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Drug Exposure Before Birth Could Affect Kids' Decision-making Skills

Medical News Today, November 12, 2006

The part of the brain responsible for making most decisions about how to behave seems to develop less quickly in children exposed to cocaine before they were born, University of Florida researchers have found.

Using a new form of magnetic resonance imaging, researchers compared 28 adolescents exposed to a mix of cocaine and other drugs in the womb with 25 children whose mothers did not use cocaine during pregnancy and pinpointed subtle differences in how the brain's frontal lobe developed. Researchers noticed that pathways in the frontal lobe, which connect to other parts of the brain to send information, were not as well-defined in children exposed to cocaine before birth, according to findings published this month in the journal Pediatrics.

The children exposed to cocaine also fared slightly worse on tests designed to assess skills linked to the frontal lobe, such as when to act and when to stop, said Tamara D. Warner, Ph.D., a UF research assistant professor of pediatrics and the study's lead author.

"We actually found that there is a relationship between the behavior and the brain," Warner said. "There were significant associations with how well children were able to do certain tasks and how well-developed the connections in the brain were."

Some of the children whose mothers did not use cocaine were exposed to alcohol, tobacco and marijuana, but they did not exhibit the same subtle differences in the brain. Because the mothers of children exposed to cocaine used multiple drugs, how these drugs interacted was likely a big part of the problem, Warner said. The mothers had taken cocaine and varying combinations of alcohol, marijuana and tobacco, and the interactions among these drugs often are complicated, sometimes producing additional toxic substances, Warner added.

To get a better glimpse of the frontal lobe, researchers used a form of imaging that allowed them to see how water flows through pathways linked to other parts of the brain. How the water moved through these channels showed the researchers how developed these pathways were in each child's brain. The pathways were more mature in children whose mothers did not use cocaine and not as well-formed in the children whose mothers had, the study showed.

The children, who ranged in age from 10 to 12 and were from similar socioeconomic backgrounds, also participated in two behavioral tests that Warner likened to "Simon Says" types of activities. On one test, children were asked to look at the word "red" but then name the color of the ink used to write the word. This showed how well they were able to ignore the instinct to read the written word and give the correct answer. On another test, which Warner likened to "connect the dots," children were asked to connect a series of numbers in order on a page and then perform a similar exercise alternating between numbers and letters. The children in the drug-exposed group named fewer colors correctly and took longer to adapt to connecting both numbers and letters, Warner said.

Including observations about how the brain looks and behavioral test results in the study is important because it links an actual brain change in children to a behavior change, said Lynn T. Singer, a professor of pediatrics, psychology and general medical sciences at Case Western Reserve University who also studies prenatal cocaine exposure in children.

"This is one of the first findings that shows there is a difference in the way the brain works in (children exposed to cocaine)," Singer said. "It's a very important study in that we're getting new evidence of specific brain changes. The way the brain is wired is different for these children."

Despite these subtle signs of damage, UF researchers say children exposed to cocaine before birth are still faring far better than people predicted in the 1980s, when they were dubbed "crack babies." Past studies at UF and other institutions have shown that children exposed to cocaine before birth exhibit no more behavioral problems as toddlers than other children, have average IQ scores and face only slight problem-solving difficulties in school.

But the biggest questions won't be answered until the children age, Warner said. Researchers do not know yet how these differences in the brain's frontal lobe will affect children as they enter their teen years and are faced with peer pressure and tough decisions.

"Not knowing when to stop and when to inhibit your behavior could have much wider consequences than a Simon Says game," Warner said. "The differences we found were intriguing, but they really are the first piece of the puzzle in understand how these children are developing."

University of Florida Health Science Center
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