Nov. 8, 2011 -- New research highlights some potentially important differences in the brains of children with autism.
The small study found that boys with autism had an average of 67% more brain cells called neurons in the prefrontal cortex region of their brains, when compared with children who did not have autism.
Located in the front of the brain beneath the forehead, the prefrontal cortex is responsible for "higher order" functions such as problem solving, emotions, and complex thought. These are some of the processes that are impaired in autism.
Most of these neurons develop before birth, which would go against the theory that certain vaccines or other environmental influences encountered after birth may cause autism.
The findings are published in TheJournal of the American Medical Association.
"It's a small study with a large impact," says study researcher Eric Courchesne, PhD, director of the National Institute of Health-University of California-San Diego School of Medicine Autism Center of Excellence in La Jolla, Calif. "This is an incredibly important discovery that tells us that something started going wrong in prenatal life in children with autism."
The CDC estimates that an average of one in 110 children in the?U.S. has an autism spectrum disorder, a range of developmental disorders that affect the ability to communicate and relate to others.
Some children with autism do have overly large heads, and the new study showed that the brains of boys with autism weighed more than the brains of boys who did not.
"If their brain is too large, there may be too many brain cells. And now we know that the area that shows overgrowth is the prefrontal cortex and this very important for higher-order functions," Courchesne says.
Researchers examined the number and size of neurons among seven boys with autism and six boys without autism. The boys were aged 2 to 16 and had died between 2000 and 2006. They looked at neurons in two areas of the prefrontal cortex -- the dorsolateral (DL-PFC) and mesial (M-PFC).
Specifically, there were 79% more neurons in DL-PFC and 29% more in M-PFC among boys who had autism when compared with boys who did not.
If these findings are confirmed in larger groups of people, it may help researchers identify autism earlier than they can today. The diagnosis of autism is now made on the basis of behavioral assessment around age 2 or 3.
"Earlier intervention leads to improvement all the way around in children with autism. So the need for early diagnosis is there and this will be one of the signatures that will help identify kids at a much earlier age," Courchesne says.
Nicholas Lange, ScD, who co-authored an editorial on the new report, agrees. He is an associate professor of biostatistics at the Harvard University Schools of Medicine and Public Health in Boston.
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