Presentation Details
| Bilateral integration of odor information in the mouse Venkatesh N Murthy1, 2, Leannah Schmitt1, 2, Siddharth Jayakumar1, 2, Julien Grimaud3. 1Center for Brain Science, Harvard University, Cambridge, MA, USA.2Dept of Molecular & Cellular Biology, Harvard University, Cambridge, MA, USA.3SupBiotech, L’école des ingénieurs en biotechnologies, Paris, France |
Abstract
In the mammalian olfactory system, information from each nostril is thought to be mapped in a distributed and fragmented manner in higher brain regions, such that the same odor environment may be represented independently in the two sides. How can an animal create a consistent and unified internal representation from these differing pieces of evidence? The earliest brain region with interhemispheric projections is the anterior olfactory nucleus (AON), making it an excellent candidate for bilateral integration of odor information. We have found that the responses to odors sensed through the two different nostrils are highly correlated in each side of the brain. Such aligned representations mean that a population of cortical neurons will have very similar responses whether the animal smells the odor through one nostril or the other. With a simple mathematical model, we showed that random interhemispheric connectivity leads to uncorrelated representations, hence the mapping must be structured in some way. Indeed, matched odor representation can readily arise from conventional correlation-based, Hebbian synaptic plasticity of initially unstructured connections. Using viral tracing of specific subtypes of neurons within the AON, we have found that interhemispheric projections arise exclusively from glutamatergic neurons, but their axons target both glutamatergic and GABAergic neurons in the contralateral side. Optogenetics-assisted synaptic physiology revealed that contralaterally-projecting AON axons readily evoke monosynaptic excitation followed by polysynaptic inhibition. Collectively, our experiments point to structured integration of information in the two hemispheres in early olfactory cortical areas, setting the stage for future investigations into the origin of this structure and its function.
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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.