A functional model of the hair cell-primary fiber complex

A model is proposed containing three parallel systems; system 1 is a single channel consisting of an inhibitory circuit being fed by a fixed permeability responsible for spontaneous activity in parallel with a displacement-driven permeability, while systems 2 and 3 each consist of a number of identical permeability-volume-permeability channels with on/off switches activated at levels specific for each channel. The (continuous) output of each system drives a Poisson generator whose output "events" are delivered to a firing mechanism in the form of a "leaky integrator" delivering actual "firings" in simulated real time. The model quite accurately reproduces (1) stimulation and recovery phases of PST histograms obtained at six levels of stimulation for six auditory fibers (including "dead" period after stimulation), (2) single-exponential functions of recovery from adaptation for both onset and steady-state part of probe tone, (3) increments in response as independent of time of application of stimulus increment, (4) a specified hazard function for firings, (5) interval histograms of driven activity, (6) loss of phase locking with increasing frequency of stimulation, and (7) extended dynamic range for onset of response. The model fails in reproducing specific characteristics for response to decrements, and for response to AM.