title: Constrained spherical deconvolution-based tractography and tract-based spatial statistics show abnormal microstructural organization in Asperger syndrome.
abstract: BACKGROUND
  The aim of this study was to investigate potential differences in neural structure in individuals with Asperger syndrome (AS), high-functioning individuals with autism spectrum disorder (ASD). The main symptoms of AS are severe impairments in social interactions and restricted or repetitive patterns of behaviors, interests or activities.
  
  
  METHODS
  Diffusion weighted magnetic resonance imaging data were acquired for 14 adult males with AS and 19 age, sex and IQ-matched controls. Voxelwise group differences in fractional anisotropy (FA) were studied with tract-based spatial statistics (TBSS). Based on the results of TBSS, a tract-level comparison was performed with constrained spherical deconvolution (CSD)-based tractography, which is able to detect complex (for example, crossing) fiber configurations. In addition, to investigate the relationship between the microstructural changes and the severity of symptoms, we looked for correlations between FA and the Autism Spectrum Quotient (AQ), Empathy Quotient and Systemizing Quotient.
  
  
  RESULTS
  TBSS revealed widely distributed local increases in FA bilaterally in individuals with AS, most prominent in the temporal part of the superior longitudinal fasciculus, corticospinal tract, splenium of corpus callosum, anterior thalamic radiation, inferior fronto-occipital fasciculus (IFO), posterior thalamic radiation, uncinate fasciculus and inferior longitudinal fasciculus (ILF). CSD-based tractography also showed increases in the FA in multiple tracts. However, only the difference in the left ILF was significant after a Bonferroni correction. These results were not explained by the complexity of microstructural organization, measured using the planar diffusion coefficient. In addition, we found a correlation between AQ and FA in the right IFO in the whole group.
  
  
  CONCLUSIONS
  Our results suggest that there are local and tract-level abnormalities in white matter (WM) microstructure in our homogenous and carefully characterized group of adults with AS, most prominent in the left ILF.
authors: Brain and Mind Laboratory, Department of Biomedical Engineering and Computational Science, Aalto University, Rakentajanaukio 2 C, FI-02150 Espoo, Finland.
authors: Ulrika
authors: U
authors: Roine
authors: Brain and Mind Laboratory, Department of Biomedical Engineering and Computational Science, Aalto University, Rakentajanaukio 2 C, FI-02150 Espoo, Finland.
authors: Juha
authors: J
authors: Salmi
authors: iMinds-Vision Lab, Department of Physics, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Antwerp Belgium.
authors: Timo
authors: T
authors: Roine
authors: Neuropsychiatric Rehabilitation and Medical Centre Neuromental, Kaupintie 11 A, FI-00440 Helsinki, Finland.
authors: Taina Nieminen-von
authors: TN
authors: Wendt
authors: Department of Psychiatry, Clinic for Neuropsychiatry, Helsinki University Central Hospital, Tukholmankatu 8 F, FI-00290 Helsinki, Finland ; Finnish Institute of Occupational Health, Topeliuksenkatu 41, FI-00290 Helsinki, Finland.
authors: Sami
authors: S
authors: Leppämäki
authors: Department of Psychiatry, Clinic for Neuropsychiatry, Helsinki University Central Hospital, Tukholmankatu 8 F, FI-00290 Helsinki, Finland.
authors: Pertti
authors: P
authors: Rintahaka
authors: Department of Psychiatry, Clinic for Neuropsychiatry, Helsinki University Central Hospital, Tukholmankatu 8 F, FI-00290 Helsinki, Finland.
authors: Pekka
authors: P
authors: Tani
authors: Image Sciences Institute, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
authors: Alexander
authors: A
authors: Leemans
authors: Brain and Mind Laboratory, Department of Biomedical Engineering and Computational Science, Aalto University, Rakentajanaukio 2 C, FI-02150 Espoo, Finland ; Advanced Magnetic Imaging Centre, Aalto University, Otakaari 5, FI-02150 Espoo, Finland.
authors: Mikko
authors: M
authors: Sams
keywords: autism spectrum disorder; diffusion magnetic resonance imaging; fractional anisotropy; inferior longitudinal fasciculus; white matter tract