Left-hemispheric microstructural abnormalities in children with high-functioning autism spectrum disorder

Abstract

Current theories of the neurobiological basis of autism spectrum disorder (ASD) posit an altered pattern of connectivity in large-scale brain networks. Here we used diffusion tensor imaging to investigate the microstructural properties of the white matter (WM) that mediates interregional connectivity in 36 high-functioning children with ASD (HF-ASD) as compared with 37 controls. By employing an atlas-based analysis using large deformation diffeometric morphic mapping registration, a widespread but left-lateralized pattern of abnormalities was revealed. The mean diffusivity (MD) of water in the WM of HF-ASD children was significantly elevated throughout the left hemisphere, particularly in the outer-zone cortical WM. Across diagnostic groups, there was a significant effect of age on left-hemisphere MD, with a similar reduction in MD during childhood in both typically developing and HF-ASD children. The increased MD in children with HF-ASD suggests hypomyelination and may reflect increased short-range cortico-cortical connections subsequent to early WM overgrowth. These findings also highlight left-hemispheric connectivity as relevant to the pathophysiology of ASD and indicate that the spatial distribution of microstructural abnormalities in HF-ASD is widespread and left-lateralized. This altered left-hemispheric connectivity may contribute to deficits in communication and praxis observed in ASD.

Keywords: diffusion tensor imaging (DTI); laterality; neuroimaging; white matter.

Figure 1

Regions where Mean Diffusivity is elevated in HF-ASD. The colored regions correspond to the atlas regions that survive the initial p<0.05 threshold test.

Figure 2

Scatterplots of group difference in Mean Diffusivity (MD). Left hemisphere cortical MD is elevated in HF-ASD (p=0.002), as is left hemisphere core WM (p=0.0185).