A mathematical modeling research for effects of electric stimulus waveforms on the excitability of optic nerve fibers

Visual prosthesis based on penetrative optic nerve (ON) stimulation is an alternative approach to partially restore visual function. As one of the most important factors, pulse shape of electrical stimulus is a major consideration in the design of ON visual prosthesis. Animal experiments showed that the evoked responses in visual cortex (V1) to ON electrical stimulation are dependent on the stimulus. The purpose of this research is to study the response properties of ON fibers under electrical stimulation in different shapes by mathematical modeling, in order to explore and explain the response mechanisms of ON to varied external electrical stimuli. Based on a mixed model of penetrating electrode and multiple ON fibers, we investigated the performance of a variety of stimulus waveforms in recruiting ON fiber responses by calculating recruitment area (RA). The simulation results provided a preliminary explanation for the V1 response properties to various ON electrical stimuli in the previous animal study. Besides, theoretical basis is formed for further design and choice of stimulus waveform in ON prosthesis.