Complex pitch perception after callosal section: Further evidence for a right hemisphere mechanism

Abstract

It has recently been suggested that right hemisphere auditory function provides a mechanism for complex pitch perception. This possibility was examined in two patients who underwent surgical section of the corpus callosum. Both patients were right handed, had bilaterally normal hearing, and were assessed to have left hemisphere language dominance. Each patient was tested using the Complex Tone Test, which consists of 112 trials in which a dichotic pair of 550-ms square wave stimuli are followed after 1 s by a binaural probe item. Subjects responded manually, indicating whether or not the probe matched either dichotic item. Both patients revealed above average accuracy on left ear stimuli, but performance on right ear stimuli that was significantly worse than chance. This pattern of results is similar to that found for dichotically presented speech stimuli, but in the opposite direction. These data add further support to the claim that the right hemisphere provides a mechanism for complex pitch perception. [Work supported by USPHS grant number 2 R01 NS15053-02 and the Alfred P. Sloan Foundation.]