Coding of time-varying sounds in the cochlear nucleus.

The results presented in the present paper show that single nerve cells in the cochlear nucleus have different discharge patterns in response to tones whose frequency varies rapidly compared to tones with slowly varying frequency. Moreover, small, rapid changes in the intensity of a tone are reproduced in such a way that a modulation of a few decibels can give rise to a nearly 100% modulation in the discharge pattern. Amplitude modulation is reproduced in the discharge pattern of these neurons throughout a large intensity range, in many units more than 70 dB. This intensity range is much larger than the intensity range where the mean discharge rate is a function of the sound intensity, meaning that changes in frequency as well as in intensity are enhanced in these units. Though no doubt but a small part of the processing that occurs in the cochlear nucleus, such information seems likely to be extracted somewhat differently by different neurons.