Autistic toddlers seem more likely to have a brain area linked with facial recognition and emotions, University of North Carolina researchers reported.
This brain abnormality, known as an enlarged amygdala, appears to be tied to the ability to share attention and experiences with others, said the report, which was published in the May issue of the Archives of General Psychiatry.
The study comes on the heels of a report published online last week in the journal Nature that found that the inheritance of abnormal mutations of two common genes can raise the risk for developing autism. “[This study] adds clarification to a potential fundamental brain mechanism underlying social deficits in autism. It provides potential insights into how this behavior develops,” said lead researcher Dr. Joseph Piven, a professor of psychiatry.
“We found enlargement of the amygdala in very young children with autism at 2 years of age, and followed up again at age 4. The enlargement was stable over the 2- to 4-year-old time interval,” he said.
The amygdala is a structure that has previously been implicated in social and emotional perception and in autism, Piven said. “We also found that this enlargement was related to something called joint attention, or the ability of a young child to take cues from an adult about where to look in the visual field, for example, at an object of interest,” he said.
This ability develops in a narrow window, between 9 and 15 months, and is thought to be a fundamental deficit in autistic individuals that predicts poor outcomes in social behavior and language, Piven explained.
For the study, Piven’s team conducted MRI scans of 50 autistic children and 33 children without the condition. The children had brain scans and testing of certain behavioral features of autism at 2 and 4. The researchers found autistic children were more likely to have an enlarged amygdala at 2 and 4.
However, the researchers did not find a relationship between amygdala size and other social behaviors at this age, such as social gestures or ritualistic/repetitive behavior, Piven said.