New perspectives in auditory coding: Bases for a new cochlear behavioural model

Abstract

In this paper we present a computational model of the auditory system, called “stable pulse correlation”, that was developed at the CNM. In the model, the cochlear system has been considered as a black box, incorporating some non very complex devices based on structural elements in the cochlear system itself. First of all, we consider a bandpass filter (basilar membrane) and some transduetor units (inner hair cells), whose behaviour could be defined by some specific parameters such as threshold, absolute and relative refractory period, and relaxation function. Our model considers that the output coded response to a particular single tone input signal will be given by the frequencies and the number of the generated stable states of a short number of different output signals and their correlations. A graphic output with 8this information could be extracted from the model (VARG diagram). This graph uses data obtained from the numeric model. The model and associated VARG diagram allows a close prediction of the cochlear behaviour to a specific excitation under certain limits. The results obtained are compared with experimental response of the auditory fibers and the auditory system under normal conditions. From this comparison we have a validate model that could be used as a cochlear system simulation model. In summary, we propose a new theory for auditory system encoding signals that could be applied to cochlear implant systems as well as to speech recognizers.