Cortical folding abnormalities in autism revealed by surface-based morphometry.

We tested for cortical shape abnormalities using surface-based morphometry across a range of autism spectrum disorders (7.5-18 years of age). We generated sulcal depth maps from structural magnetic resonance imaging data and compared typically developing controls to three autism spectrum disorder subgroups: low-functioning autism, high-functioning autism, and Asperger's syndrome. The low-functioning autism group had a prominent shape abnormality centered on the pars opercularis of the inferior frontal gyrus that was associated with a sulcal depth difference in the anterior insula and frontal operculum. The high-functioning autism group had bilateral shape abnormalities similar to the low-functioning group, but smaller in size and centered more posteriorly, in and near the parietal operculum and ventral postcentral gyrus. Individuals with Asperger's syndrome had bilateral abnormalities in the intraparietal sulcus that correlated with age, intelligence quotient, and Autism Diagnostic Interview-Revised social and repetitive behavior scores. Because of evidence suggesting age-related differences in the developmental time course of neural alterations in autism, separate analyses on children (7.5-12.5 years of age) and adolescents (12.75-18 years of age) were also carried out. All of the cortical shape abnormalities identified across all ages were more pronounced in the children. These findings are consistent with evidence of an altered trajectory of early brain development in autism, and they identify several regions that may have abnormal patterns of connectivity in individuals with autism.