Retinal degeneration (rd) leads to progressive photoreceptor cell death resulting in vision loss. Stimulation of the inner retinal neurons by neuroprosthetic implants is one of the clinically approved vision restoration strategies providing basic visual percepts to blind patients. However, little is understood to what degree the degenerating retinal circuitry and the resulting aberrant hyperactivity may prevent the stimulation of physiological electrical activity. Therefore, we electrically stimulated ex vivo retinas from wild type (C57BL/6J) and blind (rd10 and rd1) mice using an implantable subretinal microchip and simultaneously recorded and analyzed the retinal ganglion cell (RGC) output with a flexible microelectrode array. We found that subretinal anodal stimulation of rd10 retina and of wt retina evoked similar spatiotemporal RGC spiking patterns. In both retinas electrically stimulated ON and a small percentage of OFF RGC responses were detected. The spatial selectivity of the retinal network to electrical stimuli reveals an intact underlying network with a median receptive field center of 350 µm in both retinas. An antagonistic surround is activated by stimulation with large electrode fields. However, in rd10 and to a higher percentage in rd1 retinas rhythmic and spatially unconfined RGC patterns were evoked by anodal or by cathodal electrical stimuli. Our findings demonstrate that the surviving retinal circuitry in photoreceptor-degenerated retinas is preserved in a way allowing for the stimulation of temporally diverse and spatially confined RGC activity. Future vision restoration strategies can build upon these results but need to avoid evoking the easily inducible rhythmic activity in some retinal circuits.
- photoreceptor degeneration
- retinal network
- neuroprosthetic stimulation
- Copyright © 2015, Journal of Neurophysiology