Temporal P300 asymmetry in first episode schizophrenia

Abstract

event-related brain potentials (ERPs) are examined to uncover electrocortical correlates of cognitive or behavioral characteristics in schizophrenic patients. While smaller amplitudes of several ERP-components have been repeatedly reported for schizophrenic patients versus control groups, a larger slow surface-negative potential following the completion of a forewarned (motor or cognitive) response, called postimperative negative variation (PINY), has been reliably found in schizophrenic patients by several authors, but only rarely in healthy subjects. In a series of studies we examined contributions to the PINY by varying task-related features in visual and auditory delayed-matching-to-sample tasks in groups of schizophrenic patients (DSM-II1-R) and healthy controls. While demands on working memory enhanced PINY amplitude primarily in schizophrenic patients, PINV amplitude increased with ambiguity of the matching in controls and schizophrenics alike. Differential effects of ambiguity and performance requirements (Go-NoGo) on PINY amplitude and its scalp distribution suggest that performance uncertainty contributes to PINV generation and that the threshold for performance uncertainty is reduced in schizophrenics. Topographical analyses suggest that the PINY is generated symmetrically in the frontal lobes in schizophrenics, while it shows a right frontal dominance in controls. Research was supported by the Deutsche Forschungsgemeinschaft (Ro 805).