Tonotopic Arrangement of Narrowly Tuned Units in Primary Auditory Cortex

Abstract

Investigation of tuning characteristics of single units in AI of immobilized, unanesthetized cats revealed that about one-half of the units have narrow response ranges. Each electrode track was classified according to the characteristic frequencies (CF's) of its narrowly tuned units. The groups were: Tracks with unit CF's below 10 kHz, 10–20 kHz, 20–30 kHz, 30–40 kHz, and above 4:0 kHz. Track positions for each group were plotted on a standard cat cortex. There was considerable overlap between groups, and group centroid moved posteriorly for the lower frequencies. Results are in general agreement with Evans et al. [J. Physiol. 179, 238–247 (1965)]. After unit study, some cats were anesthetized and evoked “spikes” from 1×1-mm patches of strychnine-treated cortex were recorded for comparison with unit data. The strychnine-spike tuning characteristics corresponded to those of some but not all units under a patch. [Work supported in part by the Public Health Service, U. S. Department of Health, Education, and Welfare, and by the U. S. Air Force Office of Scientific Research.]