Characteristics of horizontal smooth pursuit eye movements to sinusoidal stimulation in children of primary school age.

Previous research about the maturation of the smooth pursuit system has been carried out in newborns and in human infants in the first months of life. A lower gain was found with respect to adults (where gain is close to 1), with frequent saccadic intrusions. On the contrary, no data are available about smooth pursuit response in children. To fill this gap, we analyse in this study the level of maturation reached by children over 7 yr old (the minimum age in which a correct test can be done). Using a cosinusoidal stimulation, the smooth pursuit characteristics (velocity and position gains and phases) evaluated in children are compared to the corresponding parameters in adults. Our data show a clear difference between the two groups, in particular for velocity gain values (which are lower in children), and a larger variability in children. Since the influence of fatigue and prediction appears to be small, we conclude that these differences can be justified both by high level psychological or cognitive factors and incomplete maturation of smooth pursuit system in children.