Abstract
Atypical cortical organization and reduced integrity of the gray–white matter boundary have been reported by postmortem studies in individuals with autism spectrum disorder (ASD). However, there are no in vivo studies that examine these particular features of cortical organization in ASD. Hence, we used structural magnetic resonance imaging to examine differences in tissue contrast between gray and white matter in 98 adults with ASD and 98 typically developing controls, to test the hypothesis that individuals with ASD have significantly reduced tissue contrast. More specifically, we examined contrast as a percentage between gray and white matter tissue signal intensities (GWPC) sampled at the gray–white matter boundary, and across different cortical layers. We found that individuals with ASD had significantly reduced GWPC in several clusters throughout the cortex (cluster, P < 0.05). As expected, these reductions were greatest when tissue intensities were sampled close to gray–white matter interface, which indicates a less distinct gray–white matter boundary in ASD. Our in vivo findings of reduced GWPC in ASD are therefore consistent with prior postmortem findings of a less well-defined gray–white matter boundary in ASD. Taken together, these results indicate that GWPC might be utilized as an in vivo proxy measure of atypical cortical microstructural organization in future studies.
Highlights
Autism spectrum disorder (ASD) is a lifelong neurodevelopmental condition characterized by impaired social communication, deficits in social reciprocity, and repetitive and stereotypic behaviors and interests (Wing 1997)
We found that individuals with autism spectrum disorder (ASD) had a significantly decreased Gray-to-White Matter Percent Contrast (GWPC) in several clusters across the cortex, which is consistent with a reduced tissue contrast between gray and white matter (Fig. 2)
In accordance with our hypothesis, the reductions in GWPC were most extensive when Gray-matter tissue intensities (GMI) was sampled at gray–white matter boundary, and gradually decreased in both statistical effect and spatial extent with increasing projection fractions into cortex and away from the gray–white matter boundary
Summary
Autism spectrum disorder (ASD) is a lifelong neurodevelopmental condition characterized by impaired social communication, deficits in social reciprocity, and repetitive and stereotypic behaviors and interests (Wing 1997). These core symptoms typically manifest from early childhood, and are accompanied by developmental differences in brain anatomy and connectivity (for review, see Amaral et al 2008; Ecker et al 2015; Lange et al 2015). There is some evidence to suggest that the cortical differences accompanying ASD may result from atypical neuronal proliferation, migration, and maturation (Pinto et al 2014). To date no study has investigated differences in the integrity of the gray–white matter boundary in ASD in vivo across the whole brain
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