Amygdala Size Associated with Symptoms of Autism

Children with autism seem to be more likely to have an enlarged amygdala, which regulates the ability to process faces and emotions, a recent study has found.

Matthew W. Mosconi, Ph.D., and colleagues at the University of North Carolina at Chapel Hill also found that autistic children with an enlarged amygdala have a decreased ability to share attention with other children, which is thought to impact later development of social skills and language in children with the disorder.

Fifty autistic children and 33 controls — one-third of whom were developmentally delayed, the other two-thirds who were typically developing, according to an abstract of the journal article that was published in the May 2009 issue of Archives of General Psychiatry — took part in the MRI study, which examined their brains and tested other behavioral features of autism, including measures of joint attention — “following another person's gaze to initiate a shared experience” at ages two and four."

"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," the authors said.

Children with autism were more likely to have enlarged amygdalas at the times of both scans when compared to the control children. In addition, the size of the amygdala was associated with an increase in the ability of joint attention at age four.

Because of the association between “amygdala volume and joint attention ability,” as it is described in the journal abstract, it is suggested by the researchers “that alternations to this structure may be linked to 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 authors said. "Amygdala disturbances early in development, therefore, disrupt the appropriate assignment of emotional significance to faces and social interaction."

As part of the researchers’ follow up with the participants, they will be able to determine if growth of the amygdala continues at one rate, experiences a period of accelerate growth, or decreases for both groups of children beyond age four.