Effect of temporal lobectomy on binaural integration of dichotic tones

Abstract

Recent studies of the phenomenon of ear dominance for pitch have shown that 66%–75% of normal‐hearing subjects exhibit a left‐ear dominance when tested with dichotic tone pairs of 1650–1750 Hz. Since a previous report [Efron et al., Brain and Language 4, 537–549 (1977)] indicated that ear dominance might be related to an (asymmetrical) function of the cerebral cortex, the present experiments measured the direction and magnitude of a subject's ear dominance before and after an anterior temporal lobectomy (for chronic epilepsy). In all nine subjects tested, the lobectomy decreased the contribution of the pitch signal in the ear contralateral to the side of the lobectomy. Thus, depending on the subject's pre‐operative ear dominance and the side of the lobectomy, his post‐operative ear dominance was expected to either increase or decrease in magnitude. The specific prediction for each of the nine subjects was confirmed. The results demonstrate an important role played by temporal neocortex on the binaural integration of pure tone dichotic stimulation.