Repository | Book | Chapter

"The disconnection hypothesis' in schizophrenia emphasizes that the core dysfunction of this disease corresponds to a global decrease of neuronal connectivity involving widespread neuronal networks, or in other words to an alteration of the functional connectivity of the brain. Synchronization of EEG activity at high oscillatory frequencies (20 –100 Hz) has been proposed to reflect the degree of functional connectivity. Using this approach, a growing number of studies have shown a decrease in neuronal synchrony in schizophrenics, which correlates with perceptual and cognitive deficits in these patients. However, if impaired brain synchronization is a general feature of the schizophrenic brain, then multiple methods to assess functional connectivity should be expected to find similar results. Nevertheless, other techniques, such as functional resonance magnetic imaging (fMRI), have failed to completely fulfill this prediction. While in some brain regions hemodynamic activity is inferior to that of control subjects, other areas evidence an increased activation relative to controls. Moreover, on measuring the covariances in fMRI signals a significant increase in neuronal connectivity is observed in some areas, concomitant with a decrease of connectivity in other areas. Considering these results, we suggest that localized excesses of connectivity could also be involved in the functional changes accompanying schizophrenia. Thus, a decreased functional connectivity could be part of a more general "aberrant connectivity" phenomenon, whose signature is a disbalanced connectivity, some regions displaying an decrease and others an excess of connectivity; the latter arising in part as a compensatory mechanism attempting to restore the damaged sensorimotor circuits.

DOI: 10.1007/978-3-540-70573-4_15

Full citation: