Toward fractal coding in auditory prostheses
نویسندگان
چکیده
Fractal-rate behavior is a ubiquitous and important aspect of normal mammalian cochlear-nerve activity, which may well be absent in nerve bers excited by present cochlear prostheses. We propose simple methods for introducing fractal uctuations into a cochlear prosthesis, thus providing the natural statistical character of eighth-nerve ber spike trains. Fractal behavior is ubiquitous in mammalian cochlear-nerve activity. 1 All single-unit recordings of suucient length examined to date, in both the chinchilla 2 and the cat, 3 exhibit fractal uctua-tions, as evidenced by a number of statistical measures. The periodogram and the relative variance of the number of counts, for example, 4 show that nonfractal models such as the refractoriness-modiied Poisson process fail to give results that accord with the data. Rather, fractal models are required. 1?6 One of the simplest statistics that shows the fractal nature of this activity is the rate. The rate of a particular cochlear-nerve ber (CNF) may be estimated by dividing a neuronal recording into M equal, contiguous windows of duration T seconds each, and counting the number of action potentials N k that fall within the k-th window for all k between 1 and M. The rate estimate c k for 1
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