My research concerns regulation of movement in normal and neurologically disordered human subjects. These studies are conducted at the Rehabilitation Institute of Chicago, and they are directed toward an understanding of skeletomotor reflex function in patients with disorders of muscle tone. A related research area concerns the physiological effects of spinal cord injury. Using electrophysiological, pharmacological and biomechanical techniques, we are studying the sources of altered motoneuronal and interneuronal responses in spinal segments below a partial or complete spinal cord transection. Here, our objectives are to identify the key transmitters and/or neuromodulators responsible for altered responses and to develop compounds that may counteract these abnormalities in human subjects.

Figure: Kinematic and dynamic performance of unconstrained and constrained movements for the upper extremity of a single subject. The results indicate that single and two joint movements of the arm are controlled quite similarly, since there is no evidence for feedback -mediated correction of muscle commands to accommodate the transition between the two movement types. This argues against any moment to moment control of limb trajectory using muscle afferent information.

Hidler JM, Rymer WZ. (2000) Limit cycle behavior in spasticity: analysis and evaluation. IEEE Trans. Biomed. Eng. 47:1565-1575.

Popescu FC, Rymer WZ. (2000) End points of planar reaching movements are disrupted by small force pulses: An evaluation of the hypothesis of equifinality. J. Neurophysiol. 84:2670-2679.

Scheidt RA, Reinkensmeyer DJ, Conditt MA, Rymer WZ, Mussa-Ivaldi FA. (2000) Persistence of motor adaptation during constrained, multi-joint, arm movements. J. Neurophysiol. 84:853-862.

Zhang LQ, Wang G, Nishida T, Xu D, Sliwa JA, Rymer WZ. (2000) Hyperactive tendon reflexes in spastic multiple sclerosis: measures and mechanisms of action. Arch. Phys. Med. Rehabil. 81:901-909.

Scheidt RA, Rymer WZ. (2000) Control strategies for the transition from multijoint to single-joint arm movements studied using a simple mechanical constraint. J. Neurophysiol. 83:1-12.

Reinkensmeyer DJ, Schmit BD, Rymer WZ. (1999) Mechatronic assessment of arm impairment after chronic brain injury. Technol. Health Care 7:431-435.