Event-related potentials in schizophrenic patients during a degraded stimulus version of the visual continuous performance task

Previous studies of the auditory P300 event-related potential (ERP) have re ported smaller amplitudes in chronic schizophrenics but similar consistenci es have not been observed with visual P300s. This study examined P300s in s ymptomatically stable, medicated, chronic schizophrenics (n = 14) and norma l controls (n = 14) performing a visual continuous performance task utilizi ng degraded stimuli to burden encoding processes. Performance analysis foun d slower response times, fewer target detections and more false alarms in p atients than in controls. Analysis of ERPs showed P300 amplitudes of schizo phrenics to be significantly smaller than those of controls and, unlike con trols, schizophrenics failed to exhibit significant target vs. non-target P 300 amplitude differences. Discriminant analysis indicated target and non-t arget midline (F-Z, C-Z, P-Z) P300 amplitudes together correctly classified all patients and controls. Exploratory topographic analysis indicated that P300 amplitudes were not asymmetrical in patients, as has been observed wi th auditory P300s, and, unlike the performance measures, the P300s did not correlate with the patient's positive or negative symptom ratings. The impl ications of these findings are described in relation to attentional disturb ances and trait versus state issues in schizophrenics. (C) 1999 Elsevier Sc ience B.V. All rights reserved.