Influences of neural refractoriness on spatio-temporal spike with pulsatile electrical stimulation

This paper presents an analysis of the effects of neural refractoriness on the spike initiation properties of an auditory nerve fiber stimulated by two-pulse electric stimuli (masker and probe). This analysis was based upon results from a computational model of a mammalian auditory nerve fiber axon having 50 nodes of Ranvier, each consisting of stochastic sodium and potassium channels, making it possible to represent the temporal fluctuations of action potential initiation and conduction. In the present article, it is shown that as the shorten, the temporal jitter and relative spread tend to increase and the spatio-temporal histogram of spike initiations becomes wider. These results imply that refractoriness can enhance the randomness of spatio-temporal spike initiations. As temporal fluctuations are important for speech coding in cochlear implants, we conclude that refractoriness also plays a significant role in temporal coding of electrical stimuli.