Pattern evoked potential measurements suggesting lateralized hemispheric dysfunction in chronic schizophrenics.

Visual evoked potentials (VEP) were measured to obtain evidence concerning possible lateralized hemispheric dysfunction in schizophrenia. The main results are based on the spatial distribution (12 electrodes) of a measure of VEP wave form stability over time. Subjects were 86 psychiatric inpatients and 33 nonpatients; these were grouped in three ways to permit comparisons of various age- and sex-matched diagnostic classes. Main findings were: (i) VEP wave form stability was generally lower in all types of schizophrenia than in nonpatients, nonpsychotic patients and, probably, psychotic depressives. (ii) VEP stability differed more between the hemispheres in schizophrenics and psychotic depressives than in nonpsychotic subjects; in schizophrenics, left hemisphere stability was lower than normal, whereas it was normal in psychotic depressives. (iii) VEP stability differences between the hemispheres were also greater than normal in latent schizophrenics, with less stability on the left. The results provide a direct demonstration of a left hemisphere involvement in schizophrenic dysfunction.