Abstract
A phenomenological model for neural coding in the central auditory system is presented. This model is based on average rate-place codes and the hypothesis is that the rate-place code present in the population of low spontaneous rate nerve fibres is adequate to account for frequency discrimination thresholds across the entire audible frequency range. The activity of a population of nerve fibres in response to an input pure tone is calculated and a neural spike train pattern is generated. An optimal central observer estimates the input frequency from the spike train pattern. The model output is the frequency difference limen at the specific input frequency, determined from the estimated input frequency. It is shown that a rate-place code can account for psychoacoustically observed frequency difference limens. The model also supports the hypothesis that a human listener does not make full use of all the information relevant to frequency that is available in auditory nerve spike trains.
Highlights
A sound stimulus received by the peripheral auditory system is transformed to neuralspike train activity in a population of auditory nerve fibres
The model presented in this paper proposes a mechanism for the signal processing required for frequency discrimination
The model clearly shows, that the human observer does not make full use of all the information relevant to frequency which is available in the auditory nerve spike trains
Summary
A sound stimulus received by the peripheral auditory system is transformed to neuralspike train activity in a population of auditory nerve fibres (called a spike train pattern). Phase locking is progressively lost as stimulus frequency increases above about 2500 Hz (Delgutte, 1995) Both coding mechanisms probably operate in parallel over a large range of frequencies, but it is not clear yet to which extent the central auditory system uses either mechanism alone or both mechanisms simultaneously in the determination ofthe frequency ofa pure tone (Johnson, 1980). It is, known that at increasingly higher auditory nerve centres more phase-locking is lost and the auditory system relies increasingly on rate-place codes alone (Langner, 1992)
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