In-Vivo Imaging Of Experience-Induced Changes Of Taste Representation In Mouse Gustatory Cortex.
Stephanie M Staszko, John D Boughter, Max L Fletcher
University of Tennessee Health Science Center, Memphis, TN, United States

A major drawback of prior taste learning studies has been the inability to reliably follow individual cell taste responses across days, thus it still unclear how individual cell taste representations change with experience. Current research in our laboratory utilizes miniature head-mounted microscopes (miniscopes) to investigate taste coding in the gustatory cortex (GC) of awake, behaving mice. A primary benefit of this technique is the ability to image the same population of neurons across multiple days in deep brain regions such as GC. Thus, our present research aims to understand how experience alters activity in single cells in mouse GC using both non-associative (passive experience) and associative learning (CTA) paradigms. Current imaging experiments are focused on “central” GC (AP+1.5mm, ML+3.3mm, DV-2.1mm). Mice are water deprived and trained to lick taste stimuli from a Davis Rig. Once trained to lick from sipper tubes, animals are exposed to a taste panel including sweet, sour, salty, bitter, and umami stimuli. Animals receive two random presentations of each stimulus (separated by a diH2O rinse) each day over the course of five days. Immediately following the non-associative learning paradigm, animals enter a CTA paradigm in which they consume lithium chloride from a sipper tube and are tested the following day with presentations of sodium chloride and diH2O, with low sodium chloride consumption reflecting learning. To date, data show spatially overlapping populations of taste-responsive and non-taste responsive cells exist within GC, with a clear decrease in activity of non-taste responsive cells over days. Current experiments and analyses are focused on understanding changes in single cell activity following CTA.

Feeding Control Via Multimodal Taste Integration In Pharyngeal Neurons In Adult Drosophila
Yu-Chieh D. Chen1, Ryan M. Joseph2, Anupama A. Dahanukar1,2
1Interdepartmental Neuroscience Program, UC Riverside, Riverside, CA, United States, 2Department of Molecular, Cell and Systems Biology, UC Riverside , Riverside, CA, United States

In adult Drosophila, tastants are detected via taste sensilla in multiple organs throughout the body, present externally in the labellum, legs, wings and internally in the pharynx. Taste input originating from multiple classes of gustatory receptor neurons (GRNs) in different taste organs is thought to be processed in higher-order brain circuits for mediating behavioral output, yet how pharyngeal GRNs that are positioned at a crucial site for food evaluation contribute to feeding behavior remains unclear. We used a Pox-neuro (Poxn) mutant as a minimal taste system model in which all the external taste sensilla are transformed into mechanosensory sensilla, while all pharyngeal GRNs remain intact. In Poxn mutants, we genetically silenced all pharyngeal GRNs and found that feeding attraction to appetitive tastants and avoidance of aversive tastants were both abolished in binary choice assays, suggesting a key role for pharyngeal taste in food selection. Guided by our recent pharyngeal chemoreceptor reporter map, we used genetic intersectional strategies to selectively protect molecularly defined class of pharyngeal GRNs in otherwise taste-blind flies, allowing us test principles of taste coding and behavior in animals that possess only one type of taste neuron. Using single-fly quantitative FLIC assays to measure various micro-feeding parameters, we found that flies with distinct single classes of pharyngeal GRNs exhibited distinct, and in some cases opposing, micro-feeding behaviors in response to the same tastants. Further, Ca2+ imaging of selected pharyngeal GRNs revealed overlap in tastant sensitivity, as well as multimodal tastant-sensing properties. Together, our results suggest that distinct populations of pharyngeal GRNs can control micro-feeding parameters in synergistic or antagonistic ways.

Neurexin Isoforms May Coordinate Innervation Of Mouse Taste Bud Cells
Gennady Dvoryanchikov1, Damian Hernandez1, Nirupa Chaudhari1,2,3
1Department of Physiology & Biophysics, University of Miami Miller School of Medicine, MIAMI, FL, United States, 2Program in Neurosciences, University of Miami Miller School of Medicine, MIAMI, FL, United States, 3Department of Otolaryngology, University of Miami Miller School of Medicine, MIAMI, FL, United States

Taste buds are innervated by fibers of primary gustatory neurons. We asked if taste bud cells express synaptic recognition molecules that could promote interactions with afferent fibers. Neurexins (Nrxn1, 2, 3) are presynaptic proteins with numerous isoforms, permitting selective recognition between pre- and post-synaptic membranes in the CNS. Using RT-qPCR, we found that Nrxn1 is expressed only as the longer α-isoform, while Nrxn3 is expressed only as the truncated β-isoform. Nrxnα can exist as many splice variants, to confer synaptic specificity. Hence, we used primers flanking all 6 splice sites (SS1-SS6) for single-cell RT-qPCR. Taste bud cells were identified by GFP fluorescence (from PLCb2-GFP or Gad1-GFP mice for cell types 2 and 3 respectively). At SS1, SS3 and SS5 sites, both alternative forms of Nrxn1 could be detected in both type 2 and 3 cells. However, at the SS2 site, type 2 and type 3 cells express different splice variants. Another difference between the taste bud cell types was that we detected Nrxn3 only in type 2 cells and only as Nrxn3β. The difference between type 2 and type 3 cells was also reflected in markedly different patterns of staining with anti-Nrxn antibody. We also looked for Neuroligins (Nlgn1, 2, 3), known postsynaptic partners for Nrxns. Geniculate ganglion gustatory neurons express RNA for all three Nlgns; and immunohistochemistry revealed a punctate pattern of staining over taste buds, which was lacking over adjacent non-taste epithelium. Finally, we found that Neurexophilin, which can regulate the Nrxn-Nlgn interaction, is only expressed in type 2 cells. Thus, neurexins, with differentially expressed splice variants, may be good candidates for coordinating selective innervation of taste bud cells.

Feline Taste Cell Lines: A Promising Tool For Palatability Investigation In Cats
Christiane Gras1, Emilie A. Leclerc2, Isabelle Guiller2, Michael Krohn1, Aurelie de Ratuld2
1BRAIN AG, Zwingenberg, *, Germany, 2Diana Petfood, Elven, *, France

Cat food palatability performance strongly depends on the interaction between food properties, pet sensory equipment and individual preferences. Among the key drivers of palatability in cats, taste is of particular importance. Palatability enhancers are commonly added to cat formula to increase food acceptability, and sensory evaluations are conducted with cats to validate palatants performance. This crucial development step is time consuming and requires a high number of animals. The aim of this study was to develop a high throughput screening (HTS) cellular tool, based on genuine cat taste cells, able to mimic cats’ answer to taste compounds. Biopsy samples from cat lingual epithelium containing taste buds from circumvallate papillae were used to obtain primary taste cells. Isolated cell populations were immortalized. Different taste solutions including amino acids and complex palatants were tested with cats using sensory evaluation in order to select molecules that positively or negatively impacted palatability. The active tastants were used as benchmark to validate the taste functionality of the cell lines, using HTS-compatible cell-based functional assays, e.g. calcium and membrane potential imaging. Several proliferating cat taste cell populations that functionally responded to the same tastants than the cats were successfully generated. More importantly, synergistic effects observed in cat sensorial evaluation were also observed in cat taste cell assays. This unique in vitro cellular tool could be used to efficiently identify novel palatable ingredients for cat while reducing the number of sensory evaluations with animals. Moreover, it will allow a better understanding of the mechanisms behind cat taste perception and modulation.

The Innervation Of Taste Buds Differs Between Humans, Tree Shrews, And Mice
Brigit High, Courtney E. Wilson, Ruibiao Yang, Mei Li, Thomas E. Finger
Rocky Mountain Taste and Smell Center: University of Colorado School of Medicine, Aurora, CO, United States

Gustatory nerve fibers innervate mammalian taste buds and express P2X receptors, reflecting the obligate purinergic nature of gustatory transmission. These fibers arise from the facial nerve to innervate the fungiform papillae and from the glossopharyngeal nerve to innervate the circumvallate and foliate papillae. Acetylated tubulin serves as a marker for all nerve fibers, while P2X3 labels gustatory fibers as well as subset of mucosal nerve fibers. We utilized immunohistochemistry with these two markers as well as electron microscopy to compare the patterns of innervation of fungiform and circumvallate papillae of mice, humans and tree shrews (Tupaia belangeri), a member of the Euarchontoglires superorder of mammals whose phylogenetic classification has produced controversy due to it sharing features of both primates and rodents. Although the general pattern of innervation is conserved across all three species, we find increased density of innervation by P2X3-immunoreactive nerve fibers in humans compared to mice and tree shrews. In addition, the nerve fibers in human taste buds appear thicker and more tortuous as compared to mice. Further ultrastructural analysis is necessary to determine whether the details of connectivity in humans differ from those in mice and tree shrews.

Exploring Food Texture Sensation In Drosophila
John Mack, Tingwei Mi, Yali Zhang
Monell Chemical Senses Center, Philadelphia, PA, United States

The physical features of food, such as hardness or viscosity, significantly influence food preference in many organisms ranging from humans to fruit flies. Food mechanosensory neurons located at the taste organ detect the physical properties of food, enabling animals to evaluate food stiffness and viscosity. Our previous work using the fruit fly, Drosophila melanogaster as an animal model, has identified a protein named transmembrane channel-like (TMC), which in mammals is critical for hearing, as a vital mechanotransduction component underlying food texture sensation. To further elucidate the food mechanotransduction pathway, we performed an RNAi-based behavioral screen to search for the channel subunits and signaling components governing food texture sensation. Our genetic analyses show that the fly homolog of the mammalian tetraspan membrane protein of hair cell stereocilia (TMHS), is required for food texture sensation. Loss of tmhs leads to severe defects in the discrimination between soft foods containing 1% agarose and hard foods containing 3% agarose. Moreover, tmhs is expressed at the mechanosensory neurons in the fly tongue. In summary, our results implicate the fly tmhs as an essential gene regulating food texture sensation. In mammals including humans, both TMC and TMHS are required for hearing. Of great interest, our work shows that TMC and TMHS are also responsible for food texture sensation in flies. Therefore, we propose that food texture sensation in the fly and hearing in mammals may use a similar mechanotransduction pathway.

Sweet Taste Detection And Preference In Children Vs. Adults
Sara Petty1, Clara Salame1, Julie A. Mennella2, M. Yanina Pepino1
1University of Illinois Urbana-Champaign, Champaign, IL, United States, 2Monell Chemical Senses Center, Philadelphia, PA, United States

Adults and children might live in different sensory worlds. In particular, children prefer sweeter substances than adults do. This may be related to their increased energy need in periods of maximal growth and development. However, there is limited published data that uses the same methods to compare the taste worlds of children and adults, particularly with respect to taste sensitivity. Here we compared data collected from children aged 7-18yrs. (n=182) to data collected from several studies in adults aged 21-67yrs. (n=117) using identical, validated, methods.  We assessed sucrose detection thresholds by using a two-alternative, forced-choice paired comparison tracking procedure, and sucrose preference with the Monell 2-series, forced-choice tracking method. We found that sucrose detection thresholds were higher in children than adults (log means of -2.04±0.03 vs. -2.18±0.04 in children vs. adult respectively; ~9.2mM vs. 6.7mM sucrose; p<.01). As expected, children preferred higher sucrose concentrations than adults (595 ±22 mM vs. 433 ±27 mM; p<.0001). Sucrose detection threshold were not correlated to sucrose preference in either group (children, r=0.013; adults, r=0.166 both P’s>0.05). Our results indicate that children are less sensitive to detect sucrose than adults are, and confirms previous findings that children prefer higher concentrations of sucrose. However, sucrose detection thresholds did not predict preference, and therefore children's preference for heightened sucrose concentrations cannot be explained by a reduced sucrose sensitivity at detection levels. Further understanding of children’s taste perception world can help to contribute to the understanding of the motivations behind food choices made by children and their potential nutritional implications.

Spatio-Temporal Patterns Of Activity In The Gustatory Cortex Of Mice Engaged In A Cue-Taste Paradigm
Ke Chen, Joshua F. Kogan, Alfredo Fontanini
State University of New York at Stony Brook, Stony Brook, NY, United States

Despite decades of research, the basic logic underlying taste coding in the gustatory cortex (GC) remains intensively debated. The development of 2-photon calcium imaging has greatly expanded our perspective on taste coding in GC. What we know about the topographic organization of GC comes from imaging studies in anesthetized rodents. However, work on various sensory systems suggests that coding in alert animals is radically different from coding under anesthesia. Here, we apply 2-photon calcium imaging to study the representation of taste information and task-related signals in GC of awake mice.  AAV1 virus carrying GCaMP6f was injected into GC and chronic windows made of micro-prisms were implanted above GC. After recovery, mice were water restricted and trained to perform a cued-taste task. For each trial, mice were trained to perform 5 dry licks after an auditory tone (2s, 2k Hz) to receive one of five stimuli (sucrose, NaCl, citric acid, quinine and water) while we monitored neural activity in GC with 2-photon microscopy. We analyzed activity in 872 active neurons from layer 2/3 of 6 mice that had been habituated to tastants. We found that 20.5% (179/872) of the neurons encoded taste identity, 15.8% (138/872) of the neurons were activated by the auditory cue and 8.7% (76/872) neurons were active during licking. For taste coding neurons, half responded exclusively to a single quality, while the other half was tuned to multiple qualities. Taste coding neurons were spatially distributed, with no evidence of spatial clustering. In addition, we also imaged the same portion of GC during Day 1, Day 3 and Day 7 of taste exposure. Altogether, our data suggest that GC encodes taste with spatially distributed patterns of activity and with a mix of narrowly and broadly tuned neurons. 

