Evoked potential correlates of psychosis.

Evoked potential (EP) correlates of several psychiatric disorders were investigated by applying a comprehensive EP procedure to 102 psychiatric patients and 28 nonpatients. EPs to left and right median nerve shocks, visual pattern flashes, and auditory clicks were recorded from one EOG and 14 monopolar scalp derivations. Nine age- and sex-matched groups were compared to yield the following main results: (i) EPs of overtly psychotic patients (schizophrenics, depressives, manics) differed markedly from normal, while those of patients without overt psychosis (neurotics, personality disorders, latent schizophrenics) did not; in the overtly psychotic, later EP events (100 msec or more poststimulus) were attenuated. (ii) EPs of neurotic depressives differed greatly from those of psychotic depressives. (iii) A somatosensory negative peak occurring 60-msec poststimulus (N60) was more posteriorly distributed in chronic schizophrenics (paranoid, undifferentiated) than in any other subject group. The attenuated later EP activity associated with overt psychosis was interpreted as a concomitant of cognitive (attention?) impairment, rather than of emotional disturbance.