Rapid odor processing by layer 2 subcircuits in lateral entorhinal cortex

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Abstract

Olfactory information is encoded in lateral entorhinal cortex (LEC) by two classes of layer 2 (L2) principal neurons: fan and pyramidal cells. However, the functional properties of L2 cells and how they contribute to odor coding are unclear. Here, we show in awake mice that L2 cells respond to odors early during single sniffs and that LEC is essential for rapid discrimination of both odor identity and intensity. Population analyses of L2 ensembles reveals that rate coding distinguishes odor identity, but firing rates are only weakly concentration-dependent and changes in spike timing can represent odor intensity. L2 principal cells differ in afferent olfactory input and connectivity with inhibitory circuits and the relative timing of pyramidal and fan cell spikes provides a temporal code for odor intensity. Downstream, intensity is encoded purely by spike timing in hippocampal CA1. Together, these results reveal the unique processing of odor information by LEC subcircuits and highlight the importance of temporal coding in higher olfactory areas.

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Source data is provided for each figure containing the numerical data used to generate the figures.

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Sebastian H Bitzenhofer

Department of Neurosciences, University of California, San Diego, La Jolla, United States

For correspondence
seb.bitzenhofer@gmail.com

Competing interests
The authors declare that no competing interests exist.
Elena A Westeinde

Department of Neurosciences, University of California, San Diego, La Jolla, United States

Competing interests
The authors declare that no competing interests exist.
Han-Xiong Bear Zhang

Department of Neurosciences, University of California, San Diego, La Jolla, United States

Competing interests
The authors declare that no competing interests exist.
Jeffry S Isaacson

Department of Neurosciences, University of California, San Diego, La Jolla, United States

For correspondence
jisaacson@ucsd.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0001-9052-5211

Funding

National Institute on Deafness and Other Communication Disorders (R01DC04682)

Jeffry S Isaacson

National Institute on Deafness and Other Communication Disorders (R01DC015239)

Jeffry S Isaacson

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) protocols (#S977M)) of the UCSD. All surgery was performed under halothane anesthesia, and every effort was made to minimize suffering.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.