Sodium Restriction Alters Behavioral And Cortical Responses To Intra-Oral Infusion Of Nacl In Conscious Rats
Alisa M. Goldstein, Christopher A. Guerra, Michael S. King
Stetson University, DeLand, FL, United States

To determine the effect of restricting dietary NaCl on behavioral and neural responses to subsequent NaCl intake, taste reactivity (TR) behaviors and Fos-immunoreactive (Fos-IR) neurons in the gustatory cortex (GC) elicited by intra-oral infusion of 1M NaCl were counted. Nine adult male Wistar rats were used in this study; 4 were placed on a low NaCl diet (Envigo, 0.01% NaCl) for 3 weeks prior to testing while control rats (n=5) were maintained on a normal rodent diet (0.3% NaCl).  Following implantation of intra-oral cannulas and recovery from surgery, the typically ‘aversive’ 1M NaCl was infused (0.233ml/min for 5 min), TR behaviors were videotaped, and then rats were sacrificed and their brains processed for the Fos protein.  Fos-IR neurons in the medial and lateral granular (GI), dysgranular, and agranular insula were counted at 5 positions along the anterior-posterior axis of the GC.  NaCl-restricted rats performed over 4x more ingestive and 28x fewer aversive TR behaviors than control rats (p’s<0.001).  The clearest effects were on tongue protrusions (10x increase in restricted rats) and gapes (22x decrease in restricted rats).  Also, NaCl restriction significantly increased the number of Fos-IR neurons throughout the GC.  Overall, there were 3x more Fos-IR neurons in the GC of restricted than control rats (p<0.001). The biggest differences in the number of Fos-IR neurons were in the rostral and dorsal parts of the GC.  These data indicate that dietary restriction of NaCl changes a largely aversive response to 1M NaCl to an ingestive behavioral response, and increases the number of GC neurons that respond to NaCl, particularly in the rostral and dorsal regions of the GC.  Future studies will attempt to determine the role of GC subareas in the behavioral alterations caused by NaCl restriction.

Comprehensive Modeling Analysis Of The Role Of Cortical Projections To Olfactory Bulb
Christiane Linster1, Leslie Kay2
1Dept. of Neurobiology and Behavior, Cornell University , Ithaca, NY, United States, 2Department of Psychology Institute for Mind and Biology The University of Chicago, Chicago, IL, United States

Olfactory bulb networks integrate sensory information conveyed by sensory neurons with “internal” information conveyed by cortical and neuromodulatory areas. The role of neuromodulatory inputs to the OB has been widely studied experimentally and computationally and coherent ideas about their function exist. In contrast, information conveyed by cortical areas to the OB is sparse but increasing due to new experimental techniques. We here use our fully developed OB-cortex model to systematically investigate the computational impact of cortical to bulbar projections. We include known details of this projection such as target neurons, transmitter released and receptors and investigate unknown parameters such as the distribution of these projections, ratios of inputs to different cell types, timing of inputs with respect to bulbar dynamics. Our model shows that cortical inputs can have strong effects on bulbar signal to noise ratio, bulbar dynamics and bulbar odor representations. These effects depend strongly on cortical dynamics and activation, with cortex receiving olfactory as well as contextual inputs. In addition, when cortical neurons represent contextual inputs, behavioral salience or previously learned odorants, bulbar representations can be strongly modulated by previous experience. The tone and degree of influence cortical inputs have on bulbar processing can be set by learning, network state and previous experience. Funded by DARPA HR0011-18-2-0024

Is Eating Disinhibition Associated With Altered Functional Connectivity Of The Primary Gustatory Cortex With Secondary Gustatory Cortex, Reward Or Memory Regions In Metabolic Syndrome?
Claire Murphy1,2,3, Ekarin E. Pongpipat1, Aaron Jacobson2
1San Diego State University, San Diego, CA, United States, 2University of California, San Diego, San Diego, CA, United States, 3SDSU/UCSD Joint Doctoral Program, San Diego, CA, United States

Metabolic Syndrome (MetS) is a constellation of risk factors (hypertension, fasting hyperglycemia, hypertriglyceridemia, hypoalphalipoproteinemia and abdominal obesity) that together confer increased risk for cardiovascular disease, diabetes and dementia. Habitual disinhibition of eating behavior is strongly associated with weight gain longitudinally.  Here we used 3T functional MRI to investigate whether functional connectivity of the primary and secondary gustatory cortices during hedonic evaluation of sucrose was altered in MetS and whether it was associated with eating disinhibition. Participants were 14 with MetS and 14 without MetS. Disinhibition was operationally defined by the Three-Factor Eating Questionnaire. Functional connectivity (FC) was analyzed using seed-to-whole brain generalized psychophysiological interaction methods. FC of the primary and secondary gustatory cortices was significantly altered in MetS and the relationship between the FC of the primary and secondary gustatory cortices was significantly correlated with eating disinhibition scores. As FC increased, eating disinhibition increased. Furthermore, FC of the frontal operculum and OFC BA47 provided an indirect path as the mediator between MetS risk factors and eating disinhibition. Exploratory results also revealed significantly altered FC of the primary gustatory cortex with brain regions associated with memory and reward in MetS. These findings suggest that individuals with MetS have altered FC of the gustatory cortices that is related to eating disinhibition. We speculate that individuals with MetS may have more difficulty with weight loss interventions because of a lack of inhibition related to altered FC of the primary with the secondary gustatory cortex, in addition to regions associated with memory and reward.

Odor Mixture Representation In Cortical Feedback Projections To The Olfactory Bulb
Joseph D. Zak, Venkatesh N. Murthy
Harvard University, Cambridge, MA, United States

The olfactory bulb not only receives input from the sensory periphery, but also integrates dense top-down information from the piriform cortex. The piriform cortex is thought to be involved in computations related to odor identity, quality, and predictive coding; however, it is unknown to what degree these cognitive aspects of odor processing are transmitted back to the olfactory bulb. We have begun to investigate how projections from the piriform cortex to the olfactory bulb respond to behaviorally relevant odor mixtures. We used multiphoton microscopy to visualize odor responses from cortical axon terminals expressing GCaMP6f. Individual boutons had diverse responses to monomolecular odorants, as well as to complex odor mixtures. The activity of individual boutons >16000 bouton-odor pairs) could be increased or suppressed by stimulation with monomolecular odorants. For nearly all boutons, response polarity was preserved across all responsive odors. We next considered how these feedback projections would respond to odors at different concentrations. For many boutons, we observed strong concentration dependence to the responses, with the highest odor concentration (10%) eliciting the largest positive, as well as negative signals; however, a subset of boutons were concentration invariant. Lastly, we examined bouton responses to odor mixtures containing 2-12 components. Our preliminary analysis points to highly non-linear mixture interactions. We found that the fraction of boutons with enhanced responses increased with the number of mixture components, while the fraction of suppressed boutons remained constant. In summary, complex information about odor composition is broadcast to the olfactory bulb, and ongoing experiments are aimed at dissecting the nature of this information.

Induction Phenomenon After Single And Brief Odor Learning In The Newborn Rabbit
Patricia Duchamp-Viret, Jiasmine Boyer, Marie Vericel, Florian Lavilla, Gerard Coureaud
Lyon Neuroscience Research Center, Bron, *, France

At birth blind and deaf newborn rabbits are totally contingent on their olfactory sense, which in particular drives their nipple searching and oral seizing behavior through the mammary pheromone (MP) emitted by all rabbit mother. At this early stage of life, during which acquisition of novel information contributes to adaptation and survival, any odorant paired with MP only once and for 5 min, is learned and then triggers 24h later the same sucking-related behavior as the MP itself. Here, we aimed at assessing if such an extremely rapid odor learning impacts the peripheral level reactivity, as for the “induction” process (Wysocki et al.1989). To do so, we behaviorally tested neonates and recorded electro-olfactograms (EOG); the animals were either naïve or MP-conditioned to an initially neutral odorant, ethyl maltol (EM). Recordings showed that learning increased EOG amplitudes to EM compared to those recorded in naïve animals. After learning, even if EM was the less concentrated stimulus, it became the most efficacious stimuli in 50% of recordings. This increase was selective for EM, i.e., it was not observed for a control -not learned- odorant, ethyl isobutyrate (EI). In parallel, behavioral testing revealed that the detection performances of EM in conditioned neonates were increased by a factor of 100. Further, the EM learning impacted also and differently EOG and behavioral responses to the EM+EI mixture at two distinct ratios inducing either configural or elemental perception. The results lead us to conclude that the simultaneous increase of peripheral response to EM and its detection performance fulfilled the induction process as defined by Wysocki et al. (1989). These results enrich the scarce data available about this phenomenon in mammals, particularly in neonates.

Posterior Piriform Cortical Modulation Of Odor Fear Memory
Brett S. East1,2, Donald A. Wilson1,2,3,4
1Emotional Brain Institute, Nathan S. Kline Institute, Orangeburg, NY, United States, 2Department of Child & Adolescent Psychiatry, New York University School of Medicine, New York, NY, United States, 3The Neuroscience Institute, New York University School of Medicine, New York, NY, United States, 4Department of Neuroscience and Physiology, New York, NY, United States

Odor perception and hedonics are highly intermeshed at both the behavioral and neural circuit level in humans and non-human animals. This association may in part reflect the fact that the piriform cortex (PCX) is particularly tightly linked with the amygdala. The amygdala targets the posterior PCX (and to a lesser extent the anterior PCX), with the PCX sending reciprocal connections back to the amygdala. The basolateral amygdala (BLA) is required for odor fear learning, and work from our lab has shown that PCX odor responses are shaped by both fear learning and by BLA input. For example, discriminative odor fear conditioning involving both a CS+ and CS- results in odor-specific learned fear responses, as well as narrowing of PCX single-unit odor receptive fields (i.e., enhanced PCX odor acuity). This modification of PCX odor coding may be due to input from the BLA since optogenetic activation of BLA fibers within the PCX can modify single-unit and single-unit ensemble odor responses in anesthetized rodents. However, how the BLA and PCX work in tandem to shape PCX odor coding and hedonics is unknown.  In this work, rats received ibotenic acid lesions of the pPCX (or control) prior to being trained on a differential odor fear task followed by testing for learned freezing 24 hours later. In support of previous work, bilateral pPCX lesions significantly reduced learned, odor-evoked freezing compared to controls suggesting that the pPCX may not only encode odor information but also learned odor associations. Ongoing work is selectively manipulating BLA input to the pPCX during conditioning in order to explore the precise role of communication between PCX and BLA in odor perception and memory.

Memory Mechanisms At Multiple Levels Of Biological Organization
David Levitan, Chenghao Li, Jian-You Lin, Joseph Wachutka, Sacha B. Nelson, Donald B. Katz
Brandeis University, Waltham, MA, United States

Memory is a complex phenomenon that unfolds at multiple levels of biological organization. Fully understanding this complexity requires studying these multiple levels simultaneously. The taste system provides a highly attractive experimental system with which to study the reciprocal causal relationships between gene expression, cellular plasticity, ensemble activity, and behavior. We have developed multiple tools that enable us to address these reciprocal causal relationships in the context of conditioned taste aversion (CTA) in mice. First, using gene profiling of genetically labeled basolateral amygdalar (BLA) projection neurons (which evidence suggests are key to CTA) together with cell-type specific knock-out and electrophysiology, we have discovered genes that simultaneously block CTA learning and alter cellular plasticity of BLA projection neurons. Second, we are examining the impact of these genes on the population dynamics of taste coding—first performing the necessary, basic awake-mouse coding experiments (and demonstrating deep similarities between rat and mouse taste cortical taste processing), and then combining the different approaches to examine the consequences of genetic manipulations that block learning on ensemble coding during CTA learning.

