Abstract
Purpose::
This work is related to the efforts of the Boston Retinal Implant Project to develop a sub-retinal prosthesis to restore vision to the blind. The specific purpose of this presentation is to demonstrate a method to better understand the population responses of retinal ganglion cells (RGCs) to various durations and intensities of photic stimuli, using a multielectrode array. The goal is to better understand the responses of RGCs to light in order to mimic these responses electrically by a retinal prosthesis.
Methods::
Extracellular recordings of action potentials of RGCs were made in superfused New Zealand White rabbit retinas using a multielectrode array. The cells were stimulated by flashes of light at different levels of illumination and stimuli durations. The photic stimulus durations were 10 msec, 100 msec, and 1000 msec. The relative illumination levels were 1 (full), 1/4, 1/8, and 1/32. The stimuli were applied to the whole retina uniformly. The data collected at the different recording electrodes were analyzed by dedicated software to sort the action potentials and measure temporal parameters of the responses.
Results::
Most recordings to date have been from ON-center RGCs. The responses of these cells to light onset included a short-latency (~30 msec) group of action potentials, followed by a second burst of action potentials that occurred about 60 msec following stimulus onset. The cells’ responses to light offset included a single or double burst (~ 90 msec to 400 msec following stimulus offset). Like ON-center RGCs, OFF-center RGCs also generated bursts of action potentials to flashes of light.
Conclusions::
The results show that RGC responses to a full-field photic stimulus consists of multiple bursts that occur at delays from about 30 to 400 msec relative to stimulus onset or offset. The responses are qualitatively similar to what has been described for electrical stimuli applied to retinas.
Keywords: retina • retinal connections, networks, circuitry