1. Heidelberg University Hospital, Spinal Cord Injury Center, Heidelberg, Germany
2. Karlsruhe Institute of Technology, Institute for Applied Computer Science/Automation Technology, Karlsruhe, Germany
3. Georg-August-University Göttingen, Department of Clinical Neurophysiology, Göttingen, Germany
4. Karlsruhe Institute of Technology, Institute for Applied Computer Science, Karlsruhe, Germany