Researchers find abnormality in brain layers of autistic children

By Gene Emery

NEW YORK (Reuters Health) - Researchers say they have uncovered key abnormalities in some of the layers of the brains of children with autism, an indication that the foundation for the problem is laid early in fetal development.

Using a unique collection of molecular tags applied to the brains after the children had died, they found patches along the convoluted surface of the brain where some usual components of cells were missing.

Brain cells were still present in those patches, but they lacked proteins seen in normal brain cells, said Dr. Rich Stoner, coauthor of a paper on the results that appears in the March 27 New England Journal of Medicine.

The team used the tags to look for 25 unique markers of healthy cells and of specific genes in the brains of children who had died between the ages of 2 and 15 years. The telltale patches were found in 10 of 11 children who had been diagnosed with autism when they were alive and missing from 10 of 11 unaffected children.

The telltale patches don't always appear in the same location from brain to brain. That dovetails with the fact that autism symptoms can vary from person to person, Stoner said.

"Each patient's constellation of symptoms may depend strongly on where the patches occur and how many of them there are," said Stoner, of the University of California San Diego Autism Center of Excellence.

How those patches affect behavior is not known, he told Reuters Health.

They were seen in the frontal cortex, the portion of the brain that handles social cues and complex communication, and the temporal cortex, which is involved in language. Patches were not seen in the visual cortex, which helps control perception.

"This defect indicates that the crucial early developmental step of creating six distinct (brain) layers with specific types of brain cells - something that begins in prenatal life - had been disrupted," Eric Courchesne, coauthor and director of the center, said in a news release.

"It's a really interesting study," Dr. Sophie Molholm, an associate professor of pediatrics and neuroscience at Albert Einstein College of Medicine, told Reuters Health by phone. "What they've shown is that regions of the cortex that have been implicated in autism already have an unusual organization that's really suggestive of the abnormalities and processes" in the disease.

"A number of studies show that people with autism might be better at detecting the features of auditory stimulus but not the whole message," said Molholm, who was not connected with the new research. "People with autism might have more of a tendency to focus on pitch and changes in pitch, or loudness (than the words of a message), and that can be distracting and detracts from the task at hand."

In the study, some patches were appearing in the region of the brain that would control those abilities.

Because the symptoms vary from person to person, "It's not incredibly surprising that they don't find (a patch) in every case, and it's compelling they don't find it in the control cases, except for one situation," Molholm said.

"I'm hoping (the new findings) are going to drive more research in this area so we can figure out what these are and figure out what the cells are like in these regions, and start to integrate this with some of the genetic findings as they're coming out over the past year or two," Stoner said.

The team had previously discovered that children with autism tend to have heavier brains and 67% more neurons in the prefrontal cortex, which plays a role in social behavior, decision making and personal expression.

SOURCE: http://bit.ly/1hVcVdJ

N Engl J Med 2014;370:1209-1219.

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