# Effect of hippocampal feedback projections on the function of the early olfactory system

> **NIH NIH R01** · UNIVERSITY OF ROCHESTER · 2024 · $549,288

## Abstract

Project Summary/Abstract
The neural circuits associated with encoding odors in patterns of activity throughout the brain are critical not
only for chemosensory perception, but are intimately linked to emotion, learning and memory in humans and
mice, the major animal model for studying disorders that impact chemosensory function. We propose to study
the circuit between the ventral CA1 (vCA1) region of the hippocampus and the main olfactory bulb (MOB) to
between understand how cognitive aspects of behavior, such as a sense of environment, or anxiety can
influence the encoding of chemical signals. Improved understanding of these circuits could provide critical
insight into the link between chemosensory function and neurological, neurodegenerative, and
neuropsychiatric disorders.
Mitral and tufted cells (M/T) are the principal neurons of the main olfactory bulb (MOB) in rodents, and relay
chemosensory information they receive to a number of cortical regions including the anterior olfactory nucleus
(AON) and the piriform cortex. Rather than active as passive relays of this information, mitral and tufted cell
activity is reshaped in part by local inhibitory interneurons and by extensive feedback projections from a
number of areas including olfactory cortex and the hippocampus. We have recently begun exploring the
structure of one of these feedback circuits, projections from the pyramidal cells of the ventral CA1 (vCA1)
region of the hippocampus. Although these connections were identified nearly a ½ century ago, little is known
about their function. In this proposal, we will investigate the overall hypothesis that vCA1 projections relay
behaviorally relevant cognitive information (representing where the animal is, the anxiety associated with that
location in the environment, etc.) to the MOB.
Using a combination of electrophysiology and behavioral measures, we will ask three critical questions about
the vCA1->MOB circuit. (1) What behavioral information do the vCA1 neurons that project to the bulb encode?
(2) What are the synaptic networks that link vCA1 to the M/T cells in the bulb? (3) What if any of these
behavioral features are represented in the bulb and how does this affect chemosensory processing?
Combining these studies will provide critical insight into the circuits that allow behavior to shape chemosensory
perception.

## Key facts

- **NIH application ID:** 10878291
- **Project number:** 1R01DC021141-01A1
- **Recipient organization:** UNIVERSITY OF ROCHESTER
- **Principal Investigator:** Krishnan Padmanabhan
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $549,288
- **Award type:** 1
- **Project period:** 2024-08-10 → 2029-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10878291

## Citation

> US National Institutes of Health, RePORTER application 10878291, Effect of hippocampal feedback projections on the function of the early olfactory system (1R01DC021141-01A1). Retrieved via AI Analytics 2026-06-12 from https://api.ai-analytics.org/grant/nih/10878291. Licensed CC0.

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