Event-related brain potentials (ERPs) in schizophrenia for tonal and phonetic oddball tasks
Jürgen Kaysera,b, Gerard E. Brudera,b, Craig E. Tenkeb, Barbara .K. Stuartb, Xavier F. Amadora,c, Jack M. Gormana,c
a Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA
b Department of Biopsychology, New York State Psychiatric Institute, New York, NY 10032, USA
c Clinical Psychobiology, New York State Psychiatric Institute, New York, NY, USA
Received 16 June 2000; revised 18 October 2000; accepted 25 October 2000.
Abstract
Background: Prior studies using simple target detection ("oddball") tasks with pure tones have reported asymmetric reduction of the P3 event-related potential (ERP). This study investigated the time course and topography of ERPs recorded during both tonal and phonetic oddball tasks.
Methods: ERPs of 66 patients (14 unmedicated) diagnosed with schizophrenia (n = 46) or schizoaffective disorder (n = 20) and 32 healthy controls were recorded from 30 scalp electrodes during two oddball tasks using consonant-vowel syllables or complex tones. Overlapping ERP components were identified and measured by covariance-based principal components analysis.
Results: Schizophrenic patients showed marked, task-independent reductions of early negative potentials (N1, N2), but did not show reduced P3 amplitude or abnormal P3 asymmetry. Task-related hemispheric asymmetries of the N2/P3 complex were similar in healthy adults and schizophrenic patients. Poorer task performance in patients was related to ERP amplitudes, but could not account for reductions of early negativities.
Conclusions: The findings suggest that both patients and controls activated lateralized cortical networks required for pitch (right frontotemporal) and phoneme (left parietotemporal) discrimination. Task-independent reductions of negativities between 80 and 280 ms post-stimulus suggest a deficit of automatic stimulus classification in schizophrenia, which may be partly compensated by later effortful processing.
Key Words: Schizophrenia; event-related potentials (ERPs); N2/P3 complex; hemispheric asymmetries; tonal/phonetic oddball tasks; principal components analysis (PCA)