Visual-Motor Strategies During a Bilateral Visually-Guided Reaching Task in Typically-Developing Children

Abstract

Background. Bilateral coordination is developed in childhood and is critical for performing many everyday motor skills. Reaching is a fundamental component of many bilateral skills and may be performed either symmetrically to targets of the same distance and angle, or asymmetrically to targets requiring unique reaching trajectories. During a unilateral reach, vision is primarily directed to the end target. However, during a bilateral reach there is competition between end targets for visual resources. It is not well-characterized how children utilize visual-motor strategies during a bilateral reach. Objective. The goal of this study was to compare kinematic performance and gaze behavior between symmetrical and asymmetrical reaches in typically developing children ages 8-17 years old. Methods. Participants (n = 20) performed a bilateral visually-guided reaching task using the KINARM Exoskeleton robot with an integrated gaze tracker. Outcome metrics were designed to characterize the spatiotemporal performance of hand kinematics and gaze behavior. Results. Spatial error was high in asymmetrical reaches compared to symmetrical reaches, and for the non-dominant arm compared to the dominant arm. Regardless of target symmetry, arms were tightly coupled at movement onset but became desynchronized with a bias towards the dominant arm reaching movement offset first. The number of eye movements did not differ between symmetrical and asymmetrical trials. A directional bias for gaze was found towards the dominant end target. Conclusions. Despite greater error in asymmetrical reaches, a common gaze strategy may be used for both symmetrical and asymmetrical trials in which the number of eye movements does not change, and vision is primarily directed towards the dominant end target first and for a larger overall percentage of the trial.