title: White-matter relaxation time and myelin water fraction differences in young adults with autism.
abstract: BACKGROUND
  Increasing evidence suggests that autism is associated with abnormal white-matter (WM) anatomy and impaired brain 'connectivity'. While myelin plays a critical role in synchronized brain communication, its aetiological role in autistic symptoms has only been indirectly addressed by WM volumetric, relaxometry and diffusion tensor imaging studies. A potentially more specific measure of myelin content, termed myelin water fraction (MWF), could provide improved sensitivity to myelin alteration in autism.
  
  
  METHODS
  We performed a cross-sectional imaging study that compared 14 individuals with autism and 14 age- and IQ-matched controls. T 1 relaxation times (T 1), T 2 relaxation times (T 2) and MWF values were compared between autistic subjects, diagnosed using the Autism Diagnostic Interview - Revised (ADI-R), with current symptoms assessed using the Autism Diagnostic Observation Schedule (ADOS) and typical healthy controls. Correlations between T 1, T 2 and MWF values with clinical measures [ADI-R, ADOS, and the Autism Quotient (AQ)] were also assessed.
  
  
  RESULTS
  Individuals with autism showed widespread WM T 1 and MWF differences compared to typical controls. Within autistic individuals, worse current social interaction skill as measured by the ADOS was related to reduced MWF although not T 1. No significant differences or correlations with symptoms were observed with respect to T 2.
  
  
  CONCLUSIONS
  Autistic individuals have significantly lower global MWF and higher T 1, suggesting widespread alteration in tissue microstructure and biochemistry. Areas of difference, including thalamic projections, cerebellum and cingulum, have previously been implicated in the disorder; however, this is the first study to specifically indicate myelin alteration in these regions.
authors.affiliation: Advanced Baby Imaging Laboratory,School of Engineering, Brown University,Providence, RI,USA.
authors.forename: S C L
authors.initials: SC
authors.lastname: Deoni
authors.affiliation: Department of Forensic and Neurodevelopmental Sciences,Institute of Psychiatry, King's College London,London,UK.
authors.forename: J R
authors.initials: JR
authors.lastname: Zinkstok
authors.affiliation: Department of Forensic and Neurodevelopmental Sciences,Institute of Psychiatry, King's College London,London,UK.
authors.forename: E
authors.initials: E
authors.lastname: Daly
authors.affiliation: Department of Forensic and Neurodevelopmental Sciences,Institute of Psychiatry, King's College London,London,UK.
authors.forename: C
authors.initials: C
authors.lastname: Ecker
authors.affiliation: Department of Neuroimaging,Institute of Psychiatry, King's College London,London,UK.
authors.forename: S C R
authors.initials: SC
authors.lastname: Williams
authors.affiliation: Department of Forensic and Neurodevelopmental Sciences,Institute of Psychiatry, King's College London,London,UK.
authors.forename: D G M
authors.initials: DG
authors.lastname: Murphy
mesh_terms: D000328:Adult; D001321:Autistic Disorder / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009186:Myelin Sheath / Q000737:chemistry / Q000473:pathology*; D066127:White Matter / Q000737:chemistry / Q000473:pathology*; D055815:Young Adult
keywords: white matter