Widespread electrical cortical dysfunction in schizophrenia

The purpose of this study was to compare slow cortical electrical activity between healthy and schizophrenic individuals using 123-channel EEG and current density reconstruction (CDR). Twenty-nine healthy subjects and 14 drug-free patients performed three visual paired-associate tasks (verbal, pictorial and spatial). We modeled the generators of the slow potentials (SPs) at their peak amplitude by Lp-norm minimization using individual MRIs to model the volume conductor and source. Activity in each architectonic area of Brodmann was scored with respect to individual maximum current by a percentile method. Resulting scores by cortical area were analyzed by multivariate analysis of variance (MANOVA) with planned comparisons, to search for differences among levels. Results showed a multifocal pattern of current density foci comprising the SP generators, including frontal and posterior cortices in all subjects. A few cortical areas, not exclusively frontal, were observed to significantly differ between groups. Moreover, changes in patients' frontal activity were not exclusively to lower scores or 'hipofrontality': overall effects (all tasks collapsed) included increased electrical activity in right area 10, left 38 and 47 bilaterally, and decreased activity in right area 6 and left areas 39, 21 and 19. A few additional areas showed significantly altered activity only in particular tasks. We conclude that the present method, by preserving individual anatomical and functional information, indicates bidirectional patterns of altered electrical activity in specific cortical association areas in schizophrenia, which are not compatible with the exclusive 'hipofrontality' hypothesis. Our results agree with the hypothesis of schizophrenia as a syndrome resulting from abnormalities in multiple encephalic foci.