The effects of background illumination and stimulant medication on smooth pursuit eye movements of hyperactive children

Problems with visual information processing have been reported in children with the diagnosis of attention deficit disorder with hyperactivity (ADD H), and deficits in oculomotor control have been posited as an important factor in this phenomenon. To assess aspects of oculomotor performance, smooth pursuit eye movements (PEMs) were recorded electrooculographically in 20 ADD H and 20 age-matched control children and computer-analyzed for discrete (velocity arrests) and global (root mean square error) disruptions. The effects of stimulant medication (methylphenidate), together with manipulations designed to influence behavioral (attention) and physiological (cerebellar) processes involved in PEM performance, were examined. The tracking patterns of nonmedicated ADD H children contained significantly more discrete aberrations on baseline conditions. Although no single experimental manipulation significantly improved tracking performance in ADD H children, combining all experimental conditions did normalize PEMs in these subjects. Slight improvements in PEM performance in association with medication correlated positively with does of madication of with medication-related improvments of behavior. In light of these data, arguments are presented in supported of (a) hyporousal as a contributing factor underlying oculomotor difficulties in ADD H children and (b) subcortical involbment in PEM dysfunction.This research was funded in part by grants from The Hospital for Sick Children Foundation and the Ontario Mental Health Foundation (RTP). The authors thank Susan Anthony, Dr. Pamela M. Cooper, Stella Cowley, Dr. Kathy Margittai, and Ralph Nevins for technical assistance, Martin Gillett for computer programming, Dr. Phil Firestone and the staff of the University of Ottawa Child Study Centre, and Dr. B. Lena of the Family and Child Unit, Ottawa General Hospital, for subject referral.