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, 1 (1), 48-56

Differences in White Matter Reflect Atypical Developmental Trajectory in Autism: A Tract-based Spatial Statistics Study


Differences in White Matter Reflect Atypical Developmental Trajectory in Autism: A Tract-based Spatial Statistics Study

Reyhaneh Bakhtiari et al. Neuroimage Clin.


Autism is a neurodevelopmental disorder in which white matter (WM) maturation is affected. We assessed WM integrity in 16 adolescents and 14 adults with high-functioning autism spectrum disorder (ASD) and in matched neurotypical controls (NT) using diffusion weighted imaging and Tract-based Spatial Statistics. Decreased fractional anisotropy (FA) was observed in adolescents with ASD in tracts involved in emotional face processing, language, and executive functioning, including the inferior fronto-occipital fasciculus and the inferior and superior longitudinal fasciculi. Remarkably, no differences in FA were observed between ASD and NT adults. We evaluated the effect of age on WM development across the entire age range. Positive correlations between FA values and age were observed in the right inferior fronto-occipital fasciculus, the left superior longitudinal fasciculus, the corpus callosum, and the cortical spinal tract of ASD participants, but not in NT participants. Our data underscore the dynamic nature of brain development in ASD, showing the presence of an atypical process of WM maturation, that appears to normalize over time and could be at the basis of behavioral improvements often observed in high-functioning autism.

Keywords: ADI-R, Autism Diagnostic Interview-Revised; ADOS, Autism Diagnostic Observation Schedule; AQ, Autism Quotient; ASD, Autism Spectrum Disorders; ATR, anterior thalamic radiations; Autism spectrum disorder; Brain connectivity; Brain development; Brain maturation; CC, corpus callosum; CT, corticospinal tract; DTI, Diffusion Tensor Imaging; DTT, Diffusion Tensor Tractography; Diffusion Tensor Imaging; EF, executive functions; FA, fractional anisotropy; Fractional anisotropy; IFOF, inferior froto-occipital fasciculus; ILF, inferior longitudinal fasciculus; NT, neurotypical; PIQ, Performance Intelligence Quotient; SLF, superior longitudinal fasciculus; TBSS, Tract-based Spatial Statistics; TE, echo time; TFCE, Threshold-free Cluster Enhancement; TR, repetition time; UNC, uncinate fasciculus; VBM, Voxel-Based Morphometry; VBS, Voxel based Statistics of FA Images (VBM-like); WM, white matter.


Fig. 1
Fig. 1
Coronal (panel a), horizontal (panels b,c) and sagittal (panels d,e,f) sections showing areas of significantly decreased FA (p < 0.05, corrected) in ASD adolescents compared with age-matched controls, displayed on the MNI template brain. There are no regions where FA is significantly higher in the ASD group. Regions of decreased FA in ASD are highlighted on the mean FA skeleton (green) in colored voxels (scale ranging from blue to light blue). For visualization purposes, the stats images are ‘thickened’ with tbss_fill. MNI coordinates of each panel are as follows: a: y = 106; b: z = 96 c: z = 86; d: x = 123; e: x = 64; and f: x = 81. CT: cortico-spinal tract; BCC: body of corpus callosum; ILF: inferior longitudinal fasciculus; SLF: superior longitudinal fasciculus; SplCC: splenium of corpus callosum; Fm: forceps minor; FM: forceps major; IFOF: inferior fronto-occipital fasciculus; UNC: uncinate; CINh: cingulum, hippocampal region; CINc: cingulum, cingulate region; CC: corpus callosum.
Fig. 2
Fig. 2
Correlations between age and FA in ASD and NT in the body of CC and the SLF. Blue squares and line represent values for ASD, red circles and line represent value for NT (CON). Left panel: SLF, ASD: r = 0.41, p = 0.03; NT: r = 0.02, p = ns. Right panel: body of CC, ASD: r = 0.38, p = 0.04; NT: r = − 0.04, p = ns.

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