Auditory evoked potentials in schizophrenic patients before and during neuroleptic treatment. Relationship to psychopathological state.

The auditory evoked potential (AEP) components N1 and P2 were investigated under a no-task condition in a group of 14 acutely ill unmedicated schizophrenic patients and compared with the findings in an age- and sex-matched control group. In the patients, N1 latency was significantly increased, P2 latency and N1-P2 interpeak latency were reduced. There were significant relationships between AEP parameters and the psychopathological state evaluated by means of the brief psychiatric ratings scale (BPRS). The N1 and P2 latencies were negatively correlated with the BPRS subscore "anergia" and positively correlated with "agitation". In 8 of the patients, a standardized neuroleptic treatment was started with 10 mg haloperidol/day. After 2 weeks of treatment, BPRS scores and N1 amplitude had significantly decreased. However, there was no relationship between BPRS improvement and N1 amplitude reduction. N1 latency in the unmedicated state was negatively correlated with subsequent therapeutic response measured as proportional improvement of the BPRS score within 2 weeks. Thus, N1 latency may be seen as a psychophysiological measure with prognostic applications.