The shape of the social brain in autism. a source-based morphometric study

Autism is a neurodevelopmental disorder that mainly affects social interaction and communication. Evidence coming from behavioral and functional MRI studies supports the hypothesis that autism may be caused by dysfunctional mechanisms involving social brain structures. However, the investigation of anatomical abnormalities in autistic brains led to inconsistent results. Our hypothesis is that brain regions involved in autism and discovered by previous studies may be part of an anatomical social network that shows aberrant pattern in autism. We analyzed 32 structural MRI of young men affected by autistic disorder (AD) and 50 of controls, matched for sex, age and handedness. IQ scores were also monitored to avoid confoundings. A multivariate method that uses Independent Component Analysis known as Source-Based Morphometry was applied for the first time to detect maximally independent networks of gray matter in both groups. Group comparison revealed a gray-matter network that is less expressed in AD rather than controls. This network includes broad temporal regions involved in social cognition and high-level visual processing, but also motor and executive areas of the frontal lobe. Abnormalities were also detected in the middle occipital lobe and in the cerebellar tonsil. Notably, we found that the level of expression of this network correlates with the social deficits displayed by individuals suffering from autism. We argue that these findings support the hypothesis of atypical processing of social-relevant information as a main factor in autistic disorder.