In 1996, the Institute of Medicine made an initial step towards addressing the confusion and controversy regarding the diagnosis of fetal alcohol syndrome (FAS) by proposing a classification scheme and calling for research to evaluate its validity and clinical utility. Previous research evaluated memory, executive functions, and behaviour problems in FAS. Prior to the present study, however, there had not been an empirical evaluation of the existence of a spectrum of diagnostic subgroups or an evaluation of subgroup functioning on neuropsychological components of attention during the pre-teen and adolescent years. Part 1 of this study used categorical data regarding diagnostic domains to determine if an a priori spectrum of four subgroups could be identified. This spectrum included FAS and three fetal alcohol effect (FAE) subgroups, which were defined using teratogenic theory, previous research findings, and logic. The sample consisted of 112 children with a confirmed history of excessive prenatal alcohol exposure. Part 2 evaluated the continuity and comparability of the CNS dysfunction subgroups exhibited by assessing neuropsychological components of attention using models by Mirsky and Conners. The sample consisted of 30 children and subgroups were matched on age, sex, and living situation. Results identified 3 of the 4 potential subgroups. All subgroups exhibited a clinically significant attention deficit. After adjusting for IQ, the FAS and FAE subgroups had comparable levels of functioning on all components of attention with one exception. On the sustain component, the FAE subgroups had more difficulties than the FAS subgroup in maintaining a consistent response-speed in response to changes in the length of time between targets. This study provides empirical and theoretical support for the validity and clinical utility of a spectrum of fetal alcohol subgroups consistent with the IOM's classification. It furthers a theoretical understanding of the dose-response effects of alcohol as a teratogenic agent. It suggests that attention regulation functions are especially vulnerable to the damage caused by prenatal alcohol exposure. The findings emphasize the importance of obtaining a history of prenatal alcohol exposure in individuals presenting with neuropsychological difficulties, and developing treatment programs for pregnant women with an alcohol addiction.

Two groups of male and female rats were given the same dose of alcohol using an artificial rearing procedure on postnatal days 4-10. One group received the alcohol in a condensed manner each day which caused cyclic blood alcohol concentrations (BACs) with high peaks. A second group received the alcohol in a uniform manner over each day which resulted in moderate, stable BACs. Two control groups consisted of male and female rats artificially reared but not exposed to alcohol and rats reared normally by dams. All rats were raised to 90 days of age and then tested for spatial navigation ability in the Morris water maze, which involved locating a hidden underwater platform using distal extramaze cues. Neither the alcohol treatments nor the artificial rearing had any effects on performance of adult male rats relative to suckle controls in this task. In contrast, the condensed alcohol exposure but not the uniform alcohol exposure resulted in detrimental performance in the Morris water maze by adult female rats. When the ability to locate and escape onto a visible platform was examined, there were no differences between the female groups given condensed alcohol exposure or artificially reared on milk solution alone. Thus, exposure to high BACs during the brain growth spurt has a lasting and selective detrimental effect on spatial navigation learning in adult female but not adult male rats.