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Entries in Journal of American Medical Association (1)

Tuesday
Nov082011

Study: Autistic Brains Have Abnormal Number of Brain Cells

BananaStock/Thinkstock(WASHINGTON) -- A new, small study provides a tantalizing clue to the causes of autism, suggesting that children with the disorder have heavier brains and an overabundance of brain cells called neurons.

Autism researchers had suspected for more than a decade that the disorder might be the result of abnormal brain growth and development. Previous studies have shown that autistic children have larger heads and brains, and that brain regions crucial for social, emotional, and communication processing are particularly overgrown.

This study, however, is the first to provide hard evidence of brain development gone awry in autistic children, gleaned from actual counts of these brain cells.

In the study, published Tuesday in the Journal of the American Medical Association, scientists investigated the brains of 13 boys from ages 2 to 16, whose brains were donated for scientific study after they died. Using a precise microscopic technique, the researchers counted the neurons in the brains of these children, seven of whom had autism and six who did not.

They found that the brains of the autistic children had 67 percent more neurons in a region called the prefrontal cortex, an area linked to social, emotional, and communication processing— functions that are typically lacking in autism.

The brains of the autistic children also weighed an average of 17.5 percent more than the brains of children without the disorder.

Eric Courchesne, the study's lead author and a neurobiologist at the University of California, San Diego Autism Center of Excellence, called these differences "dramatic and surprising."

"We didn't expect to see such a big effect," Courchesne said. "Since the brain doesn't generate new neurons in the prefrontal cortex after birth, we know that this happens during prenatal development. So this points to something going wrong with how the brain initially forms itself in autistic children," he said.

Many researchers point out that these new findings are very preliminary and don't apply to children and families currently dealing with autism. The study was very small, and currently, there is no way to analyze the brain tissue of living children.

But it does give researchers a tantalizing avenue for future research on the causes of autism. Courchesne noted that studies finding genetic links to the disorder are also crucial to understanding how it develops.

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ABC News Radio