Source distribution of neuromagnetic slow waves and MEG-delta activity in schizophrenic patients

Background: Schizophrenic patients exhibit more activity in the electroence phalographic delta and theta frequency range than do control subjects. Usin g magnetic source imaging (MSI) our study aimed to explore this phenomenon in the magnetoencephalogram (MEG), the distribution of its sources, and ass ociations between symptom profiles and sources of low-frequency activity in the brain. Methods: Whole-head MEG recordings were obtained from 28 schizophrenic pati ents and 20 healthy control subjects during a resting condition. The genera tors of the focal magnetic slow waves were located employing a single movin g dipole model. Distributed or multiple delta and theta sources were captur ed by the minimum norm estimate. Results: Both localization procedures showed slow wave activity to be enhan ced in schizophrenic patients compared with control subjects. Focal slow wa ve activity differed most between groups in frontotemporal and in posterior regions. Slow wave activity was associated with symptom characteristics in that positive symptoms varied with frontal delta and theta activity. Conclusions: Results indicate that activity in low-frequency bands in schiz ophrenic patients exceeds the activity of control subjects in distinct area s, and that this focal clustering of neuromagnetic slow waves may be relate d to psychopathologic characteristics. (C) 2001 Society of Biological Psych iatry.