Responses of Single Cortical Cells to Repetitive Clicks

Abstract

Intra- and extracellular recordings from single cells in the primary auditory cortex of unanesthetized cats were obtained using glass micropipets. Repetitive clicks were presented in trains of 500-msec duration. Over 100 units were systematically studied with click trains, single clicks, noise bursts, and tone bursts, presented 1/sec. 30% of the cells did not respond to repetitive clicks. These units did not respond to single clicks either, but responded to noise and/or tone bursts. 20% “followed” repetitive clicks with considerable scatter for rates up to 10–50/sec. Intracellular recordings from these cells showed stimulus-locked IPSPs for clicks. 30% followed repetitive clicks with precise locking with limiting rates of 10–1000/sec. These cells were “on” responders for tone and noise bursts and showed, when penetrated, a synchronization of EPSPs to repetitive clicks. The remaining 20% did not follow repetitive clicks but had click-rate-dependent responses, transient or sustained, to the trains. [Research supported in part by the National Institute of Neurological Diseases and Stroke and the U. S. Air Force Office of Scientific Research.]