The effect of laterality of stimulus presentation on auditory P300 topography in schizophrenia

Reduced P300 amplitude in schizophrenia has been a consistent finding. Recent studies have raised the question of characteristic topographic distribution. This study reports the effects of binaural and unilateral stimuli on the P300 topography in schizophrenia. An auditory "oddball" paradigm was repeated 3 times with left, right and binaural stimulation. Data were recorded using a 19-electrode montage with linked ear reference. Subjects were 18 untreated, hallucinating, paranoid patients with schizophrenia and 24 healthy matched volunteers. For the control subjects, stimulus conditions had no effect on P300 topography. For the sample with schizophrenia, topography under unilateral left stimulation resembled that of control subjects. Binaural and right-sided stimulation shifted peak amplitudes to the right and frontally. In addition to the usually observed parietal peak, a second P300 maximum having a different time course appeared over right frontal areas. The data provide further support for lateralized dysfunction in schizophrenia.