# Hippocampal Influences on Auditory Cortical Circuits as a Function of Brain State and Learning

> **NIH NIH R01** · CALIFORNIA INSTITUTE OF TECHNOLOGY · 2021 · $412,500

## Abstract

Project Summary
 The hippocampus plays a critical role in the formation of episodic memories. The current predominant
hypothesis is that memories are gradually established across distributed cortical networks under the influence
of hippocampal activity. However, our understanding of the nature and extent of hippocampal influences on
cortical circuits remains incomplete. Part of the challenge has been that any subthreshold modulation of
cortical neurons is inaccessible to extracellular recordings, which have been the main tool for studying of
cortico-hippocampal interactions. We propose to combine whole-cell recordings in auditory cortex (AC) with
optogenetic control of the projections to this area from the hippocampal complex (HC), in order to quantify the
influence of the HC-AC projections on the membrane potential dynamics of individual cortical neurons as a
function of brain state and learning. We aim to use this approach to identify cortical neurons that receive direct
hippocampal input, and characterize their properties and the plasticity of the corresponding synapses in vivo.
Finally, we aim to use optogenetic perturbations of the HC-AC projections during learning events and
hippocampal ripples to establish the functional role of these projections in memory formation, and to study the
timing of their participation in the consolidation process. Quantifying the subthreshold modulation of cortical
neurons by hippocampal inputs can provide sensitive measures of the functional coupling between these areas
and bring us closer to a mechanistic understanding of their interactions and their role in memory formation.

## Key facts

- **NIH application ID:** 10085677
- **Project number:** 5R01MH113016-05
- **Recipient organization:** CALIFORNIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** ATHANASSIOS SIAPAS
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $412,500
- **Award type:** 5
- **Project period:** 2017-03-01 → 2022-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10085677

## Citation

> US National Institutes of Health, RePORTER application 10085677, Hippocampal Influences on Auditory Cortical Circuits as a Function of Brain State and Learning (5R01MH113016-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10085677. Licensed CC0.

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