Moderate Alcohol During Pregnancy: Learning and Behavior in Adolescent Rhesus Monkeys

Abstract

Background: Although high-dose prenatal alcohol exposure is related to cognitive and behavioral impairments in children and adolescents with fetal alcohol syndrome, there is relatively little research on the effects of moderate drinking during pregnancy. We examined learning, memory, and behavior in adolescent rhesus monkeys prenatally exposed to moderate levels of alcohol, psychological stress, or both alcohol and stress. Methods: Forty adolescent rhesus monkey subjects were derived from four groups of female rhesus monkeys that (1) consumed alcohol throughout gestation; (2) experienced prenatal stress; (3) experienced prenatal stress and alcohol consumption; or (4) control group (no alcohol, no stress). The subjects were assessed for number of trials required to reach 90% criterion of correct responses on nonmatching-to-sample task (NMS), followed by trials with delays of 30, 60, or 120 sec. Ratings of behavior during testing were made after each session. Results: Subjects exposed to moderate prenatal alcohol required significantly more trials to reach criterion on the acquisition phase of the NMS task but had no difficulty with delays. Prenatally stressed monkeys showed lower response inhibition or less behavioral restraint, whereas prenatal alcohol plus stress monkeys showed higher activity level and stereotypies compared with controls. High scores on neonatal measures of orientation (attending to novel stimuli) and motor maturity and low scores on irritability, activity, stereotypies, and impulsivity during acquisition were correlated with fewer trials to criterion on acquisition of NMS. Conclusions: NMS trials required to reach criterion and behavior during testing are sensitive to moderate-level prenatal alcohol exposure in monkeys. The most adverse behavioral outcomes (hyperactivity and stereotypies) were associated with prenatal alcohol plus stress, raising concerns that environmental stress might provide the context within which fetal alcohol exposure could promote adverse behavioral outcomes. These effects occurred in the absence of either facial deformities or retarded physical growth.