1. Department of Neurosurgery, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
2. International Center for Spinal Cord Injury, Hugo W. Moser Research Institute at Kennedy Krieger, Baltimore, MD, USA
3. Department of Physical Medicine & Rehabilitation, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
4. Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA