Abstract
Despite the increasing body of evidence supporting the hypothesis of schizophrenia as a disconnection syndrome, studies of resting-state EEG Source Functional Connectivity (EEG-SFC) in people affected by schizophrenia are sparse. The aim of the present study was to investigate resting-state EEG-SFC in 77 stable, medicated patients with schizophrenia (SCZ) compared to 78 healthy volunteers (HV). In order to study the effect of illness duration, SCZ were divided in those with a short duration of disease (SDD; n = 25) and those with a long duration of disease (LDD; n = 52). Resting-state EEG recordings in eyes closed condition were analyzed and lagged phase synchronization (LPS) indices were calculated for each ROI pair in the source-space EEG data. In delta and theta bands, SCZ had greater EEG-SFC than HV; a higher theta band connectivity in frontal regions was observed in LDD compared with SDD. In the alpha band, SCZ showed lower frontal EEG-SFC compared with HV whereas no differences were found between LDD and SDD. In the beta1 band, SCZ had greater EEG-SFC compared with HVs and in the beta2 band, LDD presented lower frontal and parieto-temporal EEG-SFC compared with HV. In the gamma band, SDD had greater connectivity values compared with LDD and HV. This study suggests that resting state brain network connectivity is abnormally organized in schizophrenia, with different patterns for the different EEG frequency components and that EEG can be a powerful tool to further elucidate the complexity of such disordered connectivity.
Highlights
IntroductionDisordered brain connectivity at cortical level, generally defined as failure of effective functional integration within and between brain areas, has been proposed as a core deficit of schizophrenia
Disordered brain connectivity at cortical level, generally defined as failure of effective functional integration within and between brain areas, has been proposed as a core deficit of schizophrenia.EEG functional connectivity in schizophreniaThis conclusion is based on neuroimaging evidence on structural, functional, and effective brain connectivity (Friston, 1998; Ribolsi et al, 2009; Schmitt et al, 2011)
In the beta1 band, the SCZ group presented greater EEG Source Functional Connectivity (EEG-SFC) compared with healthy volunteers (HV), and in short duration of disease (SDD) compared with long duration of disease (LDD) who had the lowest EEG-SFC
Summary
Disordered brain connectivity at cortical level, generally defined as failure of effective functional integration within and between brain areas, has been proposed as a core deficit of schizophrenia. This conclusion is based on neuroimaging evidence on structural, functional, and effective brain connectivity (Friston, 1998; Ribolsi et al, 2009; Schmitt et al, 2011). Transcranial magnetic stimulation (see for review Rogasch et al, 2014) and transcranial direct current stimulation (Hasan et al, 2013; Ribolsi et al, 2013) studies have identified altered inhibitory/excitatory properties of brain networks and of interhemispheric connectivity in schizophrenia. Confirmation of the central role of disordered connectivity has emerged from animal models of schizophrenia (Dickerson et al, 2010; Gruber et al, 2010)
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