Abstract
When reaching to a visual target, humans need to transform the spatial target representation into the coordinate system of their moving arm. It has been shown that increased demands in such coordinate transformations, for instance when the head is rolled toward one shoulder, lead to higher movement variability and influence movement decisions. However, it is unknown whether the brain incorporates such added variability to adjust movements when it is necessary. We designed an obstacle avoidance task in which participants had to reach to a visual target without colliding with an obstacle. We introduced different coordinate transformation demands by varying head roll (straight, 30° clockwise and 30° counterclockwise). In agreement with previous studies, we observed that the reaching variability increased when the head was tilted. In addition, participants systematically changed their obstacle avoidance behavior with head roll. In particular, they changed the preferred direction of passing the obstacle and increased the error margins indicated by stronger movement curvature. Indeed, participants’ reaching movements did not differ in the number of collisions between the head roll and the head straight conditions. These results suggest that the brain takes the added movement variability during head roll into account and compensates for it by adjusting the reaching trajectories.
