A vestibular-derived internal model for task-dependent reaching
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To plan and control arm movements while the body is in motion the brain needs to compensate for inertial forces acting on the arm. Here we investigated, if vestibular information is used to adapt reach-planning by contributing to the formation of an internal model of the arm dynamics. Specifically, we were interested in tracking the development of such an internal model over time. In addition we examined whether vestibular-mediated reach-control is modulated by task-demands. A linear sled was used to passively move participants while they performed reaching movements. Participants learned an association between reaching direction and the direction of a simultaneous sideways body translation. Randomly scattered trials in which the expected body motion was omitted were used to probe learning and induce online corrections. Task-demand was manipulated by using narrow and wide reach-targets. Recorded hand-trajectories were analyzed for adaptation-effects in deviations perpendicular to the reach direction. The analysis of task-modulations on online corrections focused on differences in movement endpoints and durations. We observed an adaptation of hand trajectories during body motion as well as indications for aftereffects when body motion was omitted. Further, both reaches with and without body motion showed increased endpoint variability and shorter durations for wide compared to narrow targets. Our findings support previous research showing that vestibular information is used to adapt reaching movements during whole-body motion. The observed aftereffects suggest that this adaptation relies on the formation of an internal model. Lastly, our results corroborate previous findings showing task-dependent modulations of vestibular feedback gains.
Faculteit der Sociale Wetenschappen