Peripheral auditory adaptation and fatigue: a model oriented review.

A model is introduced for auditory adaptation based on the stochastic models that are widely documented for birth and death processes and used as a vehicle to review single unit and compound action potential studies as well as various models for adaptation and forward masking. It appears that such a model inherently incorporates a relation between the perstimulatory adaptation time constant, the poststimulatory recovery time constant and the ratio between adapted firing rate and onset firing rate. The knowledge of any two of these parameters allows the prediction of the third one. The model takes into account postsynaptic membrane properties. The model based on Markov assumptions is a linear one. Although onset firing rates depend on a nonlinear way upon stimulus level, the above mentioned time constants and the adapted rate to onset rate ratio are intensity independent. The idea is put forward and tested that a comparable situation exists for the depression effects produced by mild auditory fatigue. The apparent findings that time constants tend to be intensity dependent for auditory fatigue is explained on basis of an interaction effect of dependent exponential processes.