The Use of Open- and Closed-Loop Control During Goal-Directed Force Responses by Children with Heavy Prenatal Alcohol Exposure.

ABSTRACT

BACKGROUND: Many daily functional activities involve goal-directed responses based on open-loop and closed-loop motor control, yet little is known about how children with heavy prenatal alcohol exposure organize and regulate these 2 types of control systems when completing a goal-directed force response. METHODS: Children with (n = 19) or without (n = 23) heavy prenatal alcohol exposure were required to match a target force (25 and 50% of maximum voluntary force) in a specified target time (200, 800, and 2,000 ms). Target force and produced force were visually displayed on a computer monitor. The analog force-time record was parsed into 2 segments the period beginning from force initiation to the first reversal in force was designated the open-loop phase, and the remainder of the response was the closed-loop phase. RESULTS: Compared to controls, alcohol-exposed children produced a significantly shorter duration of open-loop control, a higher open-loop phase rate of force development, a shorter time to reach maximum force during the closed-loop phase, and greater absolute target force error. Increasing target force magnitude did not differentially alter the performance of the clinical group. CONCLUSIONS: The results indicate that alcohol-exposed children experience deficits in completing goal-directed force responses that likely stem from an alcohol-related insult to the central nervous system. Therapeutic exercises should be designed to recalibrate internal timing systems and improve visuomotor integration.