Phylogenetic based variation in autism

Abstract

Variation in brains across mammals and within humans is characterized by inter‐correlations in brain region volumes, distinct allometric scaling for each brain region and the relative independence in limbic structure volumes from the rest of the brain. Autism is a disorder characterized by impaired communication and deficits in social reciprocity. Studies have implicated the limbic system and cerebellum in autism but these studies have yielded contradictory results. We hypothesized that autism is characterized by abnormalities in the variation in brain region volumes that is observed within and across species. We used MRI scans from the ABIDE and OASIS databases to estimate brain volumes and 9 of its subdivisions (e.g., isocortex) in 41 autistic and 69 control individuals ranging between 16 to 29 years of age. Variation in autistic brains resembles but also differs from the individual variation observed in controls. The slopes of each brain region regressed against the brainstem in autistic and control individuals are similar. Limbic structures scale with relative independence from the rest of the brain in autistic and control individuals. However, the cerebellum of individuals with autism varies relatively independently of other brain regions, exhibiting very larger or small cerebella for a given brain size. Thus, our data suggest that the pattern of variation in the cerebellum is abnormal in autism.Grant Funding Source: N/A