Presentation Details
| Integration of glomerular activity assembles the components of odor scenes Kristyn Lizbinski, Gizem Sancer, Kay Ellison, Helen Mao, Madeline Albanese, James Jeanne. Yale University, New Haven, CT, USA |
Abstract
Natural odor scenes activate many odorant receptor types and, accordingly, many glomeruli in the brain. Projections from glomeruli activated by different components of an odor scene tend to converge onto the same higher-order neurons. For example, the scene of fermenting fruit contains volatile acids and esters which activate different glomeruli in Drosophila, and the corresponding projection neurons (PNs) target many of the same third-order lateral horn neurons (LHNs). However, we do not understand how, or even if, this architecture produces representations of behaviorally salient odor scenes. Here, we combine behavior, in vivo calcium imaging, electrophysiology, and connectome analysis in Drosophila to determine how LHNs process their PN inputs. We measure the responses of nearly all 51 olfactory glomeruli and 20 distinct LHN types to apple cider vinegar and 11 food-related monomolecular odorants. While apple cider vinegar is the most behaviorally attractive odor, it does not evoke the strongest response in any PN. However, it does drive the strongest response in two LHN types. Relative odor responses in these LHNs are preserved under pharmacological blockade of local inhibition, pointing to feedforward mechanisms of enhancement. Causal manipulation of PN activity during LHN recording reveals that glomeruli encoding acids and glomeruli encoding esters integrate linearly to assemble the odor scene of vinegar. A linear model also predicts much of the odor tuning across all sampled LHNs, identifying a uniform computation throughout the lateral horn. Our findings imply that LHNs encode evidence for odor scenes in a graded fashion, responding modestly to individual components and strongly to all components. The lack of nonlinearity preserves information, which likely benefits behavioral decisions.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.