A stochastic model of the electrically stimulated auditory nerve: Single-pulse response

Most models of neural response to electrical stimulation, such as the Hodgk in-Huxley equations, are deterministic, despite significant physiological e vidence for the existence of stochastic activity, For instance, the range o f discharge probabilities measured in response to single electrical pulses cannot be explained at all by deterministic models. Furthermore, there is g rowing evidence that the stochastic component of auditory nerve response to electrical stimulation may be fundamental to functionally significant phys iological and psychophysical phenomena, In this paper we present a simple a nd computationally efficient stochastic model of single-fiber response to s ingle biphasic electrical pulses, based on a deterministic threshold model of action potential generation. Comparisons with physiological data from ca t auditory nerve fibers are made, and it is shown that the stochastic model predicts discharge probabilities measured in response to single biphasic p ulses more accurately than does the equivalent deterministic model. In addi tion, physiological data show an increase in stochastic activity with incre asing pulse width of anodic/cathodic biphasic pulses, a phenomenon not pres ent for monophasic stimuli, These and other data from the auditory nerve ar e then used to develop a population model of the total auditory nerve, wher e each fiber is described by the single-fiber model.