title: Static and dynamic characteristics of cerebral blood flow during the resting state in schizophrenia.
abstract: BACKGROUND
  The cerebral network that is active during rest and is deactivated during goal-oriented activity is called the default mode network (DMN). It appears to be involved in self-referential mental activity. Atypical functional connectivity in the DMN has been observed in schizophrenia. One hypothesis suggests that pathologically increased DMN connectivity in schizophrenia is linked with a main symptom of psychosis, namely, misattribution of thoughts.
  
  
  METHODS
  A resting-state pseudocontinuous arterial spin labeling (ASL) study was conducted to measure absolute cerebral blood flow (CBF) in 34 schizophrenia patients and 27 healthy controls. Using independent component analysis (ICA), the DMN was extracted from ASL data. Mean CBF and DMN connectivity were compared between groups using a 2-sample t test.
  
  
  RESULTS
  Schizophrenia patients showed decreased mean CBF in the frontal and temporal regions (P < .001). ICA demonstrated significantly increased DMN connectivity in the precuneus (x/y/z = -16/-64/38) in patients than in controls (P < .001). CBF was not elevated in the respective regions. DMN connectivity in the precuneus was significantly correlated with the Positive and Negative Syndrome Scale scores (P < .01).
  
  
  CONCLUSIONS
  In schizophrenia patients, the posterior hub--which is considered the strongest part of the DMN--showed increased DMN connectivity. We hypothesize that this increase hinders the deactivation of the DMN and, thus, the translation of cognitive processes from an internal to an external focus. This might explain symptoms related to defective self-monitoring, such as auditory verbal hallucinations or ego disturbances.
authors: Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, University of Bern, Bern, Switzerland; jochen.kindler@puk.unibe.ch.
authors: Jochen
authors: J
authors: Kindler
authors: Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, University of Bern, Bern, Switzerland; Laboratory of Functional MRI Technology, Ahmanson-Lovelace Brain Mapping Center, Department of Neurology, University of California Los Angeles, Los Angeles, CA;
authors: Kay
authors: K
authors: Jann
authors: Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, University of Bern, Bern, Switzerland;
authors: Philipp
authors: P
authors: Homan
authors: Support Center for Advanced Neuroimaging (SCAN), Institute for Diagnostic and Interventional Neuroradiology, Inselspital, University of Bern, Bern, Switzerland;
authors: Martinus
authors: M
authors: Hauf
authors: Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, University of Bern, Bern, Switzerland;
authors: Sebastian
authors: S
authors: Walther
authors: Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, University of Bern, Bern, Switzerland;
authors: Werner
authors: W
authors: Strik
authors: Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, University of Bern, Bern, Switzerland;
authors: Thomas
authors: T
authors: Dierks
authors: Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, University of Bern, Bern, Switzerland;
authors: Daniela
authors: D
authors: Hubl
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply*; D016022:Case-Control Studies; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D066128:Gray Matter / Q000098:blood supply*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging; D012559:Schizophrenia / Q000503:physiopathology*
keywords: arterial spin labeling; default mode network; functional connectivity; precuneus; psychosis