Modelling research on different types of retinal ganglion cells for the formation of irregular phosphenes

Abstract

According to some clinical reports, prosthesis implant recipients perceived some irregular phosphenes, a phenomenon that does not have a definite explanation. One hypothesis points to the unwanted activation of passing axons and the differences in responses of various types of retinal ganglion cells as the cause of irregular phosphenes. The objective of this paper was to study the responses of different types of retinal ganglion cells through model-based epiretinal stimulation research in order to support this hypothesis. In this paper, a retinal stimulation model and six types of retinal ganglion cell computational models were established. We investigated the responses of each type of retinal ganglion cell model under stimuli with different polarities and pulse durations. According to our results, different types of ganglion cell models had various responses to anodic stimuli. In addition, when a modelled ganglion cell was activated by a monophasic cathodic impulse with a longer pulse duration, the ratio of the threshold of the distal axon and the minimum threshold of a retinal ganglion cell decreased. As a result, it was easier to activate the passing axon using a stimulus with a longer pulse duration.