Effect of the Aperiodic Electrical Stimulation on the Visual Cortical Neuronal Response

In patients with retinal degenerative illnesses such as retinitis pigmentosa and age-related macular degeneration, retinal prosthesis shows the potential to restore partial vision. The natural stimuli are the aperiodic events distributed across a short time span. However, most studies commonly used periodic stimulation. Even though some in vitro studies explored the effect of aperiodic retinal stimulation on the retina ganglion cells' membrane potential, it still needs to understand how the aperiodic electrical stimulation on the retina affects the response in visual cortex. This study investigated how aperiodic retinal stimulation affects the electrically evoked cortical response compared with periodic stimulation in Sprague Dawley (SD) rats. We found that the aperiodic retinal stimulation evoked a significantly higher spike rate than the periodic pattern, especially at high frequencies (10 and 20 Hz). The spike rates showed a more significant difference between the periodic and 10% noise stimulation (P = 0.0013 at 20 Hz, two-tailed paired t-test) at 20 Hz stimulation. Regarding the temporal precision of responses, the responses to aperiodic stimulation showed higher temporal precision compared to periodic stimulation. The response to some stimulation pulse numbers under 10 and 20 Hz 50% noise and Poisson pattern stimulation was higher than the response to the first pulse. However, at the same frequency, the response to some stimulation pulse numbers under periodic stimulation was lower than the response to the first pulse. These findings raised a possible way to increase the response level and the temporal precision of the electrically evoked response.Clinical Relevance- This suggests that using aperiodic stimulation in retinal prostheses can increase electrically evoked response levels and temporal precision.