Perceptual asymmetry in schizophrenia and affective disorder: Implications from a right hemisphere task

The patterns of perceptual asymmetry exhibited by normal, schizophrenic, and affectively-disordered subjects on a dichotic tonal discrimination task, were compared. Affectively-disordered subjects' performances differed significantly from those of normal subjects, with normals demonstrating the expected left ear advantage, and affectively-disordered subjects showing no lateral advantage. The performance of the schizophrenic subjects fell between those of the normal and affective groups along a laterality continuum, with paranoid schizophrenic subjects tending to show a larger left ear advantage than non-paranoid schizophrenic subjects. The results do not support the hypothesis that schizophrenic subjects inappropriately transfer processing of right hemisphere stimuli to the left hemisphere, but do suggest that subgroup distinctions may be relevant to hypotheses of lateralized dysfunction in schizophrenia. Further, the performance of the affective group supports previous findings of right hemisphere abnormalities in affective disorder.