Wim Vanduffel1,2,3. 1. Laboratory of Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven, Leuven, 3000, Belgium; wim@nmr.mgh.harvard.edu. 2. Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129. 3. Department of Radiology, Harvard Medical School, Boston, MA 02144.