1. Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY 40202, USA
2. Department of Bioengineering, University of Louisville, Louisville, KY 40292, USA
3. Department of Neurological Surgery, University of Louisville, Louisville, KY 40202, USA
4. Department of Medicine, University of Udine, 33100 Udine, Italy
5. Frazier Rehabilitation Institute, University of Louisville Health, Louisville, KY 40202, USA