State-Dependent Coding: Licl-Induced State Suppresses Gustatory Cortex Processing
Bradly / T Stone, Donald / B Katz
Brandeis University, Waltham, MA, United States

A large literature addresses how toxicity by way of drug injection (commonly lithium chloride; LiCl) shapes aversive behavior, but few studies have delved into the nature of this powerful state itself. Such states influence an animal’s interactions with its environment, potentially affecting its feeding behavior through modifications of taste perception: an animal that is ill, for instance, is less likely to find food appetitive (a fact that can potentially prolong infirmity by demotivating the animal to ingest nutrient). Here, we report the beginning of an investigation into how the spontaneous network state induced by LiCl specifically impacts taste processing, and how the activity underlying this internal state might support learning. Using extracellular (single-neuron and local field potentials; LFPs) recordings during a passive taste delivery task under two (LiCl-induced sickness and Neutral) conditions, I demonstrate evidence that network state changes induced by internal state manipulations are both represented in the gustatory cortex (GC) and impact taste processing. I show rhythmic activity in the 7-12Hz range emerges at 12 minutes post injection of LiCl and vanishes 6 minutes later, reflecting the onset of malaise, while taste discriminability and palatability correlates (as assessed through ensemble statistics) are significantly reduced in comparison to neutral state. The later suggests the maintenance of internal state impact on cortical activity as they relate to hallmarks of taste processes. These results provide powerful evidence towards the function that an animal’s welfare has on the establishment and maintenance of natural reward valuation and associative effects of stimuli.

Heterogeneity In Ventral Striatal Encoding Of Chemosensory-Driven Reinforcement
Katherine/N Wright1,2, Daniel/W Wesson1,2
1Department of Pharmacology & Therapeutics, University of Florida, Gainesville, FL, United States, 2Center for Smell and Taste, University of Florida, Gainesville, FL, United States

The ability to navigate one’s environment and execute goal-directed behavior is critical for an organism’s survival and requires the coordination of sensory inputs with motivational states. The ventral striatum serves as a site of convergence from cortical and midbrain dopaminergic inputs to evaluate multimodal sensory stimuli and reward valuation, respectively, to inform and select the appropriate behavior. The ventral striatum is comprised of the nucleus accumbens (NAc), well-established for hedonic processing, and the olfactory tubercle (OT), which work from our lab has recently established represents goal-directed behavior and reward value. We thus hypothesized that the OT is capable of encoding reward-seeking behavior and reinforcement similarly to the NAc. To that end, we acquired single-unit activity simultaneously in the OT and NAc as mice engaged in an operant self-administration paradigm. Sucrose and cocaine served as reinforcers to evaluate chemosensory- and non-chemosensory-guided instrumental behaviors, respectively, with outcomes that involved active (oral sucrose) and passive (intravenous cocaine) consummatory phases. In both the NAc and OT we found populations of neurons whose firing patterns were dynamically modulated upon either or both the instrumental response and the consummatory phases. Future work will further profile these populations of neurons to identify neural representations of different aspects of hedonic value and reinforcement.

Role Of Adult-Born Versus Preexisting Neurons In Olfactory Perception In A Complex Olfactory Environment In Mice.
Jeremy Forest1, Laura Chalençon1, Maellie Midroit1, Claire Terrier1, Isabelle Caillé2, Joelle Sacquet1, Claire Benetollo1, Killian Martin1, Marion Richard1, Anne Didier1, Nathalie Mandairon1
1UMR 5292 CNRS CRNL, Lyon, *, France, 23Sorbonne Universités, Université Pierre et Marie Curie Univ Paris 06, Centre National de la Recherche Scientifique UMR8246, INSERM U1130, IBPS, Neuroscience, Paris, *, France

Olfactory perceptual learning is defined as an improvement in the discrimination of perceptually close odorants after passive exposure to these odorants. In mice, simple olfactory perceptual learning involving the discrimination of two odorants depends on an increased number of adult-born neurons in the olfactory bulb, which refines the bulbar output. However, the olfactory environment is complex raising the question of the adjustment of the bulbar network to multiple discrimination challenges. Using habituation/cross habituation task, we found that perceptual learning of one to six pairs of similar odorants led to discrimination of all learned odor pairs. The assessment of adult-born neurons density in the olfactory bulb showed that increasing complexity did not increase adult-born neuron survival but enhanced the number of adult-born neurons responding to learned odorants. To better understand the increased functional recruitment of adult-born neurons with perceptual learning complexity, we looked for associated structural modifications in these neurons. To this aim, we injected lentivirus expressing GFP at P60 and revealed that spine density is increased with increasing complexity. On same animals, lentivirus expressing DsRed was injected at P0 in order to label preexisting neurons (neurons born during the ontogenesis of the granule cell layer in the early post-natal days). Interestingly, only complex learning induced morphological changes in preexisting neurons. Selective optogenetic inactivation of either population performed in freely moving mice confirmed functional involvement of adult-born neurons regardless of the enrichment complexity while preexisting neurons were required for complex discrimination only.

Odor Identification In The Presence Of Novel Backgrounds
Yan Li, Tianyu She, Asiyah Rahman , Asim Ahmed , Jason Wu, Daniel Mogel , Gonzalo Otazu
Department of Biomedical Sciences, College of Osteopathic Medicine, New York Institute of Technology , Old Westbury, NY, United States

Rodents identify odors of interest (target odors) in natural olfactory scenes. Animals can learn to identify odors in the presence of known background odors after multiple exposures. However, it is unclear if an animal trained to recognize an odor in one background would be able to generalize this task in the presence of a different background odor or would require multiple exposures before being able to correctly identify the target odor. In order to test the generalization capability of mice, we presented awake head-fixed mice with target odors in the presence of background odors. We used intrinsic optical imaging to record dorsal glomerular activation patterns to these odor combinations (training set) and used those data to create a linear classifier for detecting the target odors. We tested the learned linear classifier with odor mixtures that included a novel background odor (test set) and found that the linear classifier performance varied between 65% and 90% accuracy for a set of 9 background odors.  We trained 9 head-fixed mice to perform a go/no-go task using the training set. Mice reached 90% performance after 8-10 days of training. We then tested the detection capability using the test set that included the novel odors.  Mice sniff rate increased when they were presented with the novel background odor indicating that the novel background was perceived as a novel odor. Mice correctly identified the target odors with the novel background odors at a rate that was consistent with the imaging data. Mice required an extra sniff to respond to the target odor and mice response times were slower in the novel odor environment compared to the responses to the training set. Our data indicates that animals are able to immediately generalize to novel odor environments.

Diversity In Glutamatergic Input Dynamics Drives Heterogeneous Response Patterns In Olfactory Bulb Mitral And Tufted Cells In Vivo
Andrew K. Moran, Tom P. Eiting, Matt Wachowiak
University of Utah, Salt Lake City, UT, United States

In vertebrates, olfactory sensory neuron (OSN) activation drives glutamatergic excitation of mitral/tufted (MT) cells and juxtaglomerular interneurons in the olfactory bulb (OB). MT cells show diverse temporal response patterns to odorant stimulation, which are thought to arise largely from processing by inhibitory OB circuits. However, this diversity could reflect differences in the temporal dynamics of OSN inputs to MT cells. Here, we imaged odorant-evoked glutamate transients onto MT cell dendrites in the OB of anesthetized and awake mice using the glutamate sensors iGluSnFR and SF-iGluSnFR, allowing us to visualize excitatory synaptic inputs onto MT cells and compare with patterns of postsynaptic activation. We found a surprising diversity in the temporal dynamics of glutamatergic inputs to MT cells, both within and across successive odorant inhalations. First, we observed variable dynamics in the glutamate transients elicited by each inhalation, with latencies, rise-times, and durations varying across glomeruli and odorants. Second, odorants could elicit both adaptation and facilitation of glutamate transients across successive inhalations. Third, we occasionally observed suppression of glutamatergic inputs onto MT cells. To compare glutamatergic inputs and postsynaptic responses we co-expressed SF-iGluSnFR and the red-shifted calcium reporter (jRGECO1a) in the same MT cells and performed dual-color imaging. While suppression in the MT calcium signal sometimes occurred without a corresponding decrease in glutamatergic input, overall we found a strong correspondence between glutamatergic input and postsynaptic response patterns. These results suggest that diversity in glutamatergic inputs onto MT cells plays a large role in shaping the temporal patterning of activity among OB output neurons.

Defining The Functions Of Olfactory Bulb Processing Via Comparison Of Input And Output: Adaptation
Douglas A Storace1,2, Lawrence B Cohen2,3
1Florida State University, Tallahassee, FL, United States, 2Yale University, New Haven, CT, United States, 3KIST, Seoul, *, Korea

Humans and other animals exhibit adaptation to odorants. It remains unclear whether the olfactory bulb, the brain structure that mediates the first stage of olfactory information processing, participates in generating this perceptual adaptation. Olfactory bulb glomeruli are regions of neuropil that contain input and output processes; olfactory receptor neuron nerve terminals (input) and mitral/tufted cell apical dendrites (output). Differences between the input and output of a brain region define the function(s) carried out by that region. We compared the activity signals from the input and output to repeated odor stimulation across a range of odorant concentrations. Repeated odor stimulation of the same concentration resulted in a decline in the output maps, while the input remained relatively stable. These results suggest that the mammalian olfactory bulb may participate in the perception of adaptation. This approach may be useful for understanding the role of the olfactory bulb in other olfactory perceptions, and should also be useful for determining the input-output transformation in other regions of the mammalian brain.

The &Ldquo;Hard Problem&Rdquo; Of Olfaction: Odor Identification From Strongly Occluded Sensory Inputs In A Neuromorphic Olfactory Bulb Circuit
Nabil Imam1, Thomas A. Cleland2
1Neuromorphic Computing Laboratory, Intel Labs, Santa Clara, CA, United States, 2Dept. Psychology, Cornell University, Ithaca, NY, United States

The recognition of meaningful odors encountered within complex and unpredictable chemical environments constitutes the “hard problem” of olfactory neuroscience.  The mammalian olfactory system learns new odors rapidly, exhibits negligible interference among odor memories, and identifies known odors under highly challenging conditions.  The mechanisms by which it does so are unknown.  We here present a general theory for odor learning and identification under noise in the early olfactory system, and demonstrate its efficacy using an olfactory bulb model instantiated in adaptive neuromorphic hardware.  As with biological olfaction, the spike timing-based algorithm utilizes localized computations and resists catastrophic forgetting.  Spike timing-dependent plasticity is employed iteratively over sequential gamma-frequency packets to construct odor representations from the activity of chemosensor arrays mounted in a wind tunnel. Learned odors then are reliably identified even in the presence of strong destructive interference. Noise resistance is enhanced by neuromodulation and contextual priming.  Lifelong learning capabilities are enabled by adult neurogenesis.  The algorithm is applicable to any signal identification problem in which high-dimensional signals are embedded in unknown backgrounds.

Imaging During Odor-Guided Behavior With A Novel, Wide Field-Of-View Miniature Fluorescence Microscope
Daniel P. Leman1, Ichun A. Chen1, William W. Yen1, Lewis N. Perkins1, William A. Liberti III2, Kivilcim Kilic1, Alberto Cruz-Martin1, Timothy J. Gardner1,3, Timothy M. Otchy1, Ian G. Davison1
1Boston University, Boston, MA, United States, 2University of California, Berkeley, Berkeley, CA, United States, 3Neuralink, San Francisco, CA, United States

Odors provide a rich set of environmental cues that guide ethologically relevant behaviors such as localization, navigation, and social interactions with both conspecifics and predators.  Many, if not all, of these contexts require animals to freely explore and actively sample their surroundings in both space and time. The development of miniaturized, head-mounted fluorescence microscopes, or “miniscopes”, combined with advances in genetically encoded Ca2+ indicators, has allowed recording of activity of large neural populations in small animals during diverse naturalistic behaviors. However, current miniscope systems rely on small diameter gradient-index optics that restrict their effective imaging areas to less than 1 mm2. Here, we present an enlarged field-of-view miniscope providing optical access to brain areas encompassing approximately 7-8 mm2, an order of magnitude increase over prior systems for freely behaving mice. Our optical design provides resolution of approximately 10 μm, sufficient for resolving individual neurons.  Our low-cost, open source system is based on a 3D-printed housing and off-the-shelf components, and is readily modifiable for different experimental demands.  Here we use the wide-area miniscope to image sensory maps in the main olfactory bulb of mice engaged in an odor-based localization task, revealing both spatial patterns of glomerular responses and temporal dynamics of sniffing-coupled activity. This system promises to help provide insight into the strategies that underpin natural sensory behaviors.  More broadly, it will also allow visualization of extended cortical regions, providing a valuable approach for probing large-scale cross-area interactions in naturalistic environments.

