P37. Decreased functional electrophysiological cortical connectivity in first episode medication-naive schizophrenics: A three-center study

Abstract

Aims Abnormality of thought and emotion in schizophrenic patients is widely hypothesized to be caused by functional dissociation between brain processes. Analyses of the typically small groups of schizophrenic patients yielded different neurophysiological findings, because small patient groups are likely to comprise different schizophrenia subtypes. We wanted to see whether there are identical deteriorated cortical functional EEG connectivities in different patient groups. Methods Multichannel no-task resting eyes-closed EEG from three small groups of acutely ill, first episode productive schizophrenic patients before start of medication (from three centers: Bern N = 9; Osaka N = 9; Berlin N = 12) and their controls was analyzed. Using LORETA (low resolution brain electromagnetic tomography), we computed intracortical source model-based lagged functional connectivity (not biased by volume conduction effects) between 19 cortical regions of interest (ROIs). The connectivities were compared between controls and patients of each group. The results across groups were combined using conjunction analysis. Results Six aberrant cortical functional connectivities were identical in the three patient groups as determined by conjunction analysis. Four of these occurred in the facilitating EEG alpha 1 frequency band; they were decreased in the patients. Another two of these occurred in the inhibiting EEG delta frequency band; they were increased in the patients. Thus, all six reduced the functional interactions between the concerned brain regions. The principal spatial orientation of the six aberrant cortical functional connectivities was sagittal; five of them involved both hemispheres. Conclusions The study shows that, common across schizophrenia subtypes in the three patient groups, a core set of functional connections between the preprocessing functions in posterior brain areas and the evaluation and behavior control functions in anterior brain areas is compromised. The results also support the concept of functional dissociation in schizophrenia.