Average reference EEG lateralization in schizophrenic patients.

The authors transformed 9 channels of electroencephalogram (EEG) to 10 channels of average reference data and compared EEG asymmetry between medication-free (for 2 weeks) schizophrenic male patients (n = 14), male patients with affective disorder (n = 9), and normal males (n = 13). Multivariate analyses failed to find lateralized differences between groups in resting and task EEG. Neuroleptic treatment (n = 11) was associated with asymmetrical changes in beta power rather than in alpha and theta, as previously reported. There were no relationships between clinical ratings (based on the Brief Psychiatric Rating Scale and subscales) and alpha asymmetry. The authors discuss conflicts with previous findings and the advantages of minimizing reference bias when studying EEG topography.