Encoding of Frequency Information in the Discharge Pattern of Auditory Nerve Fibers

With micro-electrodes one can study the action potentials of single auditory-nerve fibres in their response to sound. It is well known that for pure tones the firing pattern of a neuron is very frequency-dependent. This selectivity is much more developed than is explainable from cochlear dynamics.We studied the response to white noise. The stimulus-response relation was studied with the help of the technique of the cross-correlation function. Action potentials were converted into uniform pulses and their average relation with the stimulus noise was computed by a Nuclear-Chicago Data Retrieval Computer (model 7100). This technique is possible for neurons with a characteristic frequency of less than 4 kHz. The firing of a neuron can then be shown to depend only on the frequency content of a sharply bounded frequency region of the noise. The boundaries of this region have approximately the same shape as the response region for pure tones mentioned above.For white noise, then, a cochlear neuron appears to be ...