Functional asymmetries in schizophrenia and their relationship to cognitive performance.

Previous accounts of cerebral dominance in schizophrenic patients have been conflicting. While many studies report decreased patterns of functional laterality in schizophrenic subjects, others report increases or no differences. Conceptual differences in the definition of laterality and its effects on behavior may be a reason for the poor concordance among studies. The present report addresses some of these problems and examines the hypothesis that schizophrenia may be associated with an alteration in normal patterns of functional laterality. In addition, the relationship between patterns of laterality and cognitive functioning was assessed. Twenty-one schizophrenic patients and 24 control subjects, all right-handed, were compared on two neuropsychological batteries, one designed to test cerebral dominance and the other, cognitive performance. Cerebral dominance was measured by two dichotic listening tests (verbal and nonverbal) and three motoric tests. Cognitive ability was assessed with a comprehensive neuropsychological battery. Schizophrenic and control subjects differed significantly in performance on laterality measures, but they did not differ in patterns of functional laterality when performance was taken into account. In addition, it was shown that the relationship between cognitive ability and laterality is complex, with some aspects of laterality appearing to be beneficial to cognitive ability.