Opposite patterns of P300 asymmetry in schizophrenia are syndrome related

In schizophrenia reduction of the P300 amplitude is a robust statistical fi nding but with inconsistent evidence of symptom correlates and of lateral a symmetry. Here relations were examined with active and withdrawn 'syndromes which in other cognitive and electrophysiological measurement modalities h ave been associated with opposite functional asymmetries. A standard oddbal l detection task was used to elicit auditory evoked potentials from dextral DSM-IV schizophrenic patients. On clinical ratings blind to the psychophys iology, eight were classified as withdrawn and 12 had a predominance of act ive syndrome features. Both patient groups had congruent P300 maxima at Pt or P4, attesting to their application to the detection task. Syndromes were differentiated by opposite asymmetries in P300, N200-P300 and N100 amplitu des at the posterior temporal sites: a reduction in P300 and N200-P300 ampl itudes on the left in the active patients, and a reduction on the right in the withdrawn patients, with the opposite asymmetries in N100 amplitudes. T he syndrome-related asymmetries in P300, also manifested in earlier attenti onal (N100) components are interpreted in terms of thalamo-cortical arousal systems having generalised, internalised influences, rather than in terms of later cognitive processes underpinning the P300, The findings endorse a syndromal approach to laterality research in schizophrenia. (C) 1999 Elsevi er Science B.V. All rights reserved.