# Relating spontaneous activity to electrical stimulation properties of primate retinal ganglion cells

> **NIH NIH F30** · STANFORD UNIVERSITY · 2020 · $39,154

## Abstract

Project Summary / Abstract
The most promising treatment option for photoreceptor degeneration, which is the leading cause of blindness
in the United States, are retinal prostheses that are surgically implanted on the anterior retina in order to gain
electrical access to the retinal ganglion cells (RGCs), bypassing the damaged photoreceptor cell layer. Despite
there being a few FDA approved epiretinal prostheses on the market, the high density of RGCs at the surface
of the retina makes it difficult to deliver current from electrodes with enough precision to recapitulate the natural
patterns of ganglion cell activity, and thus useful visual perception for blind patients. This is due to coarse
electrical stimulation that evokes unwanted activity in cells and axons at the epiretinal surface, especially in the
central retina where cells are the densest. The goal of this research is to use information from the natural RGC
activity recorded on the multi-electrode array in order to guide precise, spatially targeted electrical stimulation.
Careful application of the properties of electric fields propagating in tissue to calibrate stimulation currents will
allow epiretinal implants to produce meaningful visual perception in blind patients.
The relationship between the recorded signature of a given RGC’s activity on the array—its ​Electrical Image
(EI)—and its sensitivity to single or multi-electrode stimulation—its ​Electrical Receptive Field (ERF)—will be
determined. First, experiments will be conducted in peripheral primate retina to collect data on RGC activation
characteristics in response to delivering current from each of the ~500 electrodes on the array. Next, we will
extend this model to experimental data collected on the smaller, densely-packed RGCs in the central Raphe
region of the retina. Despite dense electrode spacing, arrays are limited in their ability to deliver precisely
targeted stimulation by the distance between electrodes. This can be addressed by weakly stimulating with
multiple neighboring electrodes at the time same, pushing the strength of stimulation current at the intersection
of the multiple generated electric fields over the threshold required for target RGC activation. We will stimulate
with combinations of two to seven neighboring hexagonally arranged electrodes to collect RGC ERFs in the
peripheral and central retina. An cascading linear-nonlinear model, popular for modeling neuronal spiking, will
be fit with EIs as input to predict ERFs across the array. A thorough understanding of the EI-ERF relation in the
retina will enable the closed-loop, precise, spatially localized stimulation necessary for designing a high-fidelity
epiretinal device, and uncover general principles applicable elsewhere in the central nervous system.

## Key facts

- **NIH application ID:** 10053233
- **Project number:** 5F30EY030776-02
- **Recipient organization:** STANFORD UNIVERSITY
- **Principal Investigator:** Sasidhar Madugula
- **Activity code:** F30 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $39,154
- **Award type:** 5
- **Project period:** 2019-09-01 → 2023-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10053233

## Citation

> US National Institutes of Health, RePORTER application 10053233, Relating spontaneous activity to electrical stimulation properties of primate retinal ganglion cells (5F30EY030776-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10053233. Licensed CC0.

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