EVENT-RELATED POTENTIAL P300 MICROSTATE TOPOGRAPHY DURING VISUAL ONE-DIMENSIONAL AND 2-DIMENSIONAL TASKS IN CHRONIC-SCHIZOPHRENICS

Reports on left-lateralized abnormalities of component P300 of event-r elated brain potentials (ERP) in schizophrenics typically did not vary task difficulties. We collected 16-channel ERP in 13 chronic, medicat ed schizophrenics (25 +/- 4.9 years) and 13 matched controls in a visu al P300 paradigm with targets defined by one or two stimulus dimension s (C1: color; C2: color and tilt); subjects key-pressed to targets. Th e mean target-ERP map landscapes were assessed numerically by the loca tions of the positive and negative map-area centroids. The centroids' time-space trajectories were searched for the P300 microstate landscap e defined by the positive centroid posterior of the negative centroid. At P300 microstate centre latencies in C1, patients' maps tended to a right shift of the positive centroid (p < 0.10); in C2 the anterior c entroid was more posterior (p < 0.07) and the posterior (positive) cen troid more anterior (p < 0.03), but without left-right difference. Dur ation of P300 microstate in C3 was shorter in patients (232 vs 347 ms; p < 0.03) and the latency of maximal strength of P300 microstate incr eased significantly in patients (C1: 459 vs 376 ms; C2: 585 vs 525 ms) . In summary only the one-dimensional task C1 supported left-sided abn ormalities; the two-dimensional task C2 produced abnormal P300 microst ate map landscapes in schizophrenics? but no abnormal lateralization. Thus, information processing involved clearly aberrant neural populati ons in schizophrenics, different when processing one and two stimulus dimensions, The lack of lateralization in the two-dimensional task sup ported the view that left-temporal abnormality in schizophrenics is on ly one of several task-dependent aberrations.