Longitudinal Study of P3a Potential in First-Episode Schizophrenia

P3a is an event-related potential that reflects the involuntary orienting of attention to salient stimuli. Abnormalities in P3a have been described in schizophrenia, but it is not known when they arise over the course of illness and whether they are progressive. Previous longitudinal studies of P3a have been inconclusive because of the heterogeneity in the diagnosis of psychotic patients, lack of follow-up data on controls, and relatively short follow-up periods. P3a, elicited by novel sounds, was assessed in 21 patients with first-episode schizophrenia and 36 healthy controls at baseline and reassessed in 14 patients and 23 controls after an average follow-up of six years. The longitudinal evaluation showed that the P3a amplitude was reduced in patients compared to controls at baseline but did not differ between groups at follow-up. Although P3a was reduced over the six-year interval in both groups, the reduction was greater in controls compared to patients. Longitudinal findings suggest that the P3a amplitude deficit is present at the onset of schizophrenia. Normalization of P3a amplitudes in patients at follow-up may reflect the premature aging effect on P3a at the onset of illness, a floor effect in P3a amplitudes of both groups at follow-up, or the reversal of the P3a deficit in patients over time. Interestingly, at baseline, the P3a amplitude in patients without follow-up data did not differ from controls and was greater than in patients with follow-up data. Baseline findings indicate a heterogeneity within the first-episode schizophrenia group.