# Validation and Optimization of Two-Photon Dendritic Voltage Imaging in Vivo

> **NIH NIH R34** · BAYLOR COLLEGE OF MEDICINE · 2024 · $333,000

## Abstract

PROJECT SUMMARY
Understanding information flow in cortical circuits requires understanding both the anatomical connectivity
between neurons and the way in which inputs to a neuron are integrated to generate a spiking output. Many
techniques are now available to study connectivity across cells and brain areas, but the dendritic integration of
these inputs is challenging to observe because we lack access to the complex electrical signals in fine dendrites.
The potential for fluorescent voltage sensors to revolutionize our understanding of the functional role of dendritic
integration in cortical circuits has been recognized for decades. However, in practice, fluorescent voltage sensors
have lacked the necessary characteristics in terms of brightness, sensitivity, and photostability to enable their
use in the challenging application of dendritic imaging in vivo. Furthermore, many fluorescent voltage sensors
are unsuitable for two-photon imaging, which is required to resolve dendrites at the scale of individual branches
and spines hundreds of microns deep in intact tissue. A new generation of genetically-encoded “JEDI” sensors
developed in the St. Pierre lab here at BCM overcome many of these limitations, and have now been validated
for two-photon somatic imaging in vivo. These validation experiments suggest that JEDI sensors have the
necessary sensitivity, photostability, and brightness to enable imaging of electrical activity in dendrites in vivo.
Complementing the development of these sensors, technologies for two-photon imaging of dendrites, including
adaptive optics for increasing spatial resolution and Bessel beam shaping for imaging sparsely-labeled dendrites
have been developed by the Ji lab at Berkeley. These techniques have been validated with dendritic calcium
imaging, but have not been combined with JEDI voltage sensors in dendrites in vivo. In this R34 proposal, we
will perform a careful series of validation measurements that will enable us to optimize advanced two-photon
imaging of JEDI voltage sensors for interrogating dendritic electrophysiology. These experiments will
unambiguously reveal the extent to which this approach has sufficient temporal and spatial resolution to enable
observations of key aspects of dendritic integration in vivo. Optimizing these techniques will be widely valuable
for the field, and will enable a future BRAIN Circuits project to answer fundamental questions about how
pyramidal neurons in primary visual cortex circuits integrate different sources of visual information in their
dendritic arbors, and how this process of integration is shaped by neuromodulators such as acetylcholine across
different brain states.

## Key facts

- **NIH application ID:** 10829452
- **Project number:** 5R34NS132045-02
- **Recipient organization:** BAYLOR COLLEGE OF MEDICINE
- **Principal Investigator:** Jacob Reimer
- **Activity code:** R34 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $333,000
- **Award type:** 5
- **Project period:** 2023-04-17 → 2026-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10829452

## Citation

> US National Institutes of Health, RePORTER application 10829452, Validation and Optimization of Two-Photon Dendritic Voltage Imaging in Vivo (5R34NS132045-02). Retrieved via AI Analytics 2026-07-02 from https://api.ai-analytics.org/grant/nih/10829452. Licensed CC0.

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