Abstract
Abstract: :
Purpose: The purpose of this study was to elucidate the contribution of cerebellar mechanisms to the fine control of saccades and smooth pursuit, both during development and during adaptation to altered environments. Methods:We examined the eye movement responses of three populations of subjects; infants, children with cerebellar disorders and normal adult subjects placed in novel inertial environments; e.g., during inverted viewing of visual targets. For direct comparison of smooth pursuit and saccades in the different subject groups, identical point stimuli were either pseudorandomly stepped or smoothly moved sinusoidally in front of subjects in an otherwise darkened laboratory environment. Eye movements were monitored with EOG, VOG and scleral search coil. Results: We observed similar eye movement dysmetrias in each group of subjects, suggesting the possibility of a common cerebellar mechanism. Saccades were hypometric or hypermetric, late and slow in all three subject groups. With adaptation, the adults recovered normal saccades. Pursuit gains were reduced and numerous saccadic intrusions, including square wave jerks, were observed in each subject group. Conclusion: We conclude that the maturation of infant saccades and pursuit parallels the changes seen in adaptation to novel visual and inertial environments. Furthermore, the striking similarity between the eye movements of normal infants and children with cerebellar disorders suggests that the immaturities seen in infants are related to delayed maturation of cerebellar function.
Keywords: 495 ocular motor control • 406 eye movements • 409 eye movements: saccades and pursuits