title: Shifted coupling of EEG driving frequencies and fMRI resting state networks in schizophrenia spectrum disorders.
abstract: BACKGROUND
  The cerebral resting state in schizophrenia is altered, as has been demonstrated separately by electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) resting state networks (RSNs). Previous simultaneous EEG/fMRI findings in healthy controls suggest that a consistent spatiotemporal coupling between neural oscillations (EEG frequency correlates) and RSN activity is necessary to organize cognitive processes optimally. We hypothesized that this coupling is disorganized in schizophrenia and related psychotic disorders, in particular regarding higher cognitive RSNs such as the default-mode (DMN) and left-working-memory network (LWMN).
  
  
  METHODS
  Resting state was investigated in eleven patients with a schizophrenia spectrum disorder (n = 11) and matched healthy controls (n = 11) using simultaneous EEG/fMRI. The temporal association of each RSN to topographic spectral changes in the EEG was assessed by creating Covariance Maps. Group differences within, and group similarities across frequencies were estimated for the Covariance Maps.
  
  
  RESULTS
  The coupling of EEG frequency bands to the DMN and the LWMN respectively, displayed significant similarities that were shifted towards lower EEG frequencies in patients compared to healthy controls.
  
  
  CONCLUSIONS
  By combining EEG and fMRI, each measuring different properties of the same pathophysiology, an aberrant relationship between EEG frequencies and altered RSNs was observed in patients. RSNs of patients were related to lower EEG frequencies, indicating functional alterations of the spatiotemporal coupling.
  
  
  CONCLUSIONS
  The finding of a deviant and shifted coupling between RSNs and related EEG frequencies in patients with a schizophrenia spectrum disorder is significant, as it might indicate how failures in the processing of internal and external stimuli, as commonly seen during this symptomatology (i.e. thought disorders, hallucinations), arise.
authors.affiliation: Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, University of Bern, Bern, Switzerland.
authors.forename: Nadja
authors.initials: N
authors.lastname: Razavi
authors.forename: Kay
authors.initials: K
authors.lastname: Jann
authors.forename: Thomas
authors.initials: T
authors.lastname: Koenig
authors.forename: Mara
authors.initials: M
authors.lastname: Kottlow
authors.forename: Martinus
authors.initials: M
authors.lastname: Hauf
authors.forename: Werner
authors.initials: W
authors.lastname: Strik
authors.forename: Thomas
authors.initials: T
authors.lastname: Dierks
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology* / Q000503:physiopathology*; D001931:Brain Mapping; D016022:Case-Control Studies; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D012559:Schizophrenia / Q000175:diagnosis*; D055815:Young Adult