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New research suggests possibility of common underlying biology in children who develop autism

March 27, 2014 at 6:26 PM EDT
As the U.S. government increases its estimate of the prevalence of autism to being one in every 68 children, scientists have announced new research that shows there may be a common disruption in parts of the brain essential to emotions, communication and social function, beginning during pregnancy. Judy Woodruff learns more from Eric Courchesne of University of California, San Diego.
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JUDY WOODRUFF: Let’s turn to some new findings on autism, especially research showing brain changes happening in the womb. Scientists compared the brain tissue of children who had autism and died with those who didn’t have autism. They found that kids with autism had disorganization in regions of their brain essential for social functioning, emotions and communication, a conclusion drawn from discovering disruptions in these sections of the brain. Those gaps are shown here in purple.

The news came as the government revised upward its estimate of the prevalence of the disorder to one out of every 68 children in the U.S. That’s more than the previous autism estimate of one out of every 88 kids.

Eric Courchesne is an author of today’s research about the brain. He’s the director of the Autism Center of Excellence at the University of California, San Diego.

Eric Courchesne, what makes these findings important?

ERIC COURCHESNE, Autism Center of Excellence, University of California, San Diego: It’s especially important to try to understand what is causing autism, in order to address this really high rate of one in 68 autistic individuals.

The — for years, it’s been really an effort to discover what starts it. And we did the study that points to the second and third trimester. And little patches of cortical disorganized defects are present in frontal cortex and temporal cortex. Those are the areas of the brain that are most important for social, language and communication functions.

Those are the functions that are impaired in autism. The study that we did was a very detailed one, examining the fine structure of cells and layers in cortex. The layers — there are six layers in cortex. We found that layers two, three, four, five, and six are very commonly disrupted.

Those layers are typically formed between about 19 weeks of gestation and about 30 or 30 weeks of gestation.

JUDY WOODRUFF: So, that’s what I was trying to understand. This is the cortex being an area that is on the outer side, the outer lining of the brain, if you will. And so what you found — how do you know, though, that these occurred early in pregnancy or relatively early?

ERIC COURCHESNE: So, it’s known from our from other studies that if — that, as the brain is developing from the second to the third trimester, that the brain goes from displaying a single layer in cortex — the cortex is the gray matter.

So, probably when your mother asks you to pay attention and to use your gray matter, she was talking about the cortex, where brain cells are located. The cortex is only about three millimeters thick. It’s pretty big sheath, but it has six layers. Each layer has specific types of cells.

Each one of those cells does a specific type of information processing. They all have to interact with each other. Cortex is formed in the second trimester. Initially, there is a single layer, then several layers, and then finally by about the third trimester, there are six layers.

Throughout that process, there are markers that indicate when those layers are forming, so there is a progression of development from not being defined, to being fully defined, where each cell type is defined by a genetic signature. We examined those genetic signatures.

And what we discovered was that there were places within the frontal cortex where those genetic signatures were absent, suggesting that this progression from being undefined to being defined as several layers and finally six layers in some — at some point failed to take place.

JUDY WOODRUFF: And what — what you can tell from this about what the cause or causes might be?

ERIC COURCHESNE: Well, there are a number of different possibilities.

One study recently would suggest that there’s a possible genetic cause that could be accounting for what we identified. But then there’s also the possibility that there could be environmental or maternal intrauterine events that are non-genetic that might be involved.

So the next steps in the sort of research is to identify what the triggers are that cause the failure of the normal progression of development of these six — the normal development of these layers of brain — of the cortex of the brain.

JUDY WOODRUFF: So you’re not able at this point to narrow it down? You said either genetic or environmental. Could be either one?

ERIC COURCHESNE: Or it could be a combination…

JUDY WOODRUFF: Combination.

ERIC COURCHESNE: … which could be that both are required.

But it does narrow it down to a very important point, which is that this evidence points to brain maldevelopment in autism beginning in pregnancy, very likely in the second and third trimesters, to a particular important part of the brain that’s important for the kinds of symptoms that are seen in autism.

It narrows it down to a type of defect that is common across the children in our — the autistic children in our study. In fact, about 91 percent of the children in our study displayed this defect. And that’s very exciting and unexpected, because autism is a clinically heterogeneous disorder. So many would have assumed that there would be lots of different types of defects, not one common type of defect.

So what we found is very interesting because it suggests there could be a common underlying biology that is there at the beginning, so a common time, a commonplace, a common underlying neuropathology that begins this disorder. That will really help the search for the original triggers that cause autism. And it changes the direction of research from postnatal to prenatal.

JUDY WOODRUFF: And so — and so my question is, is, what does it tell you about prevention, if anything?

ERIC COURCHESNE: It tells us what studies to do to determine what the triggers are. Knowing what the triggers are will then tell, reveal what prevention might be possible.

But it also gives clues as to what might be biomarkers for identifying autism at very young ages, perhaps as early as at the age of 1 to 2 years, so that kids can be identified at much younger ages, be referred for treatment at much younger ages, and thereby have a better outcome.

JUDY WOODRUFF: Well, there is — it’s fascinating research. And we appreciate your joining us, Eric Courchesne. Thank you.

ERIC COURCHESNE: Well, thank you. It was good to be here.