Auditory event-related potentials and clinical scores in unmedicated schizophrenic patients

Event-related potentials (ERPs) have been widely examined in schizophrenic patients. However, although neuroleptic medication could be a potentially confounding variable, studies with unmedicated patients are relatively scarce. The present work was undertaken to determine whether ERP abnormalities persist in stabilized schizophrenic patients after drug withdrawal. In addition, ERP amplitudes and latencies were compared with clinical ratings (the Positive and Negative Syndrome Scale, PANSS) by means of Spearman rank order correlation coefficients. The P300 and N200 responses to rare tones and the P200 and N100 responses to frequent tones were recorded in 20 clinically stabilized drug-free schizophrenic patients and 19 age-matched control subjects during a two-tone discrimination task. Major findings were that the schizophrenic patients had reduced P300, N200 and N100 amplitudes and an increased P300 latency. The P300 amplitude was negatively correlated with age in patients. The P200 latency was negatively correlated with the PANSS positive syndrome score. The ERP abnormalities shown in this study appear to be enduring traits of the disorder as they persist in stabilized patients even after drug withdrawal.