Event-related brain potentials (ERPs) in schizophrenia for tonal and phonetic oddball tasks

Background: Prior studies ruing simple target detection ("oddball") tasks w ith pure tones have reported asymmetric reduction of the P3 event-related p otential (ERP). This study investigated the time course and topography of E RPs recorded during both tonal and phonetic oddball tasks. Methods: Event-related potentials of 66 patients (14 unmedicated) diagnosed with schizophrenia (n = 46) or schizoaffective disorder (n = 20) and 32 he althy adults were recorded from 30 scalp electrodes dilling tnto oddball ta sk using consonant-vowel syllables or complex tones. Overlapping ERP compon ents were identified and measured by covariance-based principal components analysis. Results: Schizophrenic patients showed marked, task-independent reductions of early, negative, potentials (N1, N2) brit not reduced P3 amplitude ol ab normal P3 asymmetry. Task-related hemispheric asymmetries of the N2/P3 comp lex were similar in healthy adults and schizophrenic patients. Poorer task performance in patients was related to ERP amplitudes, but could not accoun t for reductions of early, negafivifies. Conclusions: The findings suggest that both patients and control subjects a ctivated lateralized cortical networks required for pitch (right frontotemp oral) and phoneme (left parietotemporal) discrimination. Task-independent r eductions of negativities between 80 and 280 msec after stimulus onset sugg est a deficit of automatic stimulus classification in schizophrenia, which may be partly compensated by later effortful processing.