1. a Jacobs Center for Lifelong Learning and Institutional Development, International University Bremen , Bremen, Germany E-mail:
2. b School of Psychology, Georgia Institute of Technology , Atlanta, Georgia, USA
3. c Department of Biomedical Engineering , Center for Neurological Restoration, The Cleveland Clinic , Cleveland, Ohio, USA
4. d Center for Functional Electrical Stimulation, Louis Stokes VAMC , Cleveland, Ohio, USA