THE P50 COMPONENT OF THE AUDITORY-EVOKED POTENTIAL AND SUBTYPES OF SCHIZOPHRENIA

Decreased amplitude of the P50 component of the averaged evoked potent ial has been reported in schizophrenic patients. In an attempt to dete rmine the relationship of this decrease to subtype diagnosis, we compa red P50 amplitudes in 24 neuroleptic-free schizophrenic patients with paranoid (n = 13) versus nonparanoid (n = 11) subtype diagnoses. Eleve n normal subjects and 11 cocaine users served as control groups. The s chizophrenic patients were studied again after they had been treated w ith neuroleptics for 2 weeks. The control groups were studied again at least 2 weeks later. At baseline, the nonparanoid patients had signif icantly lower P50 amplitudes than did the normal subjects. The paranoi d patients did not differ from the normal control subjects. The cocain e users had significantly decreased P50 amplitudes as compared with th e normal control subjects. Neuroleptic treatment had no effect on P50 amplitudes in the paranoid patients but normalized amplitudes in the n onparanoid patients. The data suggest that P50 measurements may be use ful in identifying subtypes of schizophrenia.