OFF Types of Mouse Retinal Ganglion Cells Are Less Sensitive to a Change in Electric Stimulus Charge Than on Type

Abstract

For individuals blinded by retinitis pigmentosa or age-related macular degeneration, retinal prosthetic devices can restore some form of useful vision. Unfortunately however, their performance varies considerably across subjects and the best performance has not yet reached the level of legal blindness. It has been thought that the limitation of retinal prostheses comes from the lack of comprehensive understanding about how various types of retinal ganglion cells (RGCs) respond to an identical electric stimulus as well as about how changes in stimulus parameters alter their response patterns. In particular, it is crucial to better understand spiking patterns of ON and OFF types of RGCs in response to electric stimulation because these two types are known to be critical in forming visual percepts. Our previous studies reported that the two types have different sensitivities to changes in various stimulus parameters such as stimulation rate and stimulus duration, suggesting a possibility of similar difference in response to other changes. In this paper, we explored response changes of ON and OFF types of alpha RGCs to varying stimulus charges. We found that, at a fixed current amplitude, the response magnitudes of OFF types of alpha RGCs are minimally altered by doubled stimulus charge while those of ON RGCs are significantly altered by the same change. This finding may be used for optimizing overall retinal responses to electric stimulation for better artificial vision.