Neuronal responses of the primary auditory cortex in the Japanese monkey: Tonotopicity revisited

Abstract

The purpose of this study was to examine response patterns of neurons in the primary auditory cortex of the Japanese monkey anesthetized with nitrous oxide for better understanding sound processings in the central auditory system. White noise bursts and tone bursts were used as stimuli. Major findings are that neurons in the primary auditory cortex show 1) antero-posterior tonotopicity at threshold level, 2) complicated temporal response patterns depending on frequency and/or intensity at suprathreshold level and 3) few ON-responses. Results suggest that a neuron in the primary auditory cortex may respond to different frequencies by using different temporal response patterns; namely, different frequencies may be encoded during different time intervals. More, the present data imply the capability that a neuron in the primary auditory cortex may facilitatively respond to a complicated sound composed of sequentially presented different frequencies, such as speech sounds and natural sounds. Relationships between unit activities and the auditory evoked responses, including the auditory evoked neuromagnetic field, will be also discussed. © 1994, Acoustical Society of Japan. All rights reserved.