Development of a Model of the Electrically Stimulated Auditory Nerve

Cochlear Implants (CIs) are used to restore the sense of hearing in people with profound hearing loss. Some CI users can communicate over the phone and even understand speech with some background noise, however some other CI users do not obtain the same benefit from the device. One possible reason that might explain this variability, at least partially, is the individual differences in the interface created between the electrodes and the auditory nerve. For example the exact position of the electrodes in cochlea and the amount of functional auditory neurons might differ significantly for differnet CI users. In order to understand the electrode-nerve interface, a model of the auditory nerve activity stimulated by a cochlear implant has been developed. The model is based on existing models found in the literature. This paper presents the basic components of the model: Voltage distribution in the cochlea based on finite element method and auditory nerve model based on a multi-compartment Hodgkin Huxley equations. The model has been used to simulate 1) the extracellular voltage applied to the auditory nerve fibers and 2) the auditory nerve activity, produced by simple stimuli (single pulses) and complex stimuli (speech sounds) for different electrode configurations.