Toddlers with autism appear more likely to have an enlarged amygdala, a brain area associated with numerous functions, including the processing of faces and emotion, according to a report in the journal Archives of General Psychiatry. In addition, this brain abnormality appears to be associated with the ability to share attention with others, a fundamental ability thought to predict later social and language function in children with autism.

 

The researchers at the University of North Carolina at Chapel Hill, who conducted a magnetic resonance imaging study involving 50 autistic children and 33 control children, say converging evidence from magnetic resonance imaging, head circumference, and postmortem studies suggests that brain volume enlargement is a characteristic feature of autism, with its onset most likely occurring in the latter part of the first year of life. Based both on its function and studies of changes in its structure, the amygdala has been identified as a brain area potentially associated with autism.

 

Children participating in the study underwent brain scans along with testing of certain behavioral features of autism at ages 2 and 4. This included a measure of joint attention, which involves following another person's gaze to initiate a shared experience. Compared to control children, those children with autism were more likely to have amygdala enlargement both at age 2 and age 4.

 

Among children with autism, amygdala volume was associated with an increase in joint attention ability at age 4. The researchers say this suggests that alterations to this brain structure may be associated with a core deficit of autism. “The amygdala plays a critical role in early-stage processing of facial expression and in alerting cortical areas to the emotional significance of an event,” the researchers say, “and Amygdala disturbances disrupt the appropriate assignment of emotional significance to faces and social interaction.”