1. Department of Neurosurgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA;
2. Center for Neurological Restoration, Cleveland Clinic, Cleveland, OH, USA;
3. Department of Orthopedics and Rehabilitation, University of Iowa Hospitals and Clinics, Iowa City, IA, USA;
4. Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, USA