International Meeting for Autism Research (May 7 - 9, 2009): Microstructural Connectivity of the Arcuate Fasciculus in Autism

Thursday, May 7, 2009

Northwest Hall (Chicago Hilton)

11:00 AM

P. T. Fletcher , School of Computing, University of Utah, Salt Lake City, UT

R. Whitaker , School of Computing, University of Utah, Salt Lake City, UT

R. Tao , School of Computing, University of Utah, Salt Lake City, UT

M. DuBray , Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, UT

A. L. Alexander , Department of Medical Physics, Department of Psychiatry, Waisman Laboratory for Brain Imaging & Behavior, University of Wisconsin, Madison, WI

E. Bigler , Psychology & Neuroscience, Brigham Young University, Provo, UT

N. Lange , Departments of Psychiatry and Biostatistics, Harvard University, Belmont, MA

J. E. Lainhart , Psychiatry, Neuroscience, & The Brain Institute, University of Utah, Salt Lake City, UT

Background: Language impairment in autism spectrum disorder is universal and often severe. Imaging and postmortem studies have shown abnormalities in the gray matter structures involved in language. The white matter structure of the language networks in the autism brain is unknown.

Objectives: The goal of this study was to investigate the white matter microstructure of the arcuate fasciculus in the autism brain using diffusion tensor imaging (DTI).

Methods: The data were collected as part of an ongoing longitudinal MRI study on brain development in autism. High resolution DTI was acquired from a 3T MRI scanner and analyzed on 10 individuals with autism and 10 control subjects. The arcuate fasciculus was extracted from the images using a new automated volumetric DTI segmentation algorithm. Derived measures of microstructure (fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD)) were computed in the arcuate fasciculus and compared across groups. Lateralization scores between the left and right arcuate fasciculi were computed for each diffusion measurement.

Results: As a group, those with autism displayed a significant increase in MD (p = 0.0002), which was due to increases in both AD (p = 0.015) and RD (p = 0.009). While there was no significant difference in the mean FA between the groups, the variance of FA was significantly greater (p = 0.016) in the autism group. A comparison of lateralization showed a lateralization in controls (increased FA and decreased MD on the left side) that was absent in the autism group.

Conclusions: Our findings suggest abnormal white matter microstructure in the arcuate fasciculus in autism. Furthermore, these results indicate that lateralized language specialization of the arcuate fasciculus is impaired in autism.

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