Presentation Details
| Synaptic plasticity and ensemble representation in Piriform Cortex Anne-Marie M.Oswald. Neurobiology, Neuroscience Institute, University of Chicago, Chicago, IL, USA |
Abstract
Olfactory stimuli are typically mixtures of different odor molecules. Odor mixtures can be identified elementally, whereby individual components drive perception, or configurally as an odor object. The odor components are parsed by the olfactory bulb, which relays this information to the anterior piriform cortex (APC) where component information may be recombined. Within the APC, pyramidal neurons (PNs) receive afferent odor information on their distal dendrites and recurrent excitation proximally. Coactivation of afferent and recurrent pathways results in associative plasticity at recurrent synapses. This plasticity is thought to underlie to the formation of long-term ensemble representations of olfactory stimuli. To assess synaptic strength within neural ensembles following odor learning, we used transgenic FosERT mice that allow targeted recombination in active populations (TRAP). We trained FosERT mice to discriminate two overlapping mixtures in a digging task. Once the mice reached criterion, we used TRAP to express tdTomato and ChR2 in ensembles that were specifically active during presentation of the rewarded or unrewarded odor mixture. We then reactivated the ensemble PNs in vitro to compare synaptic strength between PNs within ensemble (tdtom+) versus PNs outside the ensemble (tdtom-). We found that synapses are specifically strengthened within ensembles that respond to the rewarded odor. Surprisingly we found that synapses remain weak within ensembles responsive to the unrewarded odor. Further experiments revealed that mice use component (elemental) information to solve the task, rather than the mixtures as a whole (configural). Our findings suggest this task-specific information is represented by changes in synaptic strength between PNs within ensembles in APC.
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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.