A DUAL FILTER MODEL DESCRIBING SINGLE-FIBER RESPONSES TO CLICKS IN THE NORMAL AND NOISE-DAMAGED COCHLEA

This paper presents a composite model of the normal and noise-damaged guinea pig cochlea. The model incorporates a phenomenologically define d cochlear filter, and physiological descriptions of inner hair cell t ransduction, synaptic adaptation, and spike generation. The latter thr ee model sections were taken from recent literature. The paper first d eals with validation and evaluation of the model and adaptation of the relevant parameters to the guinea pig. Then the model is applied to e xplore to what extent changes in the cochlear filter can be held respo nsible for abnormal responses to clicks that were recorded in single a uditory nerve fibers in noise-damaged animals. Focus is on those fiber s in which the tip-to-tail sensitivity ratio of the frequency threshol d curve (FTC) has decreased and/or in which the FTC tail has become hy persensitive. Inspired by this type of W-shaped FTC the mechanical res ponse of the basilar membrane is phenomenologically modeled by two par allel filters, one responsible for the tip of the FTC, the other for i ts tail. Model simulations show that most abnormal temporal response p roperties can be explained by pathological alterations in the mechanic al response. Residual discrepancies between model and experiment are i dentified which presumably point to pathological changes in other stag es of cochlear processing.