1. Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, San Francisco, CA, USA.
2. Brain and Spinal Injury Center, University of California, San Francisco, San Francisco, CA, USA.
3. Department of Basic Sciences, Division of Biomedical Engineering Sciences, Loma Linda University, Loma Linda, CA, USA.
4. Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, USA.
5. Weill Institute for Neuroscience, University of California, San Francisco, San Francisco, CA, USA.
6. San Francisco Veterans Affairs Healthcare System, San Francisco, CA, USA.
7. Kavli Institute of Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, USA.