Decades of research have left little doubt that prenatal alcoholexposure has adverse effects on intellectual and neurobehavioraldevelopment. A recent study of the effects of moderate to heavyprenatal alcohol exposure on cognitive function confirms earlierfindings of slower processing speed and efficiency, particularly whencognitive tasks involve working memory. Results are published in theAugust issue of Alcoholism: Clinical & Experimental Research.
"Prenatal alcohol exposure is often associated with slower reactiontimes and poorer attention in infancy, and some of these deficits maybe at the core of poorer academic performance and behavior problemsoften seen later in childhood," said Matthew J. Burden, postdoctoralresearch fellow at Wayne State University School of Medicine andcorresponding author for the study. "In cases of fetal alcohol syndrome(FAS) -- lower IQ scores are common, often reaching the level of mentalretardation. This is because alcohol consumed by the mother has adirect impact on the brain of the fetus. However, full FAS is notrequired to see this impact; it is just less obvious to detect acrossthe array of exposures found in fetal alcohol spectrum disorders(FASD), which include effects of prenatal alcohol at lower drinkinglevels."
Julie Croxford, graduate research assistant at Wayne State University,says there is a need for researchers to look at the damage caused byprenatal alcohol exposure at lower-than-heavy levels of drinking. "Inthe past, much focus was placed on studying the full-blown FAS," shesaid. "More recent research has considered those individuals damaged bylower levels of exposure. This is an important focus."
For this study, researchers assessed 337 African-Americanchildren (197 males, 140 females) at 7.5 years of age; selected fromthe Detroit Prenatal Alcohol Longitudinal Cohort, the children wereknown to have been prenatally exposed to moderate-to-heavy levels ofalcohol. Their mothers were originally recruited between September 1986and April 1989 during their first prenatal visit to a maternityhospital clinic. The children were assessed on processing speed andefficiency in four domains of cognitive function -- short-term memoryscanning, mental rotation, number comparison, and arrow-discriminationprocessing -- using a Sternberg paradigm, which examines speed ofcompletion as problems become increasingly more difficult.
"We chose these four domains because they allow us to study distinctaspects of cognition within the same cognitive framework," said Burden."This helps to distinguish potentially specific deficits from thosethat are more global in nature; that way we get a better understandingof how prenatal alcohol exposure affects cognitive functioning manyyears later in childhood. We used the Sternberg paradigm because itindicates how fast an individual generates the correct response to anumber of problems, providing an overall measure of speed; and it examines the rate at which response times increase as problem difficulty increases, providing a processing efficiency measure."
Although the alcohol-exposed children were able to perform as well asthe other children when tasks were simple -- such as naming colorswithin a timed period -- when pressed to respond quickly while havingto think about the response, their processing speed slowed downsignificantly.
"This suggests that processing speed deficits are more likelyto occur within the context of some cognitive demand," said Burden. "Wealso found that prenatal alcohol exposure was associated with poorerefficiency on number processing, a finding consistent with pastresearch showing more specific adverse effects in the arithmeticdomain. Arithmetic performance may be relatively more compromised withprenatal alcohol exposure than other types of intellectual performance,such as verbal abilities. We also looked at how processing speedrelated to other aspects of cognition, working memory in particular.Prenatal alcohol exposure had some impact on both speed and workingmemory, but the effect on working memory was partly accounted for bythe deficits in speed -- in other words, slower performance contributesin part to poorer working memory."
"The conclusion drawn here is that the reaction-time deficitsassociated with prenatal alcohol exposure are seen more indemanding/challenging cognitive tasks that involve the integration ofworking memory," said Croxford. "The real-world implications of thisare that children exposed prenatally to alcohol may be able to performsimple tasks, but may struggle with tasks that are more challenging andrequire complex cognition and the use of working memory. This is likelyto mean that these children may be more and more challenged the olderthey get by the demands placed on them within the school system andwithin their day-to-day social interactions."
Both Burden and Croxford noted that this study also examined the impactof "confounding" factors such as home environment, socioeconomicstatus, and current maternal drinking levels, which researchers believemay contribute to the poor outcomes seen in children exposed toprenatal alcohol.
"In this study, we accounted for more than 20 of these potentiallyconfounding influences in the analyses," said Burden. "The effect ofalcohol exposure in utero persisted above and beyond any other influences present."
What this means, said Croxford, is that alcohol itself causes specific,identifiable and permanent deficits in brain development andphysiology. "This reinforces the current public health message thatwomen should not drink alcohol during pregnancy," she said.
Burden said that he and his colleagues will continue to examine thelong-term effects of prenatal alcohol exposure on the same children."In addition to neuropsychological and behavioral measures, we willalso be using electrophysiological techniques such as event-relatedpotentials and neuroimaging (fMRI) to more directly connect cognitiveperformance with brain function," he said.
Alcoholism: Clinical & Experimental Research (ACER) is theofficial journal of the Research Society on Alcoholism and theInternational Society for Biomedical Research on Alcoholism. Co-authorsof the ACER paper, "The Relation of Prenatal Alcohol Exposure toCognitive Processing Speed and Efficiency in Childhood," were: SandraW. Jacobson of the Department of Psychiatry and BehavioralNeurosciences at Wayne State University School of Medicine; and JosephL. Jacobson of the Departments of Psychiatry and BehavioralNeurosciences, Obstetrics/Gynecology, and Psychology at Wayne StateUniversity. The study was funded by the National Institute on AlcoholAbuse and Alcoholism, the National Institutes of Health, and the Stateof Michigan.
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