# Layer 1 Circuitry in Mouse Auditory Cortex

> **NIH NIH R21** · MASSACHUSETTS EYE AND EAR INFIRMARY · 2020 · $170,000

## Abstract

Project Summary
The circuitry and function of sensory cortices, including auditory cortex, are sensitive to changes in experience
and sensory environment. Neurons in layer 1 (L1) of cortex have a privileged position in controlling the activity
and plasticity of cortex induced by salient experiences. L1 contains a small number but diverse class of
inhibitory neurons that nearly all express the ionotropic serotonin 5-HT3A receptor. These neurons are known to
increase cortical activity by inhibiting other inhibitory GABAergic interneurons. Nevertheless, the mechanisms
by which L1 neurons are activated and control cortical state are not fully understood. We unexpectedly found
that, in primary auditory cortex (A1), L1 neurons receive a direct and tonotopically-organized input from
auditory thalamus. Furthermore, we made the surprising discovery that L1 neurons send inhibitory projections
back to thalamus. Here we propose to use anatomical, electrophysiological, and viral approaches to elucidate
the pre and post-synaptic partners of 5-HT3A-expressing neurons in L1 of A1, focusing on the possibility of a
closed loop from thalamic relay neurons to L1 neurons and back. Our findings suggest that classical models of
cortico-thalamic interactions are incomplete and indicate that L1 receives tuned sensory input and contains
projection neurons. These studies will lay the foundation of a future RO1 examining the functional effects of
this novel inhibitory cortico-thalamic projection on the activity and plasticity of A1 circuits.

## Key facts

- **NIH application ID:** 9869701
- **Project number:** 5R21DC016991-03
- **Recipient organization:** MASSACHUSETTS EYE AND EAR INFIRMARY
- **Principal Investigator:** ANNE E TAKESIAN
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $170,000
- **Award type:** 5
- **Project period:** 2018-03-01 → 2022-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9869701

## Citation

> US National Institutes of Health, RePORTER application 9869701, Layer 1 Circuitry in Mouse Auditory Cortex (5R21DC016991-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9869701. Licensed CC0.

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