Abstract
BackgroundThe corpus callosum is the largest white matter structure in the brain, and it is the most consistently reported to be atypical in diffusion tensor imaging studies of autism spectrum disorder. In individuals with typical development, the corpus callosum is known to undergo a protracted development from childhood through young adulthood. However, no study has longitudinally examined the developmental trajectory of corpus callosum in autism past early childhood.MethodsThe present study used a cohort sequential design over 9 years to examine age-related changes of the corpus callosum in 100 males with autism and 56 age-matched males with typical development from early childhood (when autism can first be reliably diagnosed) to mid-adulthood (after development of the corpus callosum has been completed) (3 to 41 years of age).ResultsThe group with autism demonstrated a different developmental trajectory of white matter microstructure in the anterior corpus callosum’s (genu and body) fractional anisotropy, which suggests atypical brain maturation in these regions in autism. When analyses were broken down by age group, atypical developmental trajectories were present only in the youngest participants (10 years of age and younger). Significant main effects for group were found in terms of decreased fractional anisotropy across all three subregions of the corpus callosum (genu, body, and splenium) and increased mean diffusivity, radial diffusivity, and axial diffusivity in the posterior corpus callosum.ConclusionsThese longitudinal results suggest atypical early childhood development of the corpus callosum microstructure in autism that transitions into sustained group differences in adolescence and adulthood. This pattern of results provides longitudinal evidence consistent with a growing number of published studies and hypotheses regarding abnormal brain connectivity across the life span in autism.Electronic supplementary materialThe online version of this article (doi:10.1186/s13229-015-0001-8) contains supplementary material, which is available to authorized users.
Highlights
The corpus callosum is the largest white matter structure in the brain, and it is the most consistently reported to be atypical in diffusion tensor imaging studies of autism spectrum disorder
diffusion tensor imaging (DTI) is based upon a Gaussian model of water diffusion in tissue and provides a description of white matter microstructure through the tensor measures, including the fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD)
Its developmental trajectory during the first 10 years of life was in the opposite direction of typical development; FA decreased during childhood in the Autism spectrum disorder (ASD) group but increased as expected in TDC children
Summary
The corpus callosum is the largest white matter structure in the brain, and it is the most consistently reported to be atypical in diffusion tensor imaging studies of autism spectrum disorder. Because the corpus callosum is composed predominately of parallel myelinated axon bundles in primates [20], it is well suited for investigation using diffusion tensor imaging (DTI) [21] to examine the microstructural integrity of the corpus callosum in persons with ASD. DTI is based upon a Gaussian model of water diffusion in tissue and provides a description of white matter microstructure through the tensor measures, including the fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD). An FA close to zero represents isotropic diffusion with long eigenvectors, and an FA of one represents highly directional diffusion with maximal elongation of one eigenvector compared to the others
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