Effectiveness of aperiodic retinal stimulation in improving temporal visual cortical response.

Objective: Visual prostheses can provide partial visual function in patients with retinal degenerative diseases. However, in clinical trials, patients implanted with retinal prostheses have reported perceptual fading, which is thought to be related to response desensitization. Additionally, natural stimuli consist of aperiodic events across a short temporal span, whereas periodic stimulation (fixed inter-pulse intervals) is the standard approach in retinal prosthesis research. In this study, we investigated how aperiodic stimulation of the epiretinal surface affects electrically evoked responses in the primary visual cortex (V1) compared with periodic stimulation.

Approach: In vivo experiments were conducted in healthy and retinal-degenerated rats. Periodic stimulation consisted of constant inter-pulse intervals (IPIs), whereas aperiodic stimulation was provided by mixed IPIs. We calculated the spike time tiling coefficient (STTC) to assess response consistency across trials, the significant response ratio, and the spike rate to analyze response desensitization.

Main results: The results showed a significantly lower consistency of cortical responses in retinal degenerated rats than in healthy rats at 5 Hz. The consistency of the response to periodic stimulation decreased considerably as the frequency was increased to 10 Hz and 20 Hz in both groups and was greatly improved by applying aperiodic stimulation. In addition, aperiodic stimulation evoked a significantly higher spike rate in response to continuous stimulation at high frequencies (e.g., 10 and 20 Hz). Significance. By applying electrical stimulation with varying IPIs directly on the epiretinal surface, we observed promising results in terms of enhancing cortical response consistency and reducing desensitization. This finding presents a potential approach to enhance the effectiveness of retinal prostheses. .