title: Aberrant "default mode" functional connectivity in schizophrenia.
abstract: OBJECTIVE
  The "default mode" has been defined as a baseline condition of brain function and is of interest because its component brain regions are believed to be abnormal in schizophrenia. It was hypothesized that the default mode network would show abnormal activation and connectivity in patients with schizophrenia.
  
  
  METHODS
  Patients with schizophrenia (N=21) and healthy comparison subjects (N=22) performed an auditory oddball task during functional magnetic resonance imaging (fMRI). Independent component analysis was used to identify the default mode component. Differences in the spatial and temporal aspects of the default mode network were examined in patients versus comparison subjects.
  
  
  RESULTS
  Healthy comparison subjects and patients had significant spatial differences in the default mode network, most notably in the frontal, anterior cingulate, and parahippocampal gyri. In addition, activity in patients in the medial frontal, temporal, and cingulate gyri correlated with severity of positive symptoms. The patients also showed significantly higher frequency fluctuations in the temporal evolution of the default mode.
  
  
  CONCLUSIONS
  Schizophrenia is associated with altered temporal frequency and spatial location of the default mode network. The authors hypothesized that this network may be under- or overmodulated by key regions, including the anterior and posterior cingulate cortex. In addition, the altered temporal fluctuations in patients may result from a change in the connectivity of these regions with other brain networks.
authors.affiliation: Trinity College, Hartford, CT, USA.
authors.forename: Abigail G
authors.initials: AG
authors.lastname: Garrity
authors.forename: Godfrey D
authors.initials: GD
authors.lastname: Pearlson
authors.forename: Kristen
authors.initials: K
authors.lastname: McKiernan
authors.forename: Dan
authors.initials: D
authors.lastname: Lloyd
authors.forename: Kent A
authors.initials: KA
authors.lastname: Kiehl
authors.forename: Vince D
authors.initials: VD
authors.lastname: Calhoun
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001307:Auditory Perception / Q000502:physiology; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006179:Gyrus Cinguli / Q000503:physiopathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D009434:Neural Pathways / Q000503:physiopathology*; D020534:Parahippocampal Gyrus / Q000502:physiology; D010470:Perceptual Masking / Q000502:physiology; D025341:Principal Component Analysis; D012559:Schizophrenia / Q000175:diagnosis / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D012720:Severity of Illness Index