Simulation of cochlea implant stimulation considering dispersive properties of the environment

Abstract

A computer numeric algorithm is used to simulate the time course of the electric field around a stimulating electrode of a cochlear implant. The dispersive properties of the surrounding biological tissues, i.e., the frequency-dependent conductivity and dielectric properties, are considered in the simulations. The study focuses on the polarization of auditory nerve tissue. It investigates how the polarization changes with pulse shapes that are typically used in cochlear implants. It is shown that several findings on the effect of pulse shape on the threshold and dynamic range can be predicted on the basis of the mean amount of this polarization. This approach also provides a possible explanation for why a change from a biphasic to triphasic pulse is able to reduce unwanted facial costimulation, which is sometimes observed in cochlear implant users.