Neuromuscular Research Laboratory
Director: V. Reggie Edgerton

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Dr. V. Reggie Edgerton received his Ph.D. in Exercise Physiology from Michigan State University, Masters from University of Iowa and BS from East Carolina University. He has been a Professor at the University of California, Los Angeles, since 1968. Dr. Edgerton’s laboratory focuses on two main research questions. One question is how do the neural networks in the lumbar spinal cord of mammals, including humans, regain control of standing, stepping and voluntary control of fine movements after paralysis, and how can these motor functions be modified by chronically imposing activity-dependent interventions after spinal cord injury. Limb motion, electromyographic and kinetics data are recorded to assess the quality of movements. These studies have shown that the mammalian spinal cord, without any input from the brain, can learn specific complex motor tasks such as standing and stepping. We have recently observed that electrodes placed epidurally over the lumbosacral spinal cord can be used to neuromodulate the spinal circuitry so that after a complete spinal cord transection, when used in combination with select pharmacological compounds, the rat is capable of performing full weightbearing stepping at different speeds and at different levels of load bearing and can even step in different directions. Thus we now have 3 effective ways to neuromodulate the spinal cord to improve and regain function: tonic stimulation of the spinal circuitry using epidural electrodes, pharmacological compounds and repetitive training of motor tasks. Application of these interventions has made it possible to recover full weightbearing standing and stepping after complete paralysis in the rat. Even more recent experimental data have shown that epidural stimulation alone can enable individuals with complete paralysis for more than 2 years can regain the ability to stand independently and even regain significant levels of voluntary control of movement of the legs. Largely using animal models of complete paralysis we are aggressively developing and testing these interventions in humans, as we are also attempting to determine the mechanisms for this recovery potential.

In conjunction with these efforts we are also focused on technological developments that can facilitate the application of the different methods of neuromodulation of the spinal circuitry. For example, we are developing robotic devices to facilitate assessment and motor training, complex electrode arrays for better control of spinal stimulation, a more sophisticated stimulation device to improve fine control and to have this device under the control of the user and in real-time. In concert with these efforts, considerable focus is directed toward integrating neural models of locomotion with actual musculoskeletal properties that are subject specific. Using magnetic resonance imaging we have developed unique methods to observe detailed movements of muscle fibers and muscle fascicles in vivo in human subjects voluntarily performing a specific motor task. Part of our effort also is to determine to what extent, does the nervous system control the quantity and quality of protein expression in skeletal muscle fibers? What are the electrical, mechanical and humeral factors that determine the size of muscle fibers and their physiological properties.. Light and confocal microscopy including quantitative enzyme analyses and immunofluorescence microscopy are some of the experimental methods used to study motor unit plasticity. The principal animal models used are spinal cord injury, spaceflight and surgically induced compensatory hypertrophy. These studies have shown that although the nervous system has a significant influence on the kind and amount of specific proteins synthesized, there are factors intrinsic to individual fibers that also define these properties. The results show also that the neural influence that is associated with muscle fiber types is probably not mediated via the amount or pattern of activity of the motor units.

We are beginning to find that the interventions being studied for improving function after spinal cord injury are likely to have beneficial effects also on other neuromotor disorders such as stroke and Parkinson's. Experiments are being performed to test these possibilities. Finally, the different methods for neuromodulation of the spinal circuitry are also being tested with respect to their efficacy in improving function of the arms and hands.

All of these projects are being performed with national and international collaborators. Some of the principal universities and institutions are Caltech, University of Louisville, University of California at San Diego, Irvine, Davis and San Francisco, and the University of Puerto Rico.