# Integration of Sensory and Temporal Information in CA3

> **NIH NIH F30** · UNIVERSITY OF CALIFORNIA LOS ANGELES · 2023 · $30,188

## Abstract

ABSTRACT
Memories are temporally organized. When we recall an event, we also recall the relative timing it was
experienced. How does the brain compute and store this temporal representation of memory? The
hippocampus is important to the temporal organization of memories. Hippocampal CA1 or CA3 lesions cause
impaired coding of sequential events separated by time. The hippocampus bridges stimuli-free gaps between
sequential events through neural ensembles that fire sequentially during the delay. These “time cells” fire
sequentially encoding successive moments during the delay. Recent work in our laboratory and other groups
have confirmed and furthered these findings. They have found that the CA1 region of the hippocampus
contains neurons that display stimulus-specific sequential firing patterns during the delay period of a working
memory task. CA1 largely lacks recurrent connectivity, so it is unlikely that it generates these sequential firing
patterns on its own. CA3 is an upstream region with direct connections through the Schaffer collaterals to CA1.
CA3 has extensive recurrent connections and is a likely candidate that generates these stimulus-specific
sequential firing patterns. The recurrent connections in CA3 are well-suited for storing and working with
temporary information because they allow for rapid associations. CA3 also receives input from the lateral
entorhinal cortex, which processes nonspatial sensory information and receives direct connects from the
olfactory bulb. To date, it is unknown where and how sensory and temporal information is integrated. Given the
unique attributes of CA3, we propose that CA3 is where sensory and temporal information is integrated and
then this code is passed onto CA1. To test this hypothesis, we will use cutting-edge chronic in vivo two-photon
calcium imaging to monitor CA3 neuronal populations during a working memory task. Additionally, we will use
simultaneous in vivo two-photon imaging and optogenetics to modulate targeted sub-populations within CA3
that are active during stimulus presentation or during the delay period of a working memory task. This will allow
us to examine the causal relationships between sensory and temporal information. These experiments will lay
the groundwork for understanding how elements of a memory are unified and coded within CA3.

## Key facts

- **NIH application ID:** 10593095
- **Project number:** 5F30MH125638-03
- **Recipient organization:** UNIVERSITY OF CALIFORNIA LOS ANGELES
- **Principal Investigator:** Stephanie Cheung
- **Activity code:** F30 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $30,188
- **Award type:** 5
- **Project period:** 2021-04-16 → 2023-12-15

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10593095

## Citation

> US National Institutes of Health, RePORTER application 10593095, Integration of Sensory and Temporal Information in CA3 (5F30MH125638-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10593095. Licensed CC0.

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