Decoding Olfactory Stimulus Strength From Olfactory Bulb Lfp Oscillations
Justin T. Losacco, Diego Restrepo
University of Colorado Anschutz Medical Campus, Aurora, CO, United States

The perception of odor concentration is vital for survival. Since increased concentration reduces firing latency for mitral cells in the olfactory bulb (OB), firing phase with respect to the low frequency oscillation (LFO: respiration, theta local field potential) may convey stimulus strength. This signal can be read out via single cell firing, through aggregate neuronal activity patterns in the local field potential (LFP), and through the interaction between these phenomena—through spike-field coherence. While the representation of stimulus strength in mitral cell firing has been studied in vitro, markedly less is known about how the network of principal cells in OB conveys this information. Here, I implanted tetrodes into the mitral cell layer of the dorsomedial OB of C57BL/6 mice. Single-unit activity and the LFP were recorded while the mice performed two variants of the behavioral go no-go task, discriminating between odor identity—and separately—odor concentration. All mice learned both tasks within a few days of training. LFP power (all bands) increased for rewarded stimuli and decreased for unrewarded stimuli over task acquisition in both paradigms (identity and concentration). In the concentration task, LFP power correlated with the rewarded odors irrespective of concentration. Phase amplitude coupling (PAC), or the relationship between the oscillatory phase of the LFO and the power of a higher frequency gamma oscillation (from coherent mitral cell firing) was stronger for the identity task than the concentration task. Additional work using discriminant analysis will determine whether LFP power or PAC are able to decode which stimulus was presented in both the identity and concentration paradigms.

Specific Antagonism Is Prominent In Odorant Receptor-Based Combinatorial Coding
Patrick Pfister, Barry J. Evans, Casey Trimmer, Randy Arroyave, Mushhood Sheikh, Matthew E. Rogers
Firmenich Incorporated, Corporate Research and Development, Plainsboro, NJ, United States

Little is known about the role of odorant receptor (OR) antagonism in shaping the combinatorial code upon complex odor presentation. Here, we sought to investigate antagonism and its pharmacology using an in vitro high-throughput screening platform.  We first deorphaned the mouse receptor Olfr743 through single-cell transcriptomics of indole- and skatole-activated olfactory sensory neurons (OSNs). Subsequent phylogenetic analyses revealed the existence of six paralogous receptors sharing over 78% amino acid identity and an additional six members of the closest outgroup ranging over 56% identity. We first characterized the in vitro response profile of these ORs with chemical indole analogs and revealed partially-overlapping but distinct agonist activation profiles. We then used a set of 800 chemically diverse perfumery ingredients to probe the inhibition profiles of a subset of 10 indole-responsive ORs (including all Olfr743 paralogs) in the presence of indole and observed distinct receptor-specific inhibition profiles. 422 compounds antagonized the activity of at least one OR. We found the number of antagonists and the overlap in antagonists varied widely among ORs; furthermore, in some cases, a compound acted as an activator for one OR and an antagonist for another. Such distinct activation and inhibition profiles between paralogous genes supports the view that OR gene diversification leads to receptive range diversification rather than functional redundancy for both agonism and antagonism. Taken together, we conclude that, even within a family of closely related receptors, antagonism is widespread, likely to play a prominent role in olfactory peripheral computation and may serve to expand the encoding capacity of the system.

Altered Dynamics Of Glucocorticoid Receptor &Ndash; Chaperone Complexes In Neuroepithelial Cells Of Patients With Depression
Karin Borgmann-Winter1,2, Sarah Jefferson1, John O'Reardon1, Nancy Rawson3, Olivier Berton1, Chang-Gyu Hahn1
1University of Pennsylvania, Philadelphia, PA, United States, 2Children's Hospital of Philadelphia, Philadelphia, PA, United States, 3Monell Chemical Senses Center, Philadelphia, PA, United States

Background: As the only neural cell type available from living individuals without genomic reprogramming, olfactory neuroepithelial cells represent a uniquely valuable tool to dissect the molecular pathophysiology of neuropsychiatric disorders. Our laboratory has previously used these cells in studies of bipolar disorder and schizophrenia (Borgmann-Winter 2015, 2016)   Objective: To examine molecular alterations in glucocorticoid receptor (GR) chaperone complex dynamics in the pathophysiology of major depressive disorder (MDD)   Method: We examined GR – chaperone interactions in olfactory neuroepithelial cells derived from 15 matched pairs of MDD subjects and healthy controls for nuclear translocation of glucocorticoid receptor (GR translocation), GR-chaperone interactions and their inter-relationships.  Results: GR translocation, a key step for glucocorticoid signaling, was strikingly reduced in the MDD group compared to control. This is not due to dysregulation of the expression of the glucocorticoid receptor or its chaperones at the mRNA or protein levels in the patient group. Interestingly protein interactions of GRs with FKBP51, which serves as a negative regulator of glucocorticoid signaling, were increased in the MDD group. In healthy subjects, FKBP51 in GR complexes showed a robust and positive correlation with GR translocation (R2= 0.88), suggesting a homeostatic balance between the two parameters. MDD subjects showed no significant correlation between FKBP51 and GR translocation.  Conclusion: These results provide the first direct evidence for dysregulated GR translocation and GR-chaperone interactions in neural cells of MDD subjects. This study indicates that OE cells derived from patients with neuropsychiatric illnesses can serve as a cellular model to study associated stress signaling.  

Methimazole-Induced Injury Alters Levels Of Expression Of Engulfment Proteins
Rudy T. Chapman, Diego J. Rodriguez-Gil
East Tennessee State University, Johnson City, TN, United States

The olfactory system has the unique ability to regenerate throughout life, which allows the sense of smell to be maintained in spite of the high death rate of olfactory sensory neurons. When a sensory neuron from the olfactory epithelium dies, another sensory neuron is born to take its place and extends an axon to establish synaptic contact in the olfactory bulb. In addition to regeneration due to normal turnover, the olfactory system is also able to regenerate after an injury in which a portion or even the entire olfactory epithelium is removed. An established model of injury to the olfactory system is by chemical ablation through an acute injection of the drug methimazole. An element of regeneration after an injury that is of interest is the mechanism by which cellular debris from ablated neurons is removed. When the olfactory epithelium is removed due to an injury, the cell bodies of the neurons in the epithelium are removed but their axons remain. The axonal debris from the ablated neurons must be removed in a way that minimizes inflammation in order to allow for extension of new axons to the olfactory bulb. In vitro and during development this role has been attributed to the olfactory ensheathing cells, yet what happens after injury or the mechanism involved in the process have not been identified. In order to understand how cellular debris is removed after injury, our lab has studied the engulfment proteins Jedi1, Gulp1, and Megf10 using RT-qPCR. We found specific temporal expression profiles from olfactory bulbs at 3, 14, and 21 days post injury that start to shed a light into the role of these proteins in the engulfment process. Changes in expression of engulfment proteins after injury will help in understanding the mechanisms by which neuronal debris is cleared after an injury.

The Neuroplastic Effect Of Olfactory Training To The Recovery Of Olfactory System In Mouse Model
Boo-Young Kim1, Sang-uk Lee2
1Catholic university, Otorhinolaryngology department, Uijeoungbu, *, Korea, 2catholic university, Orthopedics, Incheon, *, Korea

Objective: Several studies have reported the benefits of olfactory training (OT) in the olfactory nervous system of mouse models. Therefore, next-generation sequencing was performed to evaluate the effects of OT on mRNA sequencing in the olfactory area. Subjects and Methods: Mice in each group were administered 300 mg of 3-methylindole per kg of mouse weight. The olfactory function was evaluated by a food-finding test once a week. The olfactory neuroepithelium was harvested for histologic examination and protein analysis. Subsequently, data analysis, gene ontology and pathway analysis, quantitative real-time polymerase chain reaction of mRNA, and western blot analysis were conducted. Results: Mice were divided into four groups according to treatment. Control, anosmia, training, and steroid group mice resumed food finding. Olfactory Maker Protein, olfr1507, ADCY3, and GNAL mRNA expression was higher in the olfactory neuroepithelium of OT than anosmia group mice. In total, 26,364 mRNAs were differentially expressed. Comparison of the results of OT versus anosmia revealed that ADCY8,10, GFAP, NGF, NGFR, GFAP, and BDNF mRNAs were upregulated in the gene ontology. Conclusions: OT improved olfactory function, as indicated by the food finding test. OT improved the olfactory recovery time to stimulate olfactory nerve regeneration. OT might initially stimulate the olfactory receptor, followed by neurogenesis. Steroid therapy and OT operate under completely different mechanisms in the upregulated gene study. These results indicate that OT might be one of the future modalities for treating olfactory impairment.

Olfactory Function After Mild Traumatic Brain Injury In Children &Ndash; A Longitudinal Study
Theresa Thieme, Valentin Schriever
Abteilung Neuropädiatrie, Dresden, *, Germany

Aim: An association between traumatic brain injury (TBI) and olfactory dysfunction has been described in previous studies. However, predictive markers for olfactory dysfunction after TBI in children are not well examined. Aim of the study was to examine olfactory function after mild TBI in a longitudinal study design in children and to identify predictive markers for olfactory dysfunction after TBI. Material and methods: A total of 151 children (75 patients after mild TBI, 76 healthy children as control group (age and sex matched)), age 6-16 years were included. Patients were fist tested on average at 1.8±0.9 days after TBI (T1). The follow-up testing was conducted after 12 months (T2). Olfactory function was assessed using an olfactory threshold and the “U-Sniff” odor identification test.    Results: Overall patients scored worse on olfactory threshold test compared to controls (p<0.01). The difference just misted significance at T1 testing (p=0.051) and still showed a strong trend at the one-year follow-up (T2) (p=0.088). No significant difference between patients and controls was found regarding odor identification. 47% of patients scored below the 10th percentile on olfactory threshold at T1 compared to 16% of the control group (χ2=6.51, p=0.01). This difference showed still a strong trend at T2 (χ2=3.22, p=0.07). None of the TBI symptoms (emesis, loss of consciousness amnesia, location of TBI) showed to have a significant predictive value regarding olfactory dysfunction at T1 or T2. Conclusion: Even mild TBI showed to be associated with olfactory dysfunction in children. Although olfactory function improved in patients, the difference was still measurable after one year. No predictive marker for developing olfactory dysfunction after mild TBI could be identified.

Alzheimer'S Disease & Olfaction: Preliminary Results Towards An Early Diagnosis
Rayane Zahal1, Dominique Petit1, Nadia Gosselin1, Julie Carrier1, Johannes Frasnelli1,2
1University of Montreal, Montreal, QC, Canada, 2Université du Québec à Trois-Rivière, Trois-Rivière, QC, Canada

Alzheimer’s Disease (AD) is a neurodegenerative disease that affects cognitive function and behavior. It is the most frequent type of dementia among old people. Olfactory impairment appears many years before cognitive symptoms in AD patients, but its exact manifestation is still unclear. AD is a continuum with three distinct stages: preclinical, Mild Cognitive Impairment (MCI) and dementia.The goal of this study is to define specific patterns of olfactory impairment in the MCI phase. A better understanding of AD would bring us closer to developing therapeutic approaches to stop or slow down its progression in early stages. Five different olfactory tasks (odor identification, discrimination, recognition, threshold, and a cognitive modulation task to assess the impact of label on odor perception) are administered to three groups 1) amnestic MCI patients; 2) non-amnestic MCI patients; 3) controls Neuropsychological assessment include: memory and learning; language; attention and executive function; and visuospatial functions. Participants are followed up after 1.5 year. Three hypotheses shape this study: 1) Healthy participants have a better performance in olfactory tasks compared to MCI patients. 2) Non-amnestic MCI patients perform better than amnestic MCI patients in odor identification and recognition. 3) Participants who demonstrate impairment in odor recognition and identification tasks in T1, show a significantly greater cognitive decline/ conversion rate in T2. Testing and data acquisition are ongoing and preliminary results are presented.

Concentration Change Processing In The Mouse Olfactory Bulb
Morgan Brown, Philip Parker, Avinash Bala, Richard Taylor, Roma Shusterman , Matt Smear
University of Oregon, Eugene, OR, United States

All sensory modalities must track how stimuli change over time. To accomplish this, many neurons in sensory systems respond preferentially to dynamic stimuli, thus enhancing temporal contrast. Given the ethological importance of odor concentration change (ΔC) to tracking an odor, the olfactory system may also accentuate temporal changes. While dynamic stimulation is standard in studies of other sensory modalities, studies of mammalian olfaction have traditionally used square stimulus pulses of the same concentration. To provide dynamic odor stimuli, we developed an odor delivery system that can change odor concentration within the typical inhalation timeframe via air dilution manifold. This enables not just fast onset of the stimulus, but fast concentration changes on the timescale of individual sniffs. Importantly, these step-function stimuli reach steady state by the time the mouse begins to inhale, making them reproducible from trial to trial. Using electrophysiological recordings, we have previously shown  that neurons of the mouse olfactory bulb explicitly encode DC. To understand the spatial distribution and morphological identity of DC sensitive neurons, we have performed calcium imaging, utilizing the ability of two photon imaging to reveal the spatial arrangement of imaged neurons. Using standard intersectional viral/transgenic techniques, we express GCaMP 7f in mitral and tufted cells of the olfactory bulb. We then image these neurons through chronically implanted windows on the dorsal surface of the bulb. Thus we can visualize ΔC-sensitive neurons, a putative cell type which may contribute to odor tracking.

