title: Increased Resting-State Gamma-Band Connectivity in First-Episode Schizophrenia.
abstract: BACKGROUND
  Schizophrenia has long been suggested to represent a disorder with prominent neural dysconnectivity. Gamma-band oscillations are highly relevant in this context, due both to their proposed involvement in neuronal synchronization and to their association with neurotransmitter systems relevant for schizophrenia. Several task-related studies have confirmed reduced power and synchronization of gamma-band oscillations in schizophrenia, but it has been suggested that these findings might not apply to the resting state. The present study aimed to investigate resting-state gamma-band connectivity in patients with schizophrenia.
  
  
  METHODS
  Sixty-four channel resting-state electroencephalography (eyes closed) was recorded in 22 patients with first-episode schizophrenia and 22 healthy controls matched for age and gender. Orthogonalized power envelope correlation was used as a measure of connectivity across 80 cortical regions at 40 Hz. Mean connectivity at each region was compared across groups using the nonparametric randomization approach. Additionally, the network-based statistic was applied to identify affected networks in patients.
  
  
  RESULTS
  Patients displayed increased mean functional gamma-band connectivity compared to controls in the left rolandic operculum. Network-based analyses indicated increased connectivity in patients within a strongly lateralized network consisting mainly of left inferior frontal/orbitofrontal, lateral and medial temporal, and inferior parietal areas. Within this network, gamma-band connectivity was higher in patients with low positive and disorganization symptom levels.
  
  
  CONCLUSIONS
  The present study provides a link between resting-state gamma-band connectivity and the core symptoms of schizophrenia. The observed findings are different than those reported by task-related studies, suggesting that resting-state studies might reveal new aspects in the pathophysiology of schizophrenia.
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; c.andreou@uke.de.
authors.forename: Christina
authors.initials: C
authors.lastname: Andreou
authors.affiliation: Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
authors.forename: Guido
authors.initials: G
authors.lastname: Nolte
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
authors.forename: Gregor
authors.initials: G
authors.lastname: Leicht
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
authors.forename: Nenad
authors.initials: N
authors.lastname: Polomac
authors.affiliation: Developmental Neurophysiology, Institute of Neuroanatomy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Ileana L
authors.initials: IL
authors.lastname: Hanganu-Opatz
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
authors.forename: Martin
authors.initials: M
authors.lastname: Lambert
authors.affiliation: Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
authors.forename: Andreas K
authors.initials: AK
authors.lastname: Engel
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
authors.forename: Christoph
authors.initials: C
authors.lastname: Mulert
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology*; D063132:Connectome; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D065818:Gamma Rhythm / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009415:Nerve Net / Q000503:physiopathology*; D012559:Schizophrenia / Q000503:physiopathology*; D055815:Young Adult
keywords: EEG; disorganization; functional connectivity; positive symptoms; power envelope correlation; psychosis