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You are here: McMaster Institute for Music and the Mind > Publications > A mathematical analysis of sound coding in the auditory nerve: spatiotemporal summing mechanisms

Ian C Bruce, L S Irlicht, and Graeme M Clark (1995)

A mathematical analysis of sound coding in the auditory nerve: spatiotemporal summing mechanisms

In Proceedings of 2nd Annual Joint Conference on Information Sciences, 9(894).

An understanding of mechanisms by which the human auditory system codes acoustical information has application to automated speech recognition and cochlear implants. In this paper, we formulate and analyze a mathematical model of the auditory system. The results are used to evaluate certain key theories of intensity and frequency coding. The peripheral auditory system codes sound properties in the firing patterns of the auditory nerve (AN). The 30,000 AN fibers are each tuned to a particular frequency of sound, and the response of each fiber is a sudden jump in its electrical potential known as a spike or action potential (AP). Since these spikes are largely identical, sound properties must be encoded by the place and timing of the spikes. Many theories of intensity and frequency coding reflect the convergence of groups of AN fibers on individual neurons of the brain stem by assuming spatial summation of nerve fiber activity [7][8]. This motivates the analysis of population, or summed responses. However, due to the large number of fibers in the AN, physiological investigations of such responses are quite difficult. Mathematical models can easily deal with summed stochastic systems, and can also be used to determine the information content of various aspects of neural firing patterns [4]. In order to best achieve this, the model developed here is general enough to encompass a wide range of coding theories, analytical to facilitate investigation of information content and parametric to permit such an investigation under various scenarios. Previous models such as that of [1] show the validity of summing mechanisms, but do not combine all the desired features.

auditory nerve, spatiotemporal summation, sound coding