he symptoms of autism may not be obvious until a child is a toddler, but the disorder itself appears to begin well before birth. Brain tissue taken from children who died and also happened to have autism revealed patches of disorganization in the cortex, a thin sheet of cells that's critical for learning and memory, researchers report in the New England Journal of Medicine. Tissue samples from children without autism didn't have those characteristic patches. Organization of the cortex begins in the second trimester of pregnancy. "So something must have gone wrong at or before that time," says Eric Courchesne, an author of the paper and director of the Autism Center of Excellence at the University of California, San Diego. The finding should bolster efforts to understand how genes control brain development and lead to autism. It also suggests that treatment should start early in childhood, when the brain is capable of rewiring to work around damaged areas.
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