EXCITATORY AND INHIBITORY RESPONSE AREAS OF AUDITORY NEURONS IN THE COCHLEAR NUCLEUS

Abstract

Responses to tones and bands of noise were recorded from single units in the cochlear nucleus of anesthetized cats. By varying the frequency and intensity of a 200 msec tone in small steps, the behavior of a unit was systemically sampled inside and outside the response area delimited by the thres-hold-versus-frequency tuning curve. Changes in stimulus parameters caused marked variations in the temporal patterns of discharge, often resulting in shifts from sustained firing to various patterns of intermittent firing. Bands of noise outside excitatory response areas were used to inhibit response to simultaneously delivered tones. Used alone, bands of noise centered at the best frequency were observed to inhibit the discharge of some units when the noise bandwidth was widened sufficiently. In contrast to the conventional picture of adaptation as an asymptotic decline in rate, profound and long-lasting modifications in adaptive behavior were observed in response to small changes in stimulus parameters. From the findings on single neurons, inferences are drawn as to some aspects of the response of populations of neurons.