# Novel Multi-Depth Two-Photon Microscope for Measuring Neuronal Network Plasticity

> **NIH NIH R21** · UNIVERSITY OF CALIFORNIA, SAN DIEGO · 2020 · $591,330

## Abstract

PROJECT SUMMARY
 Faced with a continuous stream of data, the hippocampus must strike a balance between forming new,
discrete memories (pattern separation) and generalizing information across similar experiences (pattern
completion). Computational and experimental studies over the past 50 years have begun to delineate the
hippocampal circuits involved in these processes, yet a fundamental question is still unanswered: How do the
different subregions within the hippocampus integrate time-varying information during experience to form
episodic memories? Whether exploring a novel environment, scanning a visual scene, or recognizing a familiar
tune, the sensations used to construct and recall memories are not experienced simultaneously but rather as a
dynamic stream of information or temporal pattern. Our proposal seeks to understand how the hippocampus,
and in particular the dentate gyrus (DG) and CA1 subfields, integrate time-varying information during learning to
perform temporal pattern separation and completion. Understanding these mechanisms will provide crucial
insights into why our ability to learn and remember declines with age and how hippocampal pathology leads to
significant memory impairment in disorders such as Alzheimer’s disease.
 In order to understand how different subregions process temporal information and to fully capture learning
in real time, one must be able to measure activity within two or more networks simultaneously with single cell
resolution. In principle, this can be accomplished using two-photon calcium imaging of distinct neuronal
populations labeled with green and red fluorescence indicators respectively. However, many circuits in the
mammalian brain, including the hippocampus, are laminar where networks are separated by hundreds of microns
or more in depth. Microscope objectives are optimized to image only a single focal plane, and optical aberrations
severely degrade the laser excitation spot when large axial displacements of ~100 µm or greater from the
objective’s ideal focal plane are introduced. To overcome this challenge, we propose to construct a novel two
photon imaging system that utilizes both remote focusing and adaptive optics to focus two laser sources with
distinct excitation wavelengths at different arbitrary depths. This novel two-photon microscope will allow us to
record neuronal activity within both the CA1 and deeper DG subfields simultaneously for the first time,
investigating how these subregions process temporal information and modify network activity during learning

## Key facts

- **NIH application ID:** 10058191
- **Project number:** 1R21EB029139-01A1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN DIEGO
- **Principal Investigator:** Matthew Shtrahman
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $591,330
- **Award type:** 1
- **Project period:** 2020-09-01 → 2023-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10058191

## Citation

> US National Institutes of Health, RePORTER application 10058191, Novel Multi-Depth Two-Photon Microscope for Measuring Neuronal Network Plasticity (1R21EB029139-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10058191. Licensed CC0.

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