While children with fetal alcohol syndrome (FAS) have identifiable craniofacial abnormalities, children with alcohol-related neurodevelopmental disorder (ARND) can have significant cognitive impairments without facial anomalies. An important new study has found that a deficit in eyeblink conditioning (EBC) can identify children with probable FAS, and may also serve to identify alcohol-exposed children who lack distinctive FAS features.
Results are published in the February issue of Alcoholism: Clinical & Experimental Research.
“Eyeblink conditioning (EBC) is a Pavlovian paradigm that involves temporal pairing of a conditioned stimulus, such as a tone, with an unconditioned stimulus, such as an air puff,” explained Sandra W. Jacobson, a professor in the department of psychiatry and behavioral neurosciences at Wayne State University School of Medicine, and first author of the study. “Animal studies have shown that binge consumption of alcohol during pregnancy impairs EBC. We wanted to see if we could use the EBC paradigm to identify underlying or subcortical deficits that are specifically affected by prenatal alcohol exposure in children.”
“The present study provides the first documentation that clearly points to an FAS relationship because of the large sample size, the prospective follow-up of children from birth, and the careful measurement of prenatal exposure to alcohol and other drugs,” said Lynn T. Singer, Deputy Provost and vice president for academic programs at Case Western Reserve University. “Moreover, the deficits in EBC were not related to IQ or [found in nonexposed children with] microcephaly, which are often confounding factors.”
Jacobson knew from previous visits to the Western Cape Province of South Africa that there was an extremely high incidence of FAS in the region. In fact, the prevalence of FAS in the mixed-ancestry population is among the highest in the world. Although the traditional dop system – under which farm laborers were paid in part with wine – has been outlawed, heavy alcohol consumption persists in some regions, especially binge drinking on the weekends. Jacobson and her colleagues have been studying a group of women and their children since 1998, leading to this, the first prospective, longitudinal study of children with FAS.
The researchers administered three sessions of EBC to 98 five-year-olds born to mixed-ancestry women in Cape Town, pairing a tone with an air puff. Normally, after repeated pairings, a child as young as five months old will develop a conditioned eyeblink response. In addition to the EBC sessions, expert dysmorphologists assessed FAS status among the five-year-olds.
“Even knowing the high incidence of FAS that has been documented in rural areas of the Western Cape province, we were surprised to see the very high incidence of children born with FAS and partial FAS (PFAS) in this urban mixed-ancestry cohort,” said Jacobson. “Twelve (18.8%) children born to the 64 heavy drinking mothers met criterion for FAS, and an additional 18 (28.1%) for PFAS. Not a single child with FAS at this age met criterion for short-delay conditioning as contrasted with 75 percent of the controls. In addition, about two-thirds of the children with PFAS and two-thirds of the heavily exposed nonsyndromal children also did not meet criteria for conditioning. Given that we controlled for IQ and that EBC was not impaired in non-alcohol-exposed children with microcephaly, these findings suggest that the EBC deficit does not reflect impaired intellectual ability but rather is a direct effect of the fetal alcohol exposure.”