# Generation of a dual transgenic/viral system to characterize multiple engrams in a single mouse

> **NIH NIH F99** · COLUMBIA UNIVERSITY HEALTH SCIENCES · 2022 · $47,752

## Abstract

PROJECT SUMMARY / ABSTRACT
Memories are thought to be stored through lasting physical and chemical changes in the brain. The biological
substrate of a memory is known as an engram or memory trace. An engram is the neural ensemble activated
during learning and whose reactivation by the original stimulus results in memory retrieval. Modern
technological advances have allowed scientists to visualize and manipulate engrams, showing that they exist
in various brain regions and their content can be altered. These strategies have taken advantage of immediate
early genes (IEGs) such as Arc, which are expressed upon neuronal activation. Transgenic and viral tools,
such as the ArcCreERT2 mice and the Robust Activity Marking (RAM) system, have been engineered to label
cells in an activity-dependent manner. Although these tools have furthered our understanding of how a single
engram is represented in the brain, they have not been combined to label multiple engrams. Thus, this
research plan focuses on identifying multiple engrams in a single mouse and characterizing the synaptic
mechanisms underlying multiple engram storage. To achieve these goals, I have developed and characterized
a novel viral strategy that allows for the labeling of previously activated Arc+ ensembles. I have combined this
viral strategy with the ArcCreERT2 x enhanced yellow fluorescent protein (EYFP) mice to ultimately label
multiple Arc+ ensembles and visualize multiple engrams in a single mouse. Using this novel combinatorial
transgenic/viral strategy, I have shown that the engrams of exposures to a single environment are reactivated
to a greater extent those representing exposures to different environments. Moreover, the synaptic
mechanisms that contribute to the storage of multiple memories in the hippocampus is poorly understood. To
this end, during the F99 phase, I propose to use ex vivo electrophysiology to identify synaptic signatures (e.g.,
excitability, connectivity) of co-labeled Arc+ ensembles. A greater understanding of the synaptic properties of
the ensembles that are recruited to multiple engrams will contribute to our overall understanding of how
memories are co-stored in the brain. For the K00 phase, I will investigate the population-level dynamics of
hippocampal ensembles during memory processes using large-scale recording techniques and computational
models. These studies will illuminate our understanding of the computations performed by the hippocampus
that support memory processes and will allow us to generate more precise hypotheses for how these
computations might go awry in memory-related disorders, such as Alzheimer’s Disease (AD). The completion
of this research proposal will provide me with training in electrophysiology, strengthen my technical and
professional skills, and facilitate my transition to a postdoctoral position in a laboratory that studies population
dynamics of neural ensembles and computational methods.

## Key facts

- **NIH application ID:** 10541354
- **Project number:** 1F99NS129178-01
- **Recipient organization:** COLUMBIA UNIVERSITY HEALTH SCIENCES
- **Principal Investigator:** Michelle Stackmann
- **Activity code:** F99 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $47,752
- **Award type:** 1
- **Project period:** 2022-07-01 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10541354

## Citation

> US National Institutes of Health, RePORTER application 10541354, Generation of a dual transgenic/viral system to characterize multiple engrams in a single mouse (1F99NS129178-01). Retrieved via AI Analytics 2026-06-23 from https://api.ai-analytics.org/grant/nih/10541354. Licensed CC0.

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