Inverse motorische modelle bei kindern und erwachsenen: Die rolle des visuellen feedbacks

Neurobiological evidence reveals that neurally coded inverse models of limb dynamics form the basis for feed-forward motor control in humans. This study investigates the role of visual feedback for the acquisition of inverse motor models in children and adults. Eight 9-year-old and eight 5-year-old children and eight adults performed goal-directed horizontal forearm movements using a single-joint arm manipulandum. When visual feedback was not available before and after movement execution (partial feedback), spatial error increased in adults and children. However, the lack of visual information during movement execution did not affect adult motor performance. In contrast, spatial error increased in both children groups when visual feedback was removed. Spatial accuracy was improved during the partial feedback condition, if children had prior practice under full visual feedback. The increased dependence on visual feedback, especially in the younger children, is a sign that children relied predominantly on central feedback mechanisms for motor control, because their feed-forward control was not yet functional. The reasons for the lack of feed-forward control are twofold: First, there are problems in motor planning, specifically with the inverse kinematic transformation (from hand position to joint angles). Second, there are deficits in the neural controller, specifically due to imprecise neural estimations of the true limb dynamics.