Organization of Auditory Cortical Areas in Man

Average responses to clicks were recorded from the exposed human cortex of 19 adult patients during operation for the treatment of intracranial diseases. Auditory evoked responses were obtained from two areas. Short latency potentials were recorded on the superior surface of the temporal lobe corresponding to the transverse temporal gyri. These responses consisted of two positive waves P1 and P2 separated by a negative wave N1. P1 had a mean latency of 14-7+/-1-5 ms, N1 a mean latency of 19-1+/-2-6 ms and P2 a mean latency of 32-2+/-4-1 ms. Responses to stimulation of the contralateral ear were of higher amplitude than responses to stimulation of the ipsilateral ear. Responses of smaller amplitude and longer latency were obtained from the superior temporal gyrus and the upper lip of the sylvian fissure. These responses had a mean peak latency for P1 of 40-2+/-2-6 ms, for N1 of 62-5+/-12-5 ms and for P2 of 97-7+/-17-2 ms. It is concluded that the cortical auditory region of man may be subdivided in two major areas: an area on the supratemporal plane representing the primary auditory area or A1 and a region surrounding A1 which perhaps comprises two areas, one on the superior temporal gyrus and one on the upper bank of the sylvian fissure including frontal and parietal operculi.