The brains of children with autism contain a built-in patchwork of defects, suggesting that the developmental disorder begins while they are growing in the womb, reported a study Wednesday.
Researchers described their findings in the New England Journal of Medicine as "direct evidence" of a prenatal origin for autism, which affects as many as one in 88 children in the United States and has no known cure.
"Building a baby's brain during pregnancy involves creating a cortex that contains six layers," said co-author Eric Courchesne, professor of neurosciences and director of the Autism Center of Excellence at University of California, San Diego.
"We discovered focal patches of disrupted development of these cortical layers in the majority of children with autism."
For the study, researchers dissected brain tissue from 11 children, aged 2 to 15, who had been diagnosed with autism spectrum disorder (ASD) and who had died, most of them by drowning.
Looking for a specific set of 25 genes that had "robust, consistent, and specific expression patterns in the cortex," they compared them to brain samples from 11 children without autism, said the study.