The role of the fusiform-amygdala system in the pathophysiology of autism.

CONTEXT Autism is a condition of unknown origin with well-documented impairments in social perception and cognition. OBJECTIVE To assess the relevance of the fusiform-amygdala system to the pathophysiology of autism spectrum conditions. DESIGN Cross-sectional case-control study. SETTING University hospital. PARTICIPANTS A total of 27 adults with autism spectrum conditions and 29 age-, sex-, and intelligence quotient-matched typically developed healthy controls. Patients were assessed according to DSM-IV criteria using the Autism Diagnostic Interview-Revised. INTERVENTIONS We applied an automated measurement to estimate fusiform gyrus cortical thickness and a manual tracing method to obtain amygdala volumes. We analyzed volumetric covariance among these brain regions and assessed the functional relevance of anatomical findings by analyzing correlations with emotional face-processing performance. MAIN OUTCOME MEASURES Fusiform gyrus cortical thickness, amygdala volume, emotional face processing. RESULTS We found a specific local increase in cortical thickness of the fusiform gyrus and associated impairments in face processing in individuals with autism. Anatomical covariance between amygdala volume and the increase in fusiform gyrus local thickness was significantly smaller in the group with autism spectrum conditions. CONCLUSIONS Our data provide the first anatomical evidence of an abnormal amygdala-fusiform system and its behavioral relevance to face-processing deficits in autism spectrum conditions. In light of recent evidence of the involvement of the fusiform gyrus and amygdala in social perception as well as the areas of social cognition and emotional awareness, all of which are relevant to autism, our findings might represent a core pathophysiological mechanism of autism.