T Rudroff1, F Proessl2, J Kamholz3, L L Ponto4. 1. Department of Health and Human Physiology, University of Iowa, USA. Electronic address: thorsten-rudroff@uiowa.edu. 2. Department of Health and Exercise Science, Colorado State University, USA. 3. Department of Neurology, University of Iowa Hospitals and Clinics, USA. 4. Department of Radiology/PET Imaging Center, University of Iowa Hospitals and Clinics, USA.