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Eye movement tasks can be used to assess fetal alcohol spectrum disorders

February 23, 2007

Fetal alcohol spectrum disorders (FASD) refers to a wide array of adverse developmental outcomes in children due to prenatal alcohol exposure. FASD is more widespread than Fetal Alcohol Syndrome, which is more severe, but FASD is harder to accurately diagnose because of fewer objective diagnostic tools. New research indicates than simple eye-movement or oculomotor tasks can be used to assess individuals with FASD.

Results are published in the March issue of Alcoholism: Clinical & Experimental Research.

"Whereas oculomotor tasks have been used to assess brain function in a number of different clinical populations, this is the first such study to be carried out in FASD children," said James N. Reynolds, professor of pharmacology & toxicology at Queen's University and corresponding author for the study. "We wanted to assess the feasibility of using this tool to probe different aspects of brain function and behavior in this specific clinical population."

The impetus for this research was a casual conversation on an airplane on the way back from a neuroscience conference, said Reynolds. "I had been wrestling with the problem of translating basic science research into relevant clinical studies of individuals affected by prenatal exposure to alcohol," he recounted. "There were few, if any, objective tools that could be used to assess brain function in FASD subjects." In the end, Reynolds collaborated with coauthor Doug Munoz, who had for years been using eye-movement tasks to study brain function and behavior in different clinical populations, including children.

Study authors compared the oculomotor performance of 10 children with FASD (4 males, 6 females) with 12 age-matched control subjects (6 males, 6 females). All were instructed to either look toward (prosaccade) or away from (antisaccade) a stimulus that appeared in their peripheral visual field. Researchers measured reaction times, direction errors, and short-latency express saccades (very short latency eye movements).

"We found that FASD children had much longer reaction times - defined as the time required to initiate eye movement - both towards and away from the peripheral visual target," said Reynolds. "FASD children also made a greater number of direction errors, even in the more simple prosaccade task, and exhibited a dramatic reduction in express saccades."

Reynolds is pleased that he and his colleagues have discovered what seems to be a powerful and yet easy tool for assessing executive-function deficits among individuals with FASD.

"In the absence of confirmed maternal alcohol consumption during pregnancy," he said, "the diagnosis of FASD remains a significant clinical challenge. This is especially true when the characteristic facial features are absent, and subtle neurobehavioral problems are the primary feature. Furthermore, many of the children affected by prenatal alcohol exposure live in remote communities, lacking access to FASD diagnostic clinics and sophisticated neuroimaging technology. Moreover, comprehensive evaluation requires the ability to track changes in brain function longitudinally."

Largely due to the findings of this research, Reynolds and his research team have acquired a mobile eye-tracker unit that hooks up to a laptop computer, allowing them to move their research program out of the laboratory and into the communities.

"We have already visited several communities in Ontario, and are establishing collaborations with other research centers across Canada," he said. "At the same time, we have initiated a study of children and young adults performing these same eye-movement tasks while brain activity is recorded using functional magnetic resonance imaging (fMRI). We also plan to apply our findings to other developmental disorders, such as Attention Deficit Hyperactivity Disorder. In this way, we will establish a large database that will enable us to make direct comparisons of task performance and brain function across multiple clinical populations."

Alcoholism: Clinical & Experimental Research