Control of Human Arm Movements

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The focus of my research program is to study the organization of central control signals for voluntary limb movement, and the neural, cognitive and sensory mechanisms underlying motor learning and sensory-motor adaptation. A combination of empirical and modelling studies are used to test hypotheses about how multi-joint limb movements are controlled and how motor learning is achieved. The studies outlined in this proposal are organized in two major themes: (1) Sensory changes (somatosensory and visual) that accompany learning to interact with objects. Our previous studies document how both somatosensory acuity (sensitivity to changes in hand position) and bias (sensed position of the hand) are modulated when learning to reach in the presence of novel forces. Here, we propose to extend this work in a novel direction by studying how both somatosensory and visual acuity and bias are modulated when learning to interact with objects in the environment, both targets and obstacles. (2) We propose a novel set of studies that take advantage of a new 3-DOF robotic exoskeleton, to test models of how multi-joint arm movements are planned and controlled. The new IMT2 exoskeleton robot (funded by an NSERC RTI award to the applicant) is unique in the world, in that it allows for fully instrumented, and controlled, motion in shoulder, elbow AND wrist joints, in a horizontal plane. The new robot will allow us to directly test models of movement planning and control (e.g. the Uncontrolled Manifold theory, the Minimal Intervention model, Optimal Control models, etc), by capitalizing on the kinematic redundancy in the shoulder/elbow/wrist system in the horizontal plane. For example we will be able to perturb limb movements at the joint level while keeping the endpoint position unperturbed, thereby allowing us to study what variables are controlled during movement. Similar approaches will allow us to study how the system responds to noise and variability injected at different joints, or combinations of joints, and how these responses change over the course of motor learning. The results of this research will add significantly to our knowledge of how voluntary movements are planned and controlled, and how motor and sensory systems interact.