Fig. 3.

Serial activation of a dual-controller system describes differences in movement. Simulations of reaching movements show that 2 poorly tuned controllers can predict deafferented patient’s (GL’s) behavior. Hand paths and velocity profiles (insets) are shown for simulations of right arm movements involving pure trajectory control (A), pure postural control in a system with low joint damping (B), activation of the postural controller at peak velocity (C), late activation of postural control in a system with typical joint stiffness and damping values (E), and early (D) and late (F) activation of postural control in a system with joint stiffness and damping values similar to GL’s. Scale bars for trajectories = 2-cm simulated hand movement. Scale bars for velocity profiles represent 0.5 m/s.