toph Braun' and Niels Birbaumer" 'Institute of Medical Psychology and Behavioral Neurobiology. University of Tuebingen, 72074 Tuebingen, Germany, zInternational Max Planck Research School of Neural and Behavioral Sciences. 72074 TObingcn, Germany, "Department of Functional Imaging, Center for Diagnostic Radiology and Neuroradiology. Universit