Deficits in eye movement control in children with fetal alcohol spectrum disorders

Background: Prenatal exposure to alcohol can result in a spectrum of adverse developmental outcomes in offspring, collectively termed fetal alcohol spectrum disorders (FASD). Deficits in executive function-the psychological processes involved in controlling voluntary goal-oriented behavior-are prevalent in FASD. Oculomotor tasks have been designed as highly sensitive tools to evaluate components of executive function. Because of the extensive overlap in the brain areas controlling eye movements and those affected in FASD, we hypothesized that individuals with FASD display specific neurobehavioral abnormalities that can be quantified with eye movement testing. Methods: Subjects (8-12 years old) were instructed to look either toward (prosaccade) or away from (antisaccade) a stimulus that appeared in the peripheral visual field. Two fixation conditions were used. In the gap condition, the central fixation point (FP) was removed before the appearance of the peripheral stimulus; in the overlap condition, the FP remained illuminated. Saccadic reaction times (SRTs, time from stimulus appearance to saccade initiation), direction errors (saccades made in the incorrect direction relative to instruction), and express saccades (short-latency: SRT=90-140 ms) were measured to assess automatic and volitional saccade control. Results: Compared with controls, FASD children had elongated reaction times, excessive direction errors, and no express saccades. Metric analysis of correct prosaccades revealed a trend toward increased saccadic duration and decreased saccadic velocity in FASD subjects. Conclusion: These results reflect deficits in executive function and motor control, and are consistent with dysfunction of the frontal lobes, possibly due to disrupted inhibitory mechanisms. Therefore, eye movement tasks may be powerful and easy tools for assessing executive function deficits in FASD.