Coding of tonal stimuli by neurons in anterior auditory field of cat cerebral cortex

Abstract

In the cortex of barbiturate‐anesthetized cats, the anterior auditory field (AAF) was defined by microelectrode maps of its frequency organization, and the responses of single neurons in that field to monaural and binaural tone‐burst stimuli were examined quantitatively. AAF neurons generally had narrow, V‐shaped threshold frequency tuning curves centered on a clearly defined best frequency (BF). Intensity functions at BF were commonly monotonic in shape with dynamic ranges of 15 to 40 dB. Cells with nonmonotonic intensity functions had optimal sound pressure levels in the range 15 to 70 dB. Minimum response latencies at BF were in the range 10 to 15 ms. Binaural interactions were diverse, and a number of neurons demonstrated sensitivity to interaural intensity disparities. These properties are similar to those of cells in the primary auditory cortex, A1 [D. P. Phillips and D. R. F. Irvine, J. Neurophysiol. 45, 48–58 (1981)], and the data are consistent with the view that AAF and A1 function in some sense as parallel processors. It remains, however, to determine whether their thalamic afferents are independent, collateral, or overlapping, and to establish their specific functional roles in acoustic behavior.