Study links change in brain's emotional center to autism

MILWAUKEE, Wis. — In a new finding, University of Wisconsin-Madison researchers have documented changes in the brain's emotional center that may explain the social impairment seen in children with autism.

And in a separate French study, scientists identified a gene that may explain why some people develop autism.

The UW authors found that males with autism who spent the least time looking at a person's eyes in photographs had a much smaller amygdala — the almond-shaped danger-detecting region of the brain — than males without autism.

In addition, males with a small amygdala also had difficulty distinguishing any face showing an emotion from those with neutral expressions, researchers say.

"This is a great first step," said Stephen Rao, a professor of neurology and director of the functional imaging research center at the Medical College of Wisconsin, who was not involved in the study.

"We pick up a lot of emotions from our ability to distinguish facial expressions, so that's why eye-tracking is good," he said.

Still, more studies that demonstrate the exclusivity of the amygdala need to be done before more conclusions are made, Rao said.

Autism, the most common condition in a group of developmental disorders known as autism spectrum disorders, is a serious brain disorder that begins in infancy and prevents children from developing normally.

Common signs, which can range from mild to severe, include impaired social interaction, problems with verbal and non-verbal communication, and unusual, repetitive, or severely limited activities and interests.

For the UW study, researchers analyzed data from 54 males, including 28 with autism spectrum disorders, who were ages 8 to 25. The participants were tested using magnetic resonance imaging and an eye-tracking device to record where they looked. This method allowed the authors to directly relate amygdala size with how much time the subjects spent looking at the eyes of pictured faces.

Participants in the autism group who had a small amygdala were significantly slower to identify happy, angry or sad facial expressions and spent the least amount of time looking at eyes on the photos. It took these males 40 percent longer than those with the large amygdala to recognize the emotional facial expressions, and those with the largest amygdala spent about four times longer looking at eyes than those with the smallest.