More Signs Autism May Originate During Pregnancy
Brain-tissue samples show differences linked to prenatal development
For the new study, Lein and his colleagues examined small samples of the neocortex -- the outer surface of the brain. During fetal development, the neocortex forms six layers, each with its own specialized brain cells. As those cells develop, they take on a "genetic signature" that can be visualized in tissue samples, using sophisticated techniques.
Overall, the study found, brain tissue from children with autism showed tiny patches where certain genetic signatures were absent from brain cells.
What's more, those patches were concentrated in areas associated with higher order brain functions, such as understanding language and social cues.
"That makes sense," Kaufmann said. "Those are the areas where you would expect to find abnormalities."
The phenomenon, he said, was seen in 10 of the 11 autistic children, even though the severity of their symptoms varied. Some, for example, had been diagnosed with intellectual disability, while others had not.
Lein said the fact that the brain tissue showed small patches of disruption, rather than pervasive abnormalities, is "potentially good news." It suggests that much of the neocortex is actually typical in children with autism, he said.
That might help explain why autistic toddlers who get early behavioral therapy often show significant improvements, Lein said. It's possible the brain is able to "rewire," to an extent, to get around some of the trouble spots seen in this study.
In general, experts say the earlier such therapy starts, the better. The problem is, most children are not diagnosed with autism until after they reach age 4, according to the U.S. Centers for Disease Control and Prevention.
Kaufmann said researchers are working on finding objective "biomarkers," such as proteins in the blood, that could be used to detect autism earlier. But any such tests are a long way off, he said.