# Distinct mechanisms for memory storage and retrieval in hippocampal engram cells

> **NIH NIH R21** · UNIVERSITY OF CALIFORNIA AT DAVIS · 2021 · $423,823

## Abstract

Abstract
Neurobiological mechanisms underlying learning and memory have been extensively studied in animals. However, very
little is known about the cellular processes that support retrieval. This may be the case because retrieval is often
assumed to be a direct function of memory strength. The more learning that took place, the easier retrieval should be.
However, research on human memory has demonstrated that storage strength and retrieval strength are dissociable
processes. The former is long-lasting and influenced by the amount of training while the latter fluctuates and depends
on temporal factors like how long ago the memory was encoded and retrieved. These unique properties suggest that
storage strength and retrieval strength are regulated by distinct cellular mechanisms. Consistent with this idea,
norepinephrine (NE) release is required for memory retrieval in the hippocampus but is not necessary for learning.
Conversely, dopamine (DA) release is essential for learning but is not required for memory retrieval. Given that much is
already known about DA and the role it plays in learning, the current application will characterize the relationship
between NE release, intrinsic excitability and memory retrieval. In doing so, we will test the hypotheses that: 1) Phasic
release of NE during testing enhances memory retrieval and prevents forgetting 2) Phasic release of NE increases the
intrinsic excitability of engram cells and facilitates their reactivation during testing.

## Key facts

- **NIH application ID:** 10235095
- **Project number:** 1R21NS122356-01
- **Recipient organization:** UNIVERSITY OF CALIFORNIA AT DAVIS
- **Principal Investigator:** Brian J Wiltgen
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $423,823
- **Award type:** 1
- **Project period:** 2021-04-01 → 2022-09-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10235095

## Citation

> US National Institutes of Health, RePORTER application 10235095, Distinct mechanisms for memory storage and retrieval in hippocampal engram cells (1R21NS122356-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10235095. Licensed CC0.

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