Single-Unit Activity in the Primary Auditory Cortex of Unanesthetized Cats

Abstract

Activity of single cells in cats immobilized with gallamine triethiodide was recorded with metal microelectrodes and displayed by an on-line dot display. Tone burst, noise burst, click, and other stimuli at moderate intensities were presented through condenser microphones at both ears. Spontaneous activity ranged from less than 1 spike/sec to greater than 40 spikes/sec. Almost all units were affected by acoustic stimuli, either by enhancement of activity, reduction of activity, or a combination. Units were affected at the onset and/or termination of a stimulus, throughout a stimulus, or a combination. Best frequency of units ranged from less than 1 kHz to greater than 50 kHz. Over half the units responding to tone bursts exhibited a response range greater than 1/2 oct. Some units had double response ranges. The pattern of response to tone bursts of some units changed as the frequency of the stimulus was changed. A minority of the units showed responses only to special stimuli such as swept tones or continuous noise or tones. It appears that the coding of acoustic stimuli by single units of the primary auditory cortex of the cat is performed in a highly individualistic and variegated manner.