Daspei Imaging: In Search Of Earthworm Chemoreceptors Using A Live Cell Dye
Eui Y Kim, Eileen M Reed, Glen S Marrs, Cecil J Saunders, Wayne L Silver
Wake Forest University, Winston-Salem, NC, United States

Earthworms play an important role in soil ecology and agriculture. The number of earthworms in an area is commonly used to assay a soil ecosystem’s health. A standard means of sampling earthworm  populations is the application of allyl isothiocyanate (AITC) to expel earthworms from an area. Despite AITC being a common earthworm expellant, how these animals detect AITC and other chemicals is poorly understood. We report here the use of DASPEI, a dye that fluorescently labels electrically active cells, to measure activity in epidermal cells of Eisenia hortensis after stimulation by AITC and other compounds. The epithelium of the second segment of three earthworms per concentration was imaged using a confocal microscope. In each worm, three regions of interest were selected to avoid setae and thresholded at 3 times the maximum background. Worms treated with AITC yielded significantly higher fluorescence compared to worms treated with DASPEI and vehicle alone (p<0.01, ANOVA) and in a dosage-dependent manner (1mM vs. 10mM, p<0.01, ANOVA) while no significance was noted between the PBS and 10% mineral oil. In addition to AITC, a significant difference was noted for 500mM potassium chloride (p<0.001, ANOVA) but not for 16mM capsaicin (p=0.0857, ANOVA). Two fungal compounds, ethyl hexanoate and ethyl pentanoate, previously reported as being appetitive were tested with only 25mM ethyl pentanoate (p<0.001, ANOVA) showing significance. From various neurotransmitters, only 100µM octopamine showed significance(p<0.01, ANOVA). Our results provide support for a novel method of imaging chemoreceptor cell activity. We demonstrated that earthworm epidermal cells respond to a variety of chemical stimuli. This is an early step in our efforts to identify how earthworms detect chemicals in their environment.

Loss Of Arl13B In Olfactory Sensory Neurons Leads To Age Related Olfactory Impairment
Jordan C. Moretta1, Warren W. Green1, Kirill Ukhanov1, Julia C. Habif1, Chao Xie1, Lian Zhang1, Cedric R. Uytingco1, Jeffrey R. Martens1
1University of Florida, Gainesville, FL, United States, 2University of Florida, Gainesville, FL, United States, 3University of Florida, Gainesville, FL, United States, 4University of Florida, Gainesville, FL, United States, 5University of Florida, Gainesville, FL, United States, 6University of Florida, Gainesville, FL, United States, 7University of Florida, Gainesville, FL, United States, 8University of Florida, Gainesville, FL, United States

Cilia are small, microtubule-based organelles found on most cell types, which play a vital role in numerous cell functions. In primary cilia, the small GTPase Arl13b is known to regulate ciliogenesis, protein trafficking, and signaling pathways. Mutations of ARL13b can have deleterious effects leading to human ciliopathies such as Joubert syndrome. The role of Arl13b in olfactory cilia is unknown. As such, it is also unknown if Joubert syndrome shows a penetrance into the olfactory system. Therefore, our objective is to elucidate the function of Arl13b in olfactory cilia. ARL13b is expressed during post-natal development of the OE in maturing OSNs but is dramatically reduced in OMP-positive OSNs. However, the penetrance of OMP-specific knockout of ARL13b (Arl13bosnKO) in mice is observed after this window and increases with age. In 8-week old Arl13bosnKO mice both the cilia number and length were significantly decreased resulting in impaired odor sensitivity measured by EOG. Concomitantly, in the OB of 8-week old Arl13bosnKO mice we found a significant decrease of individual glomeruli size as well as a nearly 4-fold loss of TH staining with a concentric gradient of intensity for OMP immunofluorescence. These findings suggest a previously unknown function of Arl13b, expressed during a critical time window early in the development of the OE. At 6 months of age this phenotype was exacerbated by a reduction in OE thickness, number of mature OSNs, and TH bulb staining in Arl13bosnKO mice suggesting severe neurodegeneration as well. These results indicate that Joubert syndrome patients may have an exacerbated olfactory deficit with aging. Further studies will target an exact role of Arl13b in the olfactory system and ultimately define a viable strategy for gene therapy of Joubert syndrome patients.

Olfactory Activity Selectively Regulates The Neurogenesis Of A Subset Of Olfactory Sensory Neurons
Stephen W. Santoro, Carl J. van der Linden, Kelci R. Germann, Pooja Gupta, Ashraful I. Bhuiya
Neuroscience Program and Dept. of Zoology and Physiology, University of Wyoming, Laramie, WY, United States

Olfactory sensory neurons (OSNs) are one of a small number of neuron types that turn over throughout life in mammals. OSN turnover is thought to function primarily to replace OSNs that are damaged as a result of exposure to environmental insults. Newborn OSNs are thought to stochastically express just one odorant receptor (OR) allele from among hundreds present within a typical mammalian genome. Using gene expression analysis of the mouse olfactory epithelium (OE) in combination with RNA fluorescent in situ hybridization (RNA-FISH), we found that olfactory deprivation on one side of the OE via unilateral naris occlusion causes significant differences in the number of OSNs that express particular ORs on the two sides of the OE. We hypothesized that these differences might be due in part to selective changes in the neurogenesis rates of OSNs that express these ORs. To test this hypothesis, we developed a method involving EdU detection combined with RNA-FISH to quantify the neurogenesis rates of OSNs that express specific ORs. Using this method, we found that olfactory activity deprivation causes selective and significant decreases in the neurogenesis rates of OSNs that express a particular subset of ORs, while not affecting intermingled OSNs that express other ORs. Moreover, we found that OSN subtypes that exhibit activity-dependent neurogenesis are not more active than those whose neurogenesis is activity-independent, indicating that high levels of olfactory activity are not sufficient to cause particular OSN subtypes to exhibit activity-dependent neurogenesis. These findings reveal a previously unknown type of plasticity within the olfactory system that may have fundamental implications for how the system develops and changes based on experience.

Single Cell Transcriptome Analysis Of Olfactory Sensory Neurons
Delia Tomoiaga3, Raena Mina1, 2, Eugene Lempert1, 2, Christopher E Mason3, 4, Paul Feinstein1, 2
1Hunter College, CUNY, Department of Biological Sciences, New York, NY, United States, 2Graduate Center of CUNY, Biochemistry, MCD, and CCP Programs , New York, NY, United States, 3Weill Cornell Medicine, Department of Physiology and Biophysics, New York, NY, United States, 4Weill Cornell Medicine, Tri-institutional Training Program in Computational Biology and Medicine, New York, NY, United States

  The olfactory sensory neurons of the olfactory system in mammals detects odors by an enormous superfamily of G-protein coupled receptor genes, aptly named as odorant receptors (ORs) genes.  This gene family number 1500 genes in the mouse and about 1000 in humans, but not all of the ORs produce functional proteins. In the mouse, the functional repertoire is believed to number around 1200 genes. The lack of selective pressure on these genes provides for the possibility that each allele of each gene encodes a distinct protein. Thus, the repertoire of functional OR alleles could be as high as 2400. The biology of the olfactory system is set up in such a way that the expression of one functional OR allele inhibits the expression of any other OR allele.  This functional OR allele also provides the axons of their neurons the ability to project homotypically into homogeneous glomeruli in the olfactory bulb. As such, each of the 2400 OR alleles, represented by approximately ~4000 neurons on average, send projections to the olfactory bulb.  A few years ago, we published the MouSensor technology1, which increases the representation of a given cloned OR allele such that it is represented by 500,000 or more neurons. We are using this technology to characterize the transcriptome of many neurons that have selected the same OR allele for expression. Our preliminary mRNA analysis suggests that MouSensor OR transgene expressing neurons only express the MouSensor OR", which is consistent with our previous axon guidance data.                                                                                  1MouSensor: A Versatile Genetic Platform to Create Super Sniffer Mice for Studying Human Odor Coding. (2016) Charlotte D’Hulst, Raena B. Mina, Zachary Gershon, Sophie Jamet, AntonioCerullo, Delia Tomoiaga, Li Bai, Leonardo Belluscio, Matthew Rogers, Yevgeniy Sirotin, and Paul Feinstein. Cell Rep. 2016 Jul 26;16(4):1115-25. doi: 10.1016/j.celrep.2016.06.047. Epub 2016 Jul 7.

Targeted Transcriptomics Of Olfactory Receptors For High-Throughput Mapping Of Olfactory Bulb Glomeruli
Kevin Zhu1, Justin Silverman1, Shawn Burton2, Matt Wachowiak2, Hiroaki Matsunami1
1Duke University, Durham, NC, United States, 2University of Utah, Salt Lake City, UT, United States

The formation of position-stereotyped, receptor-specific glomeruli in the olfactory bulb (OB) presents a complex wiring problem due to the expansive olfactory receptor (OR) repertoire and expression of a single OR in olfactory sensory neurons (OSNs) scattered in the nasal epithelium. Identifying the glomeruli corresponding to a specific OR and overall organization of OR projections is critical to understanding how receptor signals are translated into specific spatio-temporal responses in the OB. Since 1994, efforts have identified mouse OB glomeruli for ~3% of the 1100 ORs. We aim to generate a comprehensive map of mammalian OR glomeruli via a novel high-throughput approach that determines the OR identity of a glomerulus by sequencing low-abundance OR transcripts in the axon termini of OSNs. We first identified the ORs present in the set of dorsal glomeruli viewed in functional imaging studies through dissection, cDNA synthesis, and enrichment of OR and TAAR transcripts using target capture probes. Differential expression analysis of this sample and the remainder of the OB found 86 ORs and 11 TAARs enriched, with 94% of these ORs expressed in the dorsal olfactory epithelium and no TAARs enriched in the remainder. Spatial information for 909 ORs was attained by targeted sequencing of 100µm serial sections from individual OBs along the coronal, sagittal, and horizontal planes. We found reproducibly unique sets of OR transcripts enriched in each section, suggesting OR identities of glomeruli within each section. A Bayesian reconstruction method will help determine the 3D position of each OR’s glomeruli. Establishing an OR-to-OB map will provide a framework for integrating peripheral ligand-OR deorphanization assays with OB odor representations, a key resource for cracking the olfactory code.

Analytical Identification Of Stress Odors From Human Breath
Christopher Maute1, Pamela H. Dalton1, Jason Eades1, Wesley Haskins1, George Preti1, 2
1Monell Chemical Senses Center, Philadelphia, PA, United States, 2Department of Dermatology, School of Medicine, University of Pennsylvania, Philadelphia, PA, United States

When a stress response is triggered in humans, characteristic physiological changes occur as a result of the increased production of stress-related hormones.  These stress-related hormonal changes create alterations in the salivary flow and composition, which consequently upregulate production of volatile organic compounds (VOCs) notably, volatile sulfur compounds and perhaps oxygenated compounds related to oxidative stress. Thus, we hypothesized that the volatile composition of exhaled breath would be influenced by stress, with important contributions from the oral cavity—a contribution that is often overlooked by investigators examining breath VOCs. To test our hypothesis, we collected breath and saliva samples from human subjects before and after employing the Trier Social Stress Test (TSST) to induce psychological stress and analyzed the samples for VOC’s.  Three VOCs were found to be significantly elevated by stress in the breath samples, but not the saliva: acetone, isoprene and dimethylsulfide.  Further, the increases in these breath-born biomarkers seem to rely on different aspects of the stress response, with isoprene and dimethylsulfide being significantly correlated with cortisol levels.

Behavioral And Neurophysiological Mechanisms Underlying Responses To Olfactory Volatility In Autism
Valentina Parma1,2, Michele Furlan2, David N Top3, Kevin Stephenson3, Mikle South3
1William James Center for Reseach, Lisbon, *, Portugal, 2International School for Advanced Studies, Trieste, *, Italy, 3Brigham Young University, Provo, UT, United States

Odor stimuli are naturally volatile and dynamic stimuli, and constitute a test-bed for the volatility of sensory environmen often overestimated by adults with autism spectrum disorder (ASD). At the behavioral level, overestimating the change in sensory environment should correspond to longer times and reduced accuracy in discrimination tasks. At the neural level, this behavior is expected to be grounded in the functioning of areas known to preferentially encode features (e.g., quality) and sensitive to repeated exposures (i.e., piriform cortex). We assessed these hypotheses by asking to 20 adults with ASD (8F) and 14 (8F) typical controls (TD) to participate to a discrimination task and an fMRI a cross-adaptation task. Participants smelled 40 pairs of odorants that could share the same perceptual quality (e.g., minty/floral) or the same chemical group (e.g., ketones/alcohols) to decide whether the two odorants were different. As expected, individuals with ASD are slower than TD in discriminating the same quality, and as slow as TD in discriminating different qualities. Discriminating chemical group takes longer in ASD. The accuracy for the different odor qualities in the ASD group is reduced compared to the TD group. Whole-brain and representational similarity analyses, with specific interest in the piriform cortex, are ongoing. Preliminary data suggest suppression of activity following the presentation of two stimuli sharing one feature in the TD but not in the ASD group. The odor­ evoked activity in posterior piriform cortex significantly decreased (cross­-adapted) in response to qualitatively similar, but not to chemically similar, odorant pairs in TD, but not in ASD. Our findings offer novel insights into the behavioral and physiological mechanisms underlying sensory volatility in ASD.

