Opposite patterns of P300 asymmetry in schizophrenia are syndrome related.

In schizophrenia reduction of the P300 amplitude is a robust statistical finding but with inconsistent evidence of symptom correlates and of lateral asymmetry. Here relations were examined with active and withdrawn syndromes which in other cognitive and electrophysiological measurement modalities have been associated with opposite functional asymmetries. A standard oddball detection task was used to elicit auditory evoked potentials from dextral DSM-IV schizophrenic patients. On clinical ratings blind to the psychophysiology, eight were classified as withdrawn and 12 had a predominance of active syndrome features. Both patient groups had congruent P300 maxima at Pz or P4, attesting to their application to the detection task. Syndromes were differentiated by opposite asymmetries in P300, N200-P300 and N100 amplitudes at the posterior temporal sites: a reduction in P300 and N200-P300 amplitudes on the left in the active patients, and a reduction on the right in the withdrawn patients, with the opposite asymmetries in N100 amplitudes. The syndrome-related asymmetries in P300, also manifested in earlier attentional (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.