Over the past decade, there has been increasing concern about the effects of cocaine use during pregnancy on the developing fetus. Results from studies of school-aged youngsters who were exposed to cocaine in the womb are now starting to emerge. However, most of these studies allow only cautious conclusions because of many confounding factors—maternal use of drugs other than cocaine, maternal stress, and prenatal and postnatal malnutrition, for example.

So Barbara Strupp, Ph.D., an associate professor of psychology and nutritional sciences at Cornell University in Ithaca, N.Y., and her coworkers decided to do an animal study to better understand the effects of prenatal cocaine exposure on mental performance. They report, in the August Behavioral Neuroscience, that whereas prenatal cocaine exposure does not seem to affect many areas of cognition, it does impair selective attention.

Strupp and her colleagues surgically implanted catheters into pregnant rats, half of whom received doses of cocaine comparable to human recreational doses, and half of whom received a saline solution. Both the cocaine-exposed fetuses and the control fetuses were followed up once they were born to see whether there were any differences between the two groups in cognitive-behavioral abilities.

The cocaine-exposed rats did not differ from the control rats on basic learning ability, short-term memory, long-term memory, impulse control, ability to shift attention, or cognitive and behavioral flexibility, the researchers found. However, the cocaine-exposed rats differed from the control rats in their ability to pay selective attention—that is, they had trouble staying focused despite environmental distractions.

Strupp and her team speculate that their results might be applied to children who were exposed to cocaine in the womb. The type of deficit seen in the study, Strupp said, "could have serious effects on the school performance of affected children."

Brain anatomy studies support the finding of Strupp and her coworkers. The brain areas that appear to be involved in selective attention—the locus ceruleus and/or cingulate cortex-thalamic circuitry—have been found to exhibit lasting changes as a result of prenatal cocaine exposure.