Dynamic event-related potentials and rapid source analysis reveals an intermittent short-lasting dysfrontality in schizophrenia

Neuroimaging studies have identified regional brain dysfunctions in schizophrenia, but their dynamic consequences remain unclear. This study reports electrophysiological evaluation of medicated schizophrenic patients during performance of the Wisconsin Card Sorting Test. Using event-related potentials (ERPs), averaged after passing through several band pass filters, and source analysis with variable-resolution brain electrical tomography, cerebral sources were visualized at every latency point of the evoked potential. ERPs which differed from the control group were elicited principally in frontal, central, and parietal regions, within the delta and theta frequency ranges. Significant differences emerged at three different latencies (S1, S2, S3) in frontal/midline areas and at the anterior temporal electrode site T3 for slow potentials. The left occipitoparietal region showed significant differences within the alpha and beta 2 ranges, respectively. Medial fronto-orbital area and anterior cingulate cortex contributed to the development of the frontal ERPs and the lateral inferior frontal area to the temporal (T(3)) evoked-potential, while the precuneus/medial region generated the posterior activity recorded on the scalp. The significant intervals S1 and S3 were synchronous between the medial frontal and lateral inferior frontal region, while in the S2 interval the medial frontal areas were parallel with the precuneus/medial occipitotemporal region. A simultaneous functional imbalance between frontal subregions and posterior areas was uncovered. Here, we show for the first time an intermittent functional deficiency of specific brain areas during task-directed mentation in schizophrenia, which by its brevity is not accessible by neuroimaging methods measuring hemodynamic activity.