Response Profiles of Retinal Ganglion Cells to Sinusoidal Electric Stimulation vary for Low vs. High Frequencies.

Microelectronic retinal prostheses electrically stimulate retinal neurons with the goal of restoring vision in patients blinded by outer retinal degeneration. Despite some success in clinical trials, the quality of vision elicited by these devices is still limited. To improve the performance of retinal prostheses, our group studied how retinal neurons respond to electric stimulation. Our previous work showed that responses of retinal ganglion cells (RGCs) are frequency-dependent and different types of RGCs can be preferentially activated with a specific frequency and current amplitude. In the present study, we systemically examined responses of RGCs to sinusoidal electric stimulation with varying frequencies and amplitudes. We found that ON sustained alpha RGCs show distinct stimulus-response relationships to low and high frequency stimulation. For example, RGCs showed monotonic response curves to 500 Hz sinusoidal stimulation, whereas they showed non-monotonic response curves to 2000 Hz stimulation. We also described how increasing stimulus frequency gradually changed the response curves of RGCs.