Response to contralateral and ipsilateral auditory stimulation from the same cortical areas

Abstract

Evoked responses were recorded from anesthetized cats from the subdivisions of the ‘auditory cortex’ to contralateral and ipsilateral stimulation with pure tones. Responses could be recorded from all subdivisions to either mode of stimulation. The area over which responses could be recorded to contralateral and ipsilateral stimulation overlap but the area over which contralateral responses could be evoked was more extensive. There is no consistent orientation of the points of largest responses nor of the response areas as shown by correlation data. For either mode of stimulation responses were largest in AI or AII but there was no consistent ordering of response amplitudes in the remaining subdivisions. Responses were, in most but not all cases, larger to contralateral stimulation in all subdivisions. No consistent ranking of latencies in the subdivisions was found for either contralateral or for ipsilateral stimulation. Latencies in AI were more apt to be shortest to contralateral stimulation. In the remaining cases the shortest latencies were not consistently found associated with contralateral stimulation. Thresholds were more apt to be lowest in AI and the second lowest thresholds were more apt to be found in AII for either contralateral or ipsilateral stimulation. There was no consistent ordering of thresholds in the remaining subdivisions. Comparison between contralateral and ipsilateral stimulation disclosed a difference in favor of contralateral stimulation in Ep alone where contralateral responses had lower thresholds.