Auditory P300 event-related potentials and neuropsychological performance in schizophrenia and bipolar affective disorder.

The auditory P300 event-related potential (ERP) and performance on neuropsychological tests were evaluated in 26 subjects with schizophrenia, 19 with bipolar affective disorder, and 27 controls. The schizophrenic and the bipolar groups were similar in having prolonged P300 latency recorded from central and temporal leads. The P300 was significantly reduced in amplitude in the schizophrenic group at midline leads and the left temporal lead but was not significantly reduced in amplitude at any electrode site when the bipolar group was compared to controls. Schizophrenics performed significantly less well than bipolars and controls on tests of verbal fluency and, within this group, a significant correlation was found between the latency of P300 and verbal fluency test scores. While the bipolar group of patients was similar to the schizophrenic group in having prolonged P300 latency, these groups differed in P300 amplitude, performance on verbal fluency tests, and the relationship between the physiological and neuropsychological variables.