Study: Brain is atypical in autistic boys
Saturday, August 21, 2004 (20:15:31)

Posted by sylvia

The Sacramento Bee 15/07/2004

By Dorsey Griffith

A new study by the UC Davis MIND Institute has found that two areas in the brain are larger in boys with autism than in boys who are developing normally.

The study, published in Wednesday's edition of the Journal of Neuroscience, represents the most comprehensive examination yet of brain volume in children with autism.

The findings, which confirm some earlier studies, do not explore what caused the brain abnormalities or when the growth began to go awry but will better direct future autism research, said David Amaral, the study's principal investigator and research director at the MIND Institute.

"It's beginning to point to the idea that in certain children with autism there is a defect that allows the brain to develop too quickly," he said. "This gives us a target to carry out fundamental neuroscience."

Autistic people generally have difficulty speaking, relating to others and responding appropriately to their environment. The disorder typically is diagnosed in early childhood; some parents report their children were developing normally before symptoms appeared.

In the new study, researchers at the MIND Institute and Stanford University analyzed magnetic resonance images of the brains of 98 boys, ages 7 to 18 years. The group included 46 with autism; 25 with Asperger syndrome, a disorder on the autism spectrum; and 27 developing normally. Among the boys with autism were 19 also diagnosed with mental retardation.

The scientists found that two areas of the brain responsible for memory and emotion were larger in children with autism, regardless of their intelligence.

Specifically, they studied the amygdala, a brain region involved with processing emotions, and the hippocampus, associated with memory. They found that in normally developing boys the amygdala increased in size by about 40 percent over time. In autistic boys, however, the amyg dala was up to 17 percent larger than in normal boys initially but didn't change over time. The scientists said none of the children had an enlarged brain overall.

Amaral suggests that the difference in amygdala size relates to an autistic child brain's inability to use environmental experiences to build appropriate brain circuits.

"You want to get to an end point that has normal circuitry," he said. "If things go too fast or too slow it is unlikely you will get to that normal endpoint."

The amygdala also was larger in children with Asperger syndrome but to a lesser degree and not statistically significant.

The study did not determine which autism symptoms might be related to an abnormally developing amygdala. Amaral said the amygdala appears to be involved in emotions such as fear, which is common in autism.

The study also found that children with autism have an enlarged hippocampus, the part of the brain responsible for a person's ability to remember episodes from their lives.

The MIND Institute will continue to analyze the MRI data and plans to launch a larger study.

Parents of autistic and normally developing children interested in participating can call the Institute at (916) 703-0320.