title: Microstructural abnormalities of short-distance white matter tracts in autism spectrum disorder.
abstract: Recent functional connectivity magnetic resonance imaging and diffusion tensor imaging (DTI) studies have suggested atypical functional connectivity and reduced integrity of long-distance white matter fibers in autism spectrum disorder (ASD). However, evidence for short-distance white matter fibers is still limited, despite some speculation of potential sparing of local connectivity in ASD. Short-distance U-fibers are an important component of neural networks and are thought to play a crucial role in cognitive function. In the present study, we applied tract-based spatial statistics to derive short- and long-distance white matter tracts in frontal, parietal, and temporal lobes in both hemispheres. DTI data were acquired from 26 children with ASD and 24 typically developing (TD) children. A mean fractional anisotropy (FA) image was created and thinned to represent centers of all common tracts. Evidence of compromised short-distance tracts for the ASD group was found in frontal lobe (reduced FA, increased mean diffusivity [MD] and radial diffusivity) as well as in temporal and parietal lobes (increased MD and radial diffusivity). Significant positive correlations between age and FA and negative correlations between age and MD and radial diffusivity were also found for short-distance tracts in each lobe in the TD, but not the ASD group. These results suggest white matter compromise in short-distance tracts in ASD. Absence of typical age-related correlations with DTI indices may reflect altered maturation of short-distance tracts in ASD. Our results are inconsistent with a notion of selective sparing of short-distance connectivity in ASD.
authors.affiliation: Brain Development Imaging Lab, Department of Psychology, San Diego State University, 6363 Alvarado Ct, Suite 225E, San Diego, CA, USA.
authors.forename: Dinesh K
authors.initials: DK
authors.lastname: Shukla
authors.affiliation: Brain Development Imaging Lab, Department of Psychology, San Diego State University, 6363 Alvarado Ct, Suite 225E, San Diego, CA, USA; Joint Doctoral Program in Language and Communicative Disorders, San Diego State University / University of California, San Diego, CA, USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: Keehn
authors.affiliation: Brain Development Imaging Lab, Department of Psychology, San Diego State University, 6363 Alvarado Ct, Suite 225E, San Diego, CA, USA.
authors.forename: Daren M
authors.initials: DM
authors.lastname: Smylie
authors.affiliation: Brain Development Imaging Lab, Department of Psychology, San Diego State University, 6363 Alvarado Ct, Suite 225E, San Diego, CA, USA. Electronic address: amueller@sciences.sdsu.edu.
authors.forename: Ralph-Axel
authors.initials: RA
authors.lastname: Müller
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D001921:Brain / Q000473:pathology*; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009434:Neural Pathways / Q000473:pathology; D013223:Statistics as Topic