1. PET Centre, Aarhus University Hospitals, Nørrebrogