P300 topography differs in schizophrenia and manic psychosis

Background: Overall and left temporal scalp area reductions of P300 have be en demonstrated in schizophrenia. P300 amplitude and topography in psychoti c affective disorder a crucial comparison in assessing the specificity of P 300 abnormalities to schizophrenia, are not well studied. Methods: P300 was recorded from 35 schizophrenic, 20 psychotic manic, and 3 0 control subjects. All were right-handed men. Results: P300 was reduced in both psychotic groups relative to control subj ects. Anteroposterior P300 topography differed between patient groups, with schizophrenic subjects showing posterior reduction and bipolar subjects sh owing anterior reduction. Schizophrenic subjects showed an abnormal asymmet ry, with smaller P300 over the left temporal scalp site than the right. Bot h bipolar and central subjects showed a left greater than right asymmetry. Conclusions: Widespread auditory P300 reductions were present in schizophre nia and bipolar disorder with psychosis, but subtle topographic differences were present in the two diseases. Although unequivocal knowledge of neural generators cannot be derived from topography alone, differences in topogra phy imply different generator configurations. Based an previous studies, th e posterior P300 reductions in schizophrenia may reflect abnormalities of a generator located in the left superior temporal gyrus. The frontal reducti ons in bipolar psychosis may reflect abnormalities in a hypothetical fronta l generator consonant with reports of altered frontal lobe function in mani a. Biol Psychiatry 1999;45:98-106 (C) 1999 Society of Biological Psychiatry .