Multi-electrode stimulation and recording in the isolated retina

As part of an exploration of the feasibility of an epi-retinal prosthesis, we developed an experimental method to electrically stimulate and record fr om retinal neurons using a micro-fabricated multi-electrode array. An isola ted retina is placed on an array of 10 mu m diameter disk electrodes with t he ganglion cell side of the retina facing the electrode surfaces. The reti na is bathed in oxygenated Ames' medium and warmed in order to sustain it i n vitro for the duration of an experiment. typically 4-9 h. To reduce stimu lus artifacts, the electrodes are grouped into two clusters - one used for stimulation and the other for recording - spaced several hundred microns ap art, and electrodes are insulated with both silicon nitride and a 10 mu m t hick layer of polyimide. Stimuli are delivered to the array using an optica lly isolated current source stimulator, and the resulting responses recorde d with an eight channel nerve response amplifier. Stimulation and recording are performed under computer control. A variety of physiologic measurement s is described in order to illustrate the strengths and drawbacks of this m ethod. (C) 2000 Elsevier Science B.V. All rights reserved.