A neural-counting model based on physiological characteristics of the peripheral auditory system. IV. Application to response of individual neural fibers

For part III, see Acustica (in press). An energy-based neural-counting model, incorporating refractoriness and spread of excitation, has recently been applied to intensity discrimination and loudness estimation for a variety of acoustic stimuli. In this model, refractoriness was the sole means of achieving the saturation effect of the afferent fiber´s response. Though refractoriness (or an effect like it) should be included in a proper Poisson-based model to produce a neural count variance less than the count mean (in accordance with experiment), there is a strong additional saturation effect associated with the response of the receptor. This earlier model is now extended to incorporate the effects of receptor saturation and spontaneous neural activity. In this paper the behavior of individual neural channels is investigated. Theoretical firing-rate curves are obtained as a function of stimulus level and frequency (isointensity contours). These are found to be in good agreement with neurophysiological data. It is shown that it is possible to fit human psychophysical tuning curves with a double-tuned linear filter, by judicious choice of the tuning parameter.