Implicit strategy affects learning in children with heavy prenatal alcohol exposure

Background: Learning and memory deficits are commonly reported in children with heavy prenatal alcohol exposure. Our recent work suggested that children with heavy prenatal alcohol exposure retained information as well as controls on a verbal learning test but not on a test of nonverbal learning and memory. To better understand the cause of this differential pattern of performance, the current study re-analyzed data from our previous study to determine if the presence of an implicit learning strategy may account, at least in part, for the finding of spared retention. Methods: The current study examined verbal learning and memory abilities in 35 children with Fetal Alcohol Spectrum Disorders (FASD) and 34 nonexposed controls (CON) matched for age (9-16 years), sex, ethnicity, handedness, and socioeconomic status. Groups were compared on two measures of verbal learning, one with an implicit strategy (California Verbal Learning Test-Children's Version; CVLT-C) and one without (Verbal Learning subtest of the Wide Range Assessment of Memory and Learning; VL-WRAML). Results: Children with FASD learned less information overall than children in the CON group. Both groups learned a greater percentage of information and reached a learning plateau earlier on the CVLT-C compared with the VL-WRAML. Groups also showed comparable rates of retention after a delay on the CVLT-C. In contrast, on the VL-WRAML, children with FASD showed poorer retention rates than children in the CON group. Interestingly, children with FASD did not differ from children in the CON group on CVLT-C semantic clustering scores for learning trials I through 3, and greater utilization of semantic clustering was correlated with better learning and memory performance in both groups. This overall pattern of results was not related to overall intellectual level. Conclusions: The finding of spared retention of verbal information on the CVLT-C in our earlier studies may be related to test characteristics of the CVLT-C rather than a finding of spared verbal retention per se, given that spared retention was not found on a separate test of verbal learning and memory without an implicit learning strategy. These results suggest that the use of an implicit strategy positively affected the ability of alcohol-exposed children to learn and retain new verbal information.