title: Traumatic brain injury impairs small-world topology.
abstract: OBJECTIVE
  We test the hypothesis that brain networks associated with cognitive function shift away from a "small-world" organization following traumatic brain injury (TBI).
  
  
  METHODS
  We investigated 20 TBI patients and 21 age-matched controls. Resting-state functional MRI was used to study functional connectivity. Graph theoretical analysis was then applied to partial correlation matrices derived from these data. The presence of white matter damage was quantified using diffusion tensor imaging.
  
  
  RESULTS
  Patients showed characteristic cognitive impairments as well as evidence of damage to white matter tracts. Compared to controls, the graph analysis showed reduced overall connectivity, longer average path lengths, and reduced network efficiency. A particular impact of TBI is seen on a major network hub, the posterior cingulate cortex. Taken together, these results confirm that a network critical to cognitive function shows a shift away from small-world characteristics.
  
  
  CONCLUSIONS
  We provide evidence that key brain networks involved in supporting cognitive function become less small-world in their organization after TBI. This is likely to be the result of diffuse white matter damage, and may be an important factor in producing cognitive impairment after TBI.
authors.affiliation: Computational, Cognitive and Clinical Neuroimaging Laboratory, The Division of Experimental Medicine, Imperial College London, Hammersmith Hospital Campus, London, UK.
authors.forename: Anand S
authors.initials: AS
authors.lastname: Pandit
authors.forename: Paul
authors.initials: P
authors.lastname: Expert
authors.forename: Renaud
authors.initials: R
authors.lastname: Lambiotte
authors.forename: Valerie
authors.initials: V
authors.lastname: Bonnelle
authors.forename: Robert
authors.initials: R
authors.lastname: Leech
authors.forename: Federico E
authors.initials: FE
authors.lastname: Turkheimer
authors.forename: David J
authors.initials: DJ
authors.lastname: Sharp
mesh_terms: D000293:Adolescent; D000328:Adult; D001930:Brain Injuries / Q000175:diagnosis* / Q000473:pathology / Q000523:psychology; D001931:Brain Mapping / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000473:pathology*; D009483:Neuropsychological Tests; D055815:Young Adult