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TAMPA — Abnormal brain growth in children with autism suggests that the disorder begins before birth, according to a new study involving research at the University of South Florida.
Researchers found that children with autism had significantly more neurons in the region of the brain involved in socializing and communication, abilities in which autistic children are lacking.
Since these neurons develop during pregnancy, the finding weakens controversial theories that autism is caused by vaccination or other exposures in early childhood, said USF researcher Peter Mouton, co-author of the study published Wednesday in the Journal of the American Medical Association.
Being born with too many brain cells in the prefrontal cortex may impair the ability of autistic children to process information like children without autism, he said.
In recent years, mounting scientific evidence has proved that concerns about a link between vaccines and autism are unfounded. This latest study, which examined brain tissue from seven deceased autistic children, further weakens that argument.
During normal fetal development, Mouton explained, excess neurons are eliminated. But that process went awry in the autistic children studied. The result: the cognitive equivalent of a traffic jam, much like what would happen if a series of small roads was built across an interstate, Mouton said.
"There's a possibility that this is the brain trying out new pathways," he said. "Sometimes they work and you have Albert Einstein or Steven Jobs. And sometimes they don't work and you have kids that are locked in."
The study did not offer new insight into what causes autism — just how it develops. Still, researchers believe they are the first to quantify the link to abnormal brain growth in young children.
The research team compared the brain tissue of seven autistic boys and six boys without the disorder. The boys, all between the ages of 2 and 16, had died of causes not related to the disorder.
Tissue samples were sent to the USF's Byrd Alzheimer's Institute, where Mouton specializes in analyzing brain pathology and cell biology. For the autism study, he used the same technology being applied to examine brain changes in Alzheimer's disease.
With each sample, Mouton didn't know if he was looking at brain tissue from an autistic boy or from the control group. But after sending in all the data, he received a phone call from the lead researcher in California.
"He said, 'Peter, I just broke the code!' " Mouton recalled.
The analysis found that the children with autism had 67 percent more neurons in the prefrontal cortex, as well as heavier brains, compared to boys without the disorder.
That knowledge helps to focus the attention of researchers on this critical region of the brain, said Dr. Thomas Insel, director of the National Institute of Mental Health, in a news release.
But the findings are limited by the size — few brain samples were available to study — and the fact that it involved only boys. Researchers now hope to conduct larger studies and to begin looking for a common genetic mutation involved in autism.
"We really would just like to know what causes autism," Mouton said.
Letitia Stein can be reached at lstein@sptimes.com or (727) 893-8330. For more health news, visit www.tampabay.com/health.
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