Auditory and Visual P300 in Patients with Schizophrenia and Controls:

The P300 event-related brain potential (ERP) was employed to assess stimulus modality effects in patients with schizophrenia as compared to those in controls. The major purpose of this study was to assay frontal and temporal/parietal dysfunctions and characterize the resulting statistical effect sizes. Simple auditory and visual oddball stimulus discrimination paradigms were presented to patients with schizophrenia (N=20) and normal controls (N=20). The 2-stimulus auditory oddball paradigm was composed of a standard tone (1,000 Hz, 75 dB, 80%) and a target tone (2,000 Hz, 75 dB, 20%). The 2-stimulus visual oddball paradigm was composed of a standard stimulus (small circle, 80%) and a target stimulus (large circle, 20%). The P300 amplitudes in the schizophrenics were smaller than those in the controls for both modalities. The group differences produced larger effect sizes over the temporal/parietal areas than over the frontal areas in both the auditory and visual modalities. Although the patients with schizophrenia demonstrated smaller P300 amplitudes compared to the controls for both the auditory and visual stimuli, the strength of the modality difference was not significant. The P300 assessment of patients could be useful for further studies on temporal/parietal dysfunction, but the use of other paradigms for the evaluation of frontal dysfunction in schizophrenia should also be explored.