Movement Neuroscience Laboratory

Address: 27 Rec Hall, University Park, PA 16802 Phone: 814-865-7938 email: rls45@psu.edu

The research in the movement neuroscience and neurorehabilitation laboratories is fundamentally translational. Studies in typical adults, across the lifespan, are conducted primarily in the movement neuroscience laboratory. The major themes of this research include: 1) The relative contributions of visual and proprioceptive information to planning and control of movements, and 2) Lateralization of motor control. Empirical studies in proprioceptively deafferented patients, as well as studies that dissociate visual and proprioceptive information are done using our virtual reality and movement tracking system, Kinereach. This system was custom designed and programmed by Dr. Sainburg, and has been progressively expanded, since its inception in 1999.

An example of such an experiment is the visuomotor rotation task shown in the movie below, in which the cursor is directed 30° counterclockwise relative to the start position from the hand. The participant only sees the motion of the cursor and slowly adapts to the visuomotor distortion through largely implicit mechanisms. Following learning, the rotation is removed and veridical conditions are restored. The participant then directs the hand motion clockwise to the target, persisting in the previously learned pattern, reflecting a phenomenon called “aftereffects”.

Other empirical experiments designed to understand how individuals respond to proprioceptive and visual perturbations to make movement corrections include studies that impose a target jump. In these experiments, the target is ‘jumped’ to a new location upon movement start. As can be seen in the movie below, the participant responds to this ‘jump’ with muscle electrical activity (EMG) that is initiated about 200 milliseconds (1/5 of a second) after the target jump. In this movie, the baseline movement (without the target jump) is shown in white profiles for elbow displacement (lower right), elbow torque (upper right) and EMG (lower left). The yellow shows the trial when the target is jumped at movement onset. The hand movement can be seen as the cursor (yellow circle) moving toward the target.

Another method employed in our laboratory is to conduct dynamic simulations. In the movie below, a multiple joint reaching movement is made by a participant. The components of elbow joint torque are shown at the top left of the figure. The green profile is interaction torque, produced at the forearm by motion of the upper arm. The simulation is the second movement, in which the muscle torque components that account for the interaction torque are removed, thus demonstrating a movement that does not account for interaction torques in its control algorithm. Interestingly this movement is very similar to the movements made by proprioceptively deafferented patients, suggesting that proprioception is critical to predict intersegmental dynamics.