title: Failure to deactivate the default mode network indicates a possible endophenotype of autism.
abstract: BACKGROUND
  Reduced activity during cognitively demanding tasks has been reported in the default mode network in typically developing controls and individuals with autism. However, no study has investigated the default mode network (DMN) in first-degree relatives of those with autism (such as siblings) and it is not known whether atypical activation of the DMN is specific to autism or whether it is also present in unaffected relatives. Here we use functional magnetic resonance imaging to investigate the pattern of task-related deactivation during completion of a visual search task, the Embedded Figures Task, in teenagers with autism, their unaffected siblings and typically developing controls.
  
  
  RESULTS
  We identified striking reductions in deactivation during the Embedded Figures Task in unaffected siblings compared to controls in brain regions corresponding to the default mode network. Adolescents with autism and their unaffected siblings similarly failed to deactivate regions, including posterior cingulate and bilateral inferior parietal cortex.
  
  
  CONCLUSIONS
  This suggests that a failure to deactivate these regions is a functional endophenotype of autism, related to familial risk for the condition shared between individuals with autism and their siblings.
authors.affiliation: Department of Psychiatry, Autism Research Centre, University of Cambridge, Douglas House, 18b Trumpington Road, Cambridge, CB2 8AH, UK. mds1003@cam.ac.uk.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Spencer
authors.forename: Lindsay R
authors.initials: LR
authors.lastname: Chura
authors.forename: Rosemary J
authors.initials: RJ
authors.lastname: Holt
authors.forename: John
authors.initials: J
authors.lastname: Suckling
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Calder
authors.forename: Edward T
authors.initials: ET
authors.lastname: Bullmore
authors.forename: Simon
authors.initials: S
authors.lastname: Baron-Cohen