Body Odor Disgust Sensitivity Is Associated With Prejudice Towards A Fictive Group Of Immigrants
Marta Zakrzewska1, Jonas Olofsson1, Torun Lindholm2, Anna Blomkvist2, Marco Tulio Liuzza3
1Gösta Ekman Laboratory, Stockholm University, Stockholm, *, Sweden, 2 Stockholm University, Stockholm, *, Sweden, 3"Magna Graecia" University of Catanzaro, Catanzaro, *, Italy

Why are certain individuals persistent in opposing immigration? The behavioral immune system framework implies that a psychological mechanism, which adapted to detect and avoid pathogen threats, is also reflected in contemporary social attitudes. Moreover, prejudice towards outgroups might be partially driven by implicit pathogen concerns related to dissimilarity of these groups’ hygiene and food preparation practices. Disgust, a universal core emotion supposedly evolved to avoid pathogen threats, as well as olfaction, both play a pivotal role in evoking disgust. In an online study (N = 800), we investigated whether individual differences in body odor disgust sensitivity (BODS) correlate with negative attitudes towards a fictive refugee group. Participants completed questionnaires regarding their body odor disgust sensitivity, prejudice towards a fictive refugee group and attitudes towards immigrants in general. We used a Bayesian approach for parameter estimation and hypothesis testing (i.e., the Bayes factor) and tested our hypothesis via Bayesian regression models. Additionally, we used structural equation modelling (SEM) to confirm our theoretical model. The data analysis plan and hypotheses were preregistered on the Open Science Framework (OSF, https://osf.io/ fsbna/). Results show that body odor disgust sensitivity is associated with xenophobia: BODS was positively associated with negative attitudes towards the fictive group. This relationship was partially mediated by perceived dissimilarities of the group in terms of hygiene and food preparation. Our finding suggests prejudice might be rooted in sensory mechanisms.

The Gc-D/Necklace Olfactory Subsystem Promotes The Acquisition Of Odor Preferences Independent Of Consummatory Behavior
Arthur D. Zimmerman1,2, Steven D. Munger1,2
1University of Florida Center for Smell and Taste, Gainesville, FL, United States, 2University of Florida Department of Pharmacology and Therapeutics, Gainesville, FL, United States

The guanylyl cyclase-D (GC-D)/necklace glomeruli (NG) olfactory subsystem mediates olfactory-dependent social learning in rodents, as seen during the social transmission of food preference (STFP). During an STFP, an “observer” mouse associates the detection of a novel (“demonstrated”) odor by canonical olfactory sensory neurons (OSNs) with coincident detection of a social chemostimulus specific for GC-D-positive (GC-D+) OSNs (e.g., carbon disulfide, uroguanylin (UG), guanylin), resulting in the acquisition of a preference for food containing the demonstrated odor. However, STFPs have routinely been assessed in the context of a choice between differently odored foods. Therefore, it was unknown whether mice are forming a consummatory preference or if the GC-D/NG subsystem mediates the acquisition of an odor preference. Here, we use a two-port odor preference apparatus to measure odor preference ratios (PRs, time spent sampling the demonstrated odor/total time spent sampling both odors). We found that Gucy2d+/+ or +/- mice, but not Gucy2d-/- mice, show a significant preference for the demonstrated odor after olfactory sampling of a novel odor (cocoa, 2%; or cinnamon, 1%) plus a GC-D+ OSN stimulus [50 nM guanylin: PR=0.66 +/- 0.03 (+/+, +/-), 0.47 +/- 0.04 (-/-); p<0.05; 50 nM UG: 0.66 +/- 0.01 (+/+, +/-), 0.44 +/- 0.02 (-/-); p<0.05). Gucy2d+/+ or +/- mice also show a significant preference for the demonstrated odor when exposed to a live demonstrator [0.70 +/- 0.03 (+/+, +/-), 0.48 +/- 0.02 (-/-); p<0.05]. Preferred odors elicited more nose pokes, but there were no differences in bout duration between odors or total investigation time between genotypes. Our results indicate food preferences observed during an STFP result from the acquisition of a GC-D-dependent odor preference.

Ghrelin Alters Fatty Acid Signaling In Taste Cells
Ashley N. Calder1,2, Naima S. Dahir1,2, Tian Yu3, Timothy A. Gilbertson2
1Burnett School of Biomedical Sciences, University of Central Florida, Orlando, FL, United States, 2Department of Internal Medicine, College of Medicine, University of Central Florida, Orlando, FL, United States, 3Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, United States

Ghrelin has long been implicated in energy homeostasis and is thought to regulate caloric consumption. Secreted by gastric emptying, circulating ghrelin has been shown to work in diverse physiological pathways including caloric intake, glucose regulation, and lipid storage. Previous data have shown that ghrelin and its receptor are located in the taste system. Mice lacking ghrelin have a decreased caloric intake and altered lipid preferences (Cai et al., PLoS One 8(10), 2013). To date, limited research has explored the role of ghrelin in fat taste. Previous work in our lab demonstrated high levels of co-localization between growth-hormone secratogue receptor (GHSR), a ghrelin receptor, and markers for Type II cells, the main cells responsible for fat taste transduction. The current study is aimed at evaluating the functional role of ghrelin in fat taste using ghrelin-null mice and WT mice. To date, we found that taste cells from ghrelin-null mice have functionally altered taste responses to fatty acids (FA) as illustrated by calcium imaging than WT mice. GPR120 and CD36, key components in the initial receptive events in the FA taste transduction pathway, have been shown to be downregulated in mice lacking the ghrelin hormone. To corroborate this, we plan to compare expression of GPR120, CD36, and other FA signaling proteins such as Kv1.5 and TRPM5 in ghrelin-null and WT mice. Additionally, we hypothesize that taste cells primed with ghrelin in combination with fatty acids will show a remarkable change in cellular activity compared to their WT counterparts. Given that obesity is fueled, in part, by overconsumption in response to altered fat taste, our data suggest circulating ghrelin may play a role in these changes to taste cell responsiveness. Supported by NIH DC013194 and DC013318 (tag).

Characterization Of Drosophila Delta Glutathione Transferases Involved In Isothiocyanate Detoxification And Perception
Elodie Gonis, Stéphane Fraichard, Evelyne Chavanne, Jean-François Ferveur, Loïc Briand, Fabrice Neiers
CSGA, INRA, CNRS, Université de Bourgogne Franche Comté, DIJON, *, France

A variety of enzymes are found within Drosophila olfactory and taste hairs. These enzymes include cytochrome P450, esterases and glutathione transferases (GSTs). GSTs are ubiquitously found in animals. They catalyse the conjugation of glutathione to various compounds leading to their elimination. GSTs have been proposed to play a dual role in the protection of the chemosensory organs but more surprisingly in the chemosensory perception. Indeed when they modify odorant or tastant molecules, GST can also contribute to the sensory signal termination. GSTs include numerous families among which two insect specific families: GSTs Delta and Epsilon. The number of genes coding for both enzyme families has expanded during evolution in relation with the chemical diversity of environment. We propose to study the link between GSTs Delta and isothiocyanate molecules. Isothiocyanates are insecticidal compounds naturally present in plants and they are perceived by animals including Drosophila. Each GSTs of the Delta family was tested for its ability to conjugate six isothiocyanate molecules. The expression of the GST Delta was also quantified using PCR in the chemosensory organs before and after isothiocyanate exposure. The X-ray structure of a GST Delta involved in the chemoresistance toward isothiocyanate molecules was solved. We discuss the link of this GST family with it putative role in chemosensory perception.

Tmc6: A Novel Salt Taste Receptor In Mice
Takami Maekawa1, Koki Kamiya2, Tooru Takahashi1,3, Kentaro Kaji1,3, Yukio Tezuka1,3, Toshihisa Osaki2, Shoji Takeuchi2,4, Takashi Kondoh1
1Ajinomoto Co., Inc., Kawasaki, *, Japan, 2Kanagawa Institute of Industrial Science and Technology, Kawasaki, *, Japan, 3WDB Co., Ltd., Tokyo, *, Japan, 4Institute of Industrial Science, The University of Tokyo, Tokyo, *, Japan

Mechanism of amiloride-insensitive salt taste perception remains unclear. To find novel salt taste receptors, we investigated gene and protein expression in taste cells. Among them, it was found that transmembrane channel-like 6 (TMC6), a protein with unknown functions, was expressed in taste cells by single cell PCR and immunohistochemistry analysis. To perform functional analysis of TMC6, we generated Tmc6 knockout mice with C57BL/6J background and found that NaCl preference of the Tmc6 (-/-) mice, in the presence of amiloride, was largely decreased compared to the wild-type mice. Interestingly, the Tmc6 (-/-) mice showed normal preferences to sweet, sour, bitter and umami solutions. The results suggested that Tmc6 gene relates specifically to salt taste perception. By calcium imaging of CHO-K1 cells transfected withTmc6 gene, we found that the cells responded to NaCl stimulus. Finally, we embedded a purified TMC6 protein in an artificial lipid bilayer membrane and observed single ion channel-like currents under NaCl application. These results suggest that TMC6 is a novel ion channel that functions as a novel salt taste receptor in mouse taste cells.  

An Interruption Of Umami Peptide To The Salicin Binding To T2R16 Bitter Taste Receptor Can Be Enhanced By Imp
MeeRa Rhyu, Yiseul Kim, Minji Woo
Korea Food Research Institute, Jeollabuk-do, *, South Korea

Bitter-masking effect of umami peptides has long been found in human taste test. Yet we have only recently provided the evidence that umami peptides suppress bitterness via direct binding to bitter taste receptor in cells expressing T2R16. Similar bitter-masking effect through direct binding to bitter taste receptor was verified for other umami compounds including MSG, N-geranyl cyclopropylcarboxamide, and theanine. A distinct characteristic of umami taste is strong synergism by 5’ ribonucleotides, such as IMP or GMP. To test whether the synergism of umami taste applies to the bitter-masking, we investigated the interaction between IMP and MSG or Glu-Glu to the salicin-induced Ca2+ influx in cells expressing T2R16 using Ca2+-flux signaling assay. We maintained pH 7.4~7.25 of all assay systems with 100 mM HEPES (pH 7.4) to exclude acidic effect coming from samples. IMP itself has little effect on salicin-induced intracellular Ca2+ influx, whereas the efficacy of MSG suppressing salicin-induced Ca2+ influx can be enhanced by IMP in a dose-dependent manner. Also, the efficacy of Glu-Glu suppressing salicin-induced Ca2+ influx was effectively enhanced by pretreatment of IMP. These observations indicate that a distinct synergism of umami taste by 5’ ribonucleotides is crucial for the bitter-masking effect of umami compounds and that the synergism is to be involved in interacting with bitter taste receptor.

9:00 - 10:00 AMEstero Foyer
Coffee Break

10:00 - 12:00 PMCalusa FGH

Chair(s): Maria Veldhuizen


Chemical Senses: Intero- Or Exteroception? Introduction

Maria Veldhuizen
Yale University

Extero- and interoception both are relevant to maintaining homeostasis and adaptations to changes in the environment.  Exteroception concerns the perception of stimuli outside the body. Interoception is the sense of the internal state of the body. The chemical senses of taste and smell are considered part of the external senses, as they transduce chemical signals from the environment. The activation of their sensory pathways always precedes food intake and these senses play an important role as gatekeepers for homeostatis. As such they may be considered as intermediate between intero- and  exteroception. How does perception via the chemical senses resemble interoception and how are the functionality of the proximal exteroception via the chemical senses and interoception related?


Mapping Gustatory And Interoceptive Responses In The Primate Brain. Insights Into The Insular Cortex

Renee Hartig

A combination of functional and anatomical methods was used to help localize the representation of gustatory and interoceptive processes in the macaque cortex. Under anesthesia, neuroimaging (fMRI) and electrophysiology experiments were conducted during a series of functional stimulation paradigms, which included the application of different tastants (sour, sweet and salt) and distention of the lower gastrointestinal tract. The resulting BOLD activity in key subcortical (e.g. PAG, PbN, thalamus, amygdala) and cortical (e.g. insula, cingulate, SFG) structures was examined in an effort to delineate the sensory afferent relays and elucidate the connectivity between the primary cortical recipient of visceral and gustatory information – the insular cortex – and associated regions involved in the maintenance of homeostasis and the manifestation of emotional and cognitive percepts related to the elicited bodily sensations. Whole-brain fMRI analyses eventually developed into a more refined sampling of the insular cortex by electrophysiology, which identified neuronal population activities underlying such functional processes. 


Integration Of Gustatory And Interoceptive Processing In The Human Insula

Jason Avery
National Institute for Mental Health

The homeostatic regulation of feeding behavior requires an organism to integrate information from its internal environment, including peripheral signals about the body’s energy needs, with information from its external environment, such as the palatability of food sources. The insula, which serves as the brain’s primary viscero-sensory and gustatory cortex, is a likely region in which this integration might occur. Previous human neuroimaging studies, which have separately examined tasks of visceral interoception and taste perception, identified a region within the dorsal mid-insula that seemed to be involved in both of these functionally diverse tasks.

We performed two neuroimaging studies to further examine this possibility. Within the first study, a group of healthy volunteers underwent fMRI while performing a task involving interoceptive attention to visceral sensations and a gustatory mapping task, in which sweet and neutral tastants were delivered onto their tongues during scanning. We identified distinct as well as overlapping clusters of activation for both tasks within neighboring regions of the dorsal mid-insula.

In the second study, we examined these regions of functional overlap using an fMRI-Adaptation task design, in which tastant delivery events during scanning were preceded by either interoceptive or exteroceptive attention. We observed that, within the dorsal mid-insula, the hemodynamic response to sweet tastants which followed interoception was significantly smaller than the response to tastants which followed the exteroception control condition. The results of these two studies suggest that tasks of gustation and interoception not only co-activate the same region of the dorsal mid-insula, they involve a shared population of neurons. This sensory convergence within the dorsal mid-insula could serve as one mechanism by which visceral signals from the periphery modulate the activity of brain regions involved in feeding behavior.

The Impact Of Odor Perception On Interoceptive Awareness
Kathrin Kollndorfer
Medical University of Vienna

The perception of the internal physical state, also called interoception, is is importat for human beings. The representation of the internal state and its interpretation highly influences human behavior. Although interoception was often considered as separate from exteroceptive senses, previous research suggests that internal and external information will be integrated in the brain to create a complete picture of the current state and to react appropriately. Misinterpretations of the internal state is part of various mental disorders. However, also the lack of external information - such as olfactory dysfunction - may influence the perception of the internal state.


Cortical And Subcortical Representations Of Interoceptive Inputs From Microbial Populations In The Gut

Esposti Federico
San Raffaele University Hospital


Understanding the complex interplay between gastroenteric information (from food or bacteria) and brain functioning requires a deep analysis of the neuronal substrate where gut-derived information is processed in the brain. In this work we decided to undertake the analysis of the mouse brain responsivity pattern to intraluminal administration of molecules of bacterial origin, in order to understand which networks the brain employs to analyse microbiota-related information travelling along the gut-brain axis.


We mapped cortical and subcortical responses to intraluminal stimulation in C57BL/6 mice by functional ultrasoundimaging, performed through a cranial window exposing the whole brain in the medio-lateral direction, and spanning a length of ±2 mm around bregma in the rostrocaudal direction. The stimulation was performed by injecting LPS from E. coli, the short fatty acid Propionate, various fractions from the cultivation of Lactobacillus JB-1, water or glucose 10%. To distinguish responses related to the injection procedure (e.g. piercing of the gut wall) from the ones linked with the administration of bacterial or nutritional molecules, we separated the two events in time (10 seconds apart).


We found that the administration of bacterial molecules in the gut lumen evokes responses mainly from hypothalamic (homeostatic) and limbic regions, with an extensive activation of all the major nuclei of the amygdala. In this regard, bacteria-related inputs resemble much closely water-induced responses, which are known to activate extensive homeostatic control networks, involved in fluid balance and blood pressure management, than glucose-induced responses, which are mainly limited to interoceptive sensory areas, such as the Insular cortex. Moreover, bacterial molecules did also elicit pronounced activity in the hippocampus, whose physiological meaning will require further and deep investigations.

These results show for the first time that the mammalian brain can detect the presence of different bacteria in the gastrointestinal tract through interoceptive circuits, and can produce different responses depending on the nature of the bacterial input. Also, these results show for the first time how bacterial responses differ from food-related responses in the brain, expanding our knowledge about the functional diversity on central interoceptive networks in the brain. 

10:00 - 12:00 PMCalusa ABC

Chair(s): Benjamin Allen and Charlotte Mistretta

Benjamin Allen


Hedgehog Signalling In Taste Receptor Cells And Other Chemosensory Epithelia

Robert Margolskee
Monell Chemical Senses Center

Hedgehog (Hh) signalling is a principal regulator of cell proliferation and differentiation in many types of epithelial tissues, including gut, lung, taste papillae and taste buds. In adult mice, taste cells survive only a few days to a few weeks, necessitating their regeneration throughout life. In anterior tongue, sonic hedgehog (Shh), released by a subpopulation of basal taste cells and gustatory neurons that innervate taste buds, signals through the integral membrane receptor complex Patched and Smoothened to regulate zinc finger transcription factors Gli2 and Gli3, principal effectors of the Hh pathway in adults. In the absence of Shh signaling, Gli2 and Gli3 are C-terminally truncated to generate transcriptional repressors that are mostly sequestered in the cytoplasm. Shh signaling prevents the proteolysis of Gli2 and Gli3 and promotes their localization to the nucleus, where they regulate the expression of multiple target genes. Shh is known to regulate fungiform papillae development and patterning, but the downstream transcriptional effectors of hedgehog signalling in taste organ maintenance are largely unknown. Gli3 is a key transcriptional effector in the sonic hedgehog signalling pathway, but its distribution in the adult tongue and its role in taste bud maintenance was previously unknown. We used RNA sequencing of single taste cells and bioinformatics to determine that Gli3 is more highly expressed in type II taste cells and stem cells than in type III taste cells. Gli3 is selectively expressed in Tas1r3-expressing type II taste cells and Lgr5-expressing taste stem cells, but not in 5-HT-expressing type III taste cells or Glast-expressing type I taste cells. Behavioral tests showed that in comparison to wildtype Gli3 conditional knockout mice are more sensitive to sweet compounds, less sensitive to bitter and sour compounds, and similarly responsive to umami and salty compounds. Recording from the glossopharyngeal nerve showed that Gli3 conditional knockout mice are much more responsive to sweet and bitter compounds than are wildtype mice. Moreover, in vivo in Gli3 conditional knockout mice, significant increases were observed in the size of the taste buds and the number of taste cells in each taste bud, as well as in the number of taste receptor cells per taste bud. In an ex vivo taste organoid system we found that conditional loss of Gli3 from Lgr5+ stem cells led to increased numbers of Tas1r3+ cells and decreased numbers of Car4+ type III cells. Thus, in adult taste cells Gli3 functions as a negative regulator of differentiation and/or survival of taste stem cells and Tas1r3+ type II taste cells that influences taste receptor cell composition and function. In other organoid experiments we found that the Gli antagonist GANT61 arrested growth of taste organoids, especially in the early stages of culturing. In sum, broadly interrupting Gli mediators of Shh signaling prevents taste stem cells from proliferating in cultured taste organoids, while selective inhibition of Gli3 affects relative numbers of type II vs. III cells.

Acknowledgements: Supported by NIDCD/NIH grant R01DC014105 to RFM.



Lingual Epithelium, Hedgehog Signaling, And Taste Organ Homeostasis And Sensory Function

Archana Kumari, Charlotte Mistretta
University of Michigan

Lingual papilla organs include taste bud and non-gustatory cells in complex epithelia that interact with one another, and with stromal cells and nerves. An orchestrated signaling regulation among all of these cell types is essential to taste organ homeostasis and sensation, and the Hedgehog (Hh) pathway is a known regulator for papilla maintenance. The Sonic Hh ligand is in taste bud cells and Hh-responding, Gli1+ epithelial cells are perigemmal to the taste bud and in the papilla basal epithelium. Other Hh pathway components are in taste and non-taste epithelium. If signaling is inhibited with the cancer drug sonidegib, the Hh-responding, Gli1+ epithelial cells are eliminated, with loss of taste buds and associated Shh; this is accompanied by a pattern of reduced proliferation in basal cells of the apical fungiform papilla and a differentiation defect in the papilla epithelial apex. Nerves remain in the taste papilla core, extending to and into the epithelium. Notably, responses from the taste nerves to chemical stimulation of the tongue are eliminated; however, responses to tongue tactile and cold stimuli are retained.  Thus, with Hh signaling deregulation the taste buds and taste responses are compromised, whereas complex epithelial nerve endings and somatosensory responses are intact. If Hh signaling inhibition is terminated by drug withdrawal, then papilla morphology and taste bud numbers are partially restored. Nerve responses to lingual chemical stimulation return, accompanied by renewed Hh signaling in the taste organ epithelium. Hh signaling cells are reconstituted in papillae with a taste bud and Shh, but not in papillae that remain dysmorphic and lack taste buds. Hh signaling in taste organ epithelium is cell specific, and is necessary for and directly associated with sensory function.
Supported by NIDCD NIH Grant DC014428.


Investigating The Role Of Gli Proteins During Regeneration Of Olfactory Epithelia

Anna Shirazyan
University of Michigan

The olfactory epithelium (OE) is comprised of several cell types, including olfactory sensory neurons (OSNs), sustentacular cells (SUS), and microvillar cells (MVC), which can be replenished by two presumed stem cell populations:  globose basal cells (GBCs), and horizontal basal cells (HBCs). While HBCs and GBCs both contribute to OE regeneration, the signaling pathways that control this process are not well understood. Recent work indicates that HBCs contain primary cilia, cellular organelles that coordinate signals from multiple pathways. Notably, primary cilia are essential for proper vertebrate Hedgehog (HH) signal transduction, making the HH pathway a candidate in the control of HBC function. Further, HH signaling is important in another chemosensory organ, the tongue, where HH pathway blockade results in abnormal taste bud maintenance. GLI proteins are the transcriptional effectors of the HH pathway – GLI1 functions exclusively as a transcriptional activator and is a target of HH signaling; GLI2 is the major transcriptional activator of the HH pathway; conversely, GLI3 acts largely as a transcriptional repressor. Preliminary data suggest that Gli2 and Gli3 are expressed in HBCs, and that Gli2 expression expands in the OE following severe injury. To assess possible GLI function in HBCs, we utilized doxycycline-inducible expression of a constitutively active form of GLI2 to stimulate the HH pathway specifically in HBCs (K5-rtTA; tetO-GLI2ΔN). Our data indicate that HBC-specific activation of GLI2 causes hyperproliferation of HBCs that are then unable to differentiate and reconstitute the OE after methimazole-induced injury. This suggests a novel contribution of GLI proteins to HBC-mediated OE regeneration. Future studies will investigate the roles of endogenous GLIs in HBC function.


Role Of Hedgehog In The Maintenance Of Resident Stem Cell Niche In The Adult Lung

Tien Peng
University of California, San Francisco, CA, United States


Benjamin Allen

12:00 - 1:00 PMLunch On Own
Lunch On Own

1:00 - 3:00 PMCalusa FGH

Chair(s): Valentina Parma and Jonas Olofsson

Valentina Parma


Mechanisms Of Odor Identification Examined With Neuro-Cognitive Methods

Jonas Olofsson
Stockholm University

The ability to recognize a smell, odor identification, is highly dependent on multisensory context and expectation, for example, hearing the name of the odor source. In humans, impairment on olfactory identification tasks is a sensitive predictor of age-related cognitive decline, Alzheimers’ type dementia, and mortality. How multisensory associations are formed in the olfactory system is, however, poorly understood. I will review results from an experiment where we trained rats to make odor-tone associations in a task that is similar to odor identification assessments. We conducted physiological analyses of sensory-evoked local field potential activity in primary auditory cortex and anterior piriform cortex. Results show enhanced beta-band activity in both cortical areas, as well as cross-regional functional connectivity, suggesting a multisensory integration mechanism underlying odor identification. These results are discussed in the context of  the processes known to underlie human odor identification.


Is Odor Language Embodied?

Laura Speed
The University of York

Embodied approaches to language propose that when comprehending language, the sensorimotor systems are activated. But, olfaction is thought to be weakly connected to language. Is odour language embodied like language related to other sensorimotor domains? We present behavioural evidence suggesting that odour-related words (e.g., cinnamon) do not activate low-level olfactory representations. Instead, one route to processing odour language could be to ground it in other perceptual modalities, such as colour.


Why Smell Words Do Not Come Easily? Pathways To Olfactory Lexicon

Francesca Franzon
International School for Advanced Studies (SISSA)

Languages seem to lack words that are uniquely dedicated to olfaction, differently from other senses. Olfactory information is mostly encoded in words denoting an odor source, linked to a multi-sensory representation.

Data from a large rating study, collected primarily on Italian native speakers, will allow to characterize different degrees of information and abstractness in source-based olfactory words. We will model the informative properties of words related to the olfactory domain, by comparing them to other sensory/semantic domains and discuss the communicative efficiency of olfactory encoding.


How Language And Cognition Shape Olfaction

Theresa White
Le Moyne College

Language is a key feature of cognition that allows thoughts to be externally expressed.  Linguistic relativism asks whether the structure of language also modifies thought.  So, do people who speak languages that employ grammatical gender think of some objects as more masculine or feminine than people who speak languages that do not have that linguistic convention?  Odorants are unique stimuli for examining this question, as they have been described as having gender as a central dimension.  In addition, odorants are paradoxically both difficult to label and highly influenced by labels.  In the present study, French-Canadian bilinguals and native English speakers described a set of odorants that varied systematically in grammatical gender and in anthropomorphized semantic gender (determined via pilot with English speakers).  The odorants were presented to participants in bottles that were labeled in English, and participants were unaware as to the purpose of the study.  Analysis of the implicit femininity contained in French participants’ descriptions of the odorants that were mismatched for grammatical and semantic gender seemed to show a tendency for French speakers to produce language consistent with grammatical gender; however, analyses of the English speakers indicated a similar effect.  These results indicate that a strong influence of semantic gender pervaded both speaker groups, and suggest that in a bilingual culture, French speakers may have influenced the anthropomorphism associated with odorants in a way that is consistent with language.  

1:00 - 3:00 PMCalusa ABC

Chair(s): Hubert Amrein

Hubert Amrein
Texa A

The Fat Tastes Different: The Perception And Discrimination Of Fatty Acids In Drosophila
Pavel Masek1, Yuanyuan Li1, Alex Keen2, John Tauber2, Elizabeth Brown2, Jake Gordon1
1Binghamton University, Binghamton, NY, United States, 2FAU, Jupiter, FL, United States

Fat represents the most calorically potent food source per unit of mass. Previously, we showed that a broad population of sugar-sensing taste neurons expressing Gustatory Receptor 64f (Gr64f), is required for reflexive feeding responses to sugars but also to free fatty acids (FAs), one of the building blocks of fat. A functional Phospholipase C pathway in these neurons is specifically needed only for FAs perception. The detection of different chemicals through the same neurons but through different biochemical pathways was described in other insects but the implication of this separation remains unclear. We now describe specific populations of taste neurons mediating FA taste that are identified by expression of Ionotropic Receptor 56d (IR56d). IR56d together with IR76b and IR25a are necessary for perception of FAs. Functional imaging reveals that these neurons response to short- and medium-chain FAs and are necessary and sufficient to drive the feeding responses. Behaviorally, we show that flies display different response to FAs and sugars relative to their intensity. They show increasing preference to sugars with increasing concentration but prefer FAs at low concentrations and avoid them at high, likely due to involvement of bitter sensing neurons. Flies can also discriminate between sugars and FAs using an aversive taste memory assay. These results support the notion that the taste of FAs is a unique taste modality. We further test discrimination between multiple FAs from various categories including medium and long carbon chain; saturated, mono and poly unsaturated. Here we describe different modes of tastants discrimination that allows us to categorize appetitive taste stimuli into functional groups and will help us to further understand the diversity in the taste modalities.


The Taste Of Rna In Insects

Ji-Eun Ahn1, Dushyant Mishra2, Christopher Jagge1, Chika Miyamoto1, Hubert Amrein1
1Texas A&M University Health Science Center, College Station, TX, United States, 2University of Connecticut, Storrs, CT, United States

Most animals employ various types of taste receptors to identify essential macronutrients, such as sugars, amino acids and fats, as well as noxious compounds generally perceived as bitter. Drosophila has emerged as the main insect model system for functional analyses of taste receptors and the neural circuitry of taste behavior, and receptors for sugars, bitter chemicals, acids, fatty acids and proteins have been identified. Here, we report that Drosophila and other insect larvae exhibit appetitive taste behavior for RNA and ribonucleosides. We show that RNA and ribonucleosides are essential nutrients for Drosophila to support accelerated growth and survival during the larval stages. Moreover, we find that the Gustatory receptor 28 (Gr28) gene subfamily encode receptors for RNA and ribonucleosides through the ribose moiety in these chemicals. CAMPARI based Ca2+ imaging established that terminal organ taste neurons respond to ribose, inosine, uridine and tRNA in Gr28-dependent manner. Finally, heterologous expressions of single Gr28 genes in fructose-sensing neurons which do not express any of the Gr28 genes, conveys responses to ribose and RNA and can rescue attraction to these chemicals in homozygous mutant Gr28 larvae. To examine whether RNA taste is a general insect modality, we examined larval preference behavior of the blowflies L. cuprina and C. rufifacies and the mosquito A. aegypti. Larvae of all three species show strong attraction to ribose and RNA. Finally, expression of A. aegypti Gr9a, a Gr28 homolog, in Drosophila taste neurons rescues appetitive behavioral responses to ribose and RNA of Gr28 mutant larvae. Our studies have uncovered a new nutrient for insect larvae, RNA, and identified Gr28 proteins as the molecular receptors.


Reshaping Of Sweet Taste Sensation And Feeding By A High Sugar Diet

Monica Dus, Christina May, Anoumid Vaziri
University of Michigan, Ann Arbor, MI, United States

Taste sensation can change with diet. For example, high dietary sodium alters the intensity for salt perception and promotes higher sodium intake. Similarly, exposure to savory or bitter foods changes taste preference in humans, rodents , and invertebrates. Over the past decades our diets have become sweeter because of the use of sugar as a food additive: today over 75% of foods sold at grocery stores contain added sugar. During the same time, daily calorie intake increased by 20%. Whether high dietary sweetness alters sweet taste sensation however, is unknown. Here we asked whether high dietary sugar decreases sweet taste function to promote overconsumption and obesity. To tackle this question, we exploited the relative simplicity of the Drosophila taste system, where the sweet-sensing cells are neurons that project directly to the brain. We show that fruit flies fed a high sugar diet show a dulled sense of sweet taste because of lower responses of the sweet taste neurons to sugar and that this deficit is caused by high dietary sugars, not obesity. By monitoring feeding behavior at high resolution and using opto- and neurogenetics manipulations of sweet taste cell activity, we show the dulling of sweet taste leads to overfeeding and obesity. Preventing a decrease in sweet taste sensation rescues feeding and fat accumulation in animals exposed to the high sugar diet. Our results implicate deficits in sweet taste as drivers of obesity and begin to map the neural underpinnings through which exposure to high dietary sugar reshapes taste function and behavior.


Circuit Dissection Of Taste Processing In Drosophila

Kristin Scott1, Gabriella Sterne1,2, Barry Dickson2
1University of California Berkeley, Berkeley, CA, United States, 2Janelia Research Campus, Ashburn, VA, United States

Appropriate feeding decisions are essential to individual and species survival. In Drosophila, like mammals, neural circuits process information about taste and internal nutritive state to generate feeding decisions. Although gustatory sensory neurons and feeding motor neurons coexist in the same brain area, the subesophageal zone (SEZ), the circuitry that transforms taste information into a feeding motor sequence is unknown. To identify neural components of the feeding circuit, we designed a novel split-Gal4 collection which genetically labels individual SEZ interneurons. An optogenetic activation screen of this collection has uncovered an unprecedented number of novel SEZ neuron types that trigger aspects of the feeding motor program. However, only a handful of these newly-identified interneurons are required for feeding in hungry flies. Using pair-wise functional connectivity, GFP Reconstitution Across Synaptic Partners (GRASP), and neuron tracing in an electron microscopy volume, we are beginning to assemble a wiring diagram of these core feeding circuit interneurons. The completion of these experiments will produce the first-ever functional wiring diagram of Drosophila gustatory circuitry and will provide insight into the types of computations neural circuits perform to generate and carry out feeding decisions.

3:00 - 3:30 PMCalusa Foyer
Coffee Break

3:30 - 5:00 PMGreat Egret

Turnover and Renewal of Cells in Taste Buds: from Lloyd M. Beidler's Classic Paper of 1965 to Taste Cell Dynamics Five Decades Later

Brief Introduction To Achems Journal Clubs (From The History Committee)
Charlotte Mistretta
University of Michigan MI

Informal Introduction To The Beidler Laboratory And Principal Scientific Contributions From Lm Beidler
Robert Bradley
University of Michigan MI

The Classic Paper: Beidler Lm And Rl Smallman, Renewal Of Cells Within Taste Buds, Journal Of Cell Biology 27:263-272, 1965
Zachary Whiddon
Student in Anatomical Sciences and Neurobiology, with Robin Krimm, University of Louisville KY

To The Present: Commentary And Comments: New Data On Taste Cell Dynamics
Linda Barlow
University of Colorado CO

Reminiscences And Comments
The Beidler Laboratory: Comments from the Audience Hosts: Steven St. John, Robert Bradley

7:30 - 9:00 PMCalusa ABC
Award Lectures

Barry Jacobs Memorial Award: How The Properties Of Stimuli And Receptors Shape Olfactory Perception
Andreas Keller
The Rockefeller University

We perceive a smell when odorant molecules bind to the odorant receptors on sensory neurons in our nose. The perceptual qualities of the perceived smell largely depend on the receptor-odorant-interaction, which in turn depends on the chemical and physical properties of odorants and receptors. In the century-old tradition of psychophysics, we have investigated how the smell of a stimulus depends on its physical properties. Thanks to the large genetic variability in the human olfactory receptor repertoire, we also had an opportunity to determine how the perception of our olfactory environment depends on the properties of the odorant receptor repertoire. This two-pronged approach presents a first step in predicting how a given olfactory stimulus will be perceived by a given olfactory system.

Ajinomoto Award For Young Investigators: Solitary Chemosensory Cells Function As A Double-Edged Sword: Protective Sentinels Against Pathogens But Also Initiators Of Inflammation And Disease.
Marco Tizzano
Monell Chemical Senses Center

For a hundred years, researchers have known there is a population of epithelial cells with a tear/blob shape and a top brush of microvilli, named tuft, brush or solitary chemosensory cells (SCCs) depending on the mucosa that harbors them. What has been discovered in the last two-three decades is that these SCC-like cells display chemosensory capabilities and they harbor the same chemical-sensing taste receptors/downstream signaling pathway as do the tongue taste buds. SCCs are stationed in the lining mucosa of many body structures and organs including the nasal passages, intestines, lungs, pancreas, gallbladder, urethra, and more. A wave of recent research has revealed that SCCs serve as sentinels along the body's invasion routes, sensing pathogens and chemicals that are either inhaled or that attempt to infiltrate in other ways. Although not part of the immune or nervous system, SCCs interact with these systems to help coordinate protective responses against the xenobiotic invasion. But SCCs can also betray us; they are implicated in airway inflammatory conditions such as asthma and rhino-sinusitis or in other diseases such as cancer, flu and allergies. Research in my lab attempts to shed some of the mysteries of SCCs: (1) what pathogen molecules and allergens SCCs recognize, (2) which receptors and downstream mechanisms they deploy to sense pathogens, (3) what is the interaction of SCCs and the innate immune system, and (4) how do SCCs contribute to certain respiratory and oral diseases, and (5) how can SCCs be harnessed to become a major target of medical treatments. Our work is now hinting that SCCs in the respiratory system drive conditions such as allergies, asthma, and sinus inflammation. Our data show that whereas acute exposure to bacterial quorum sensing molecules stimulates the immune system upon activation of the SCCs, repeated long-term activation of the SCC pathway leads to chronic airway inflammation. Moreover, in the oral cavity, SCCs interact with the gingival microbiota and have a leading role in periodontitis, perhaps by releasing the same immune-stimulating molecules that trigger defenses against pathogens. In summary, stimulating SCCs can reduce bacterial invasions but, in contrast, blocking or stimulating with benign triggers these cells can help ease asthma, allergy symptoms, and periodontitis. Our research provides foundational basic science and explores how to translate this into novel approaches to promote health and treat mucosal inflammatory conditions.

Max Mozell Award: Studying Oral Chemoreception As A Multisensory Cutaneous System
Barry G. Green
The John B. Pierce Laboratory and Department of Surgery, Yale School of Medicine

Taste and chemesthesis provide critical chemosensory information about the safety and palatability of the things we ingest. Complicating this task is the dynamic mechanical and thermal environment of the mouth and the fact that many of the chemoreceptors serving taste and chemesthesis are also sensitive to temperature and/or touch. These factors together with large individual differences in the response to multisensory stimuli pose significant challenges to measuring and understanding oral chemical sensitivity in humans. This talk will describe approaches to studying this specialized cutaneous system that have been driven by chance discoveries and methodological necessity, and whose further refinement and use will be increasingly important for guiding the translation of rapid advances in neurobiology to human chemoreception.  

9:00 - 12:00 AMMangroves & Belvedere Room
Closing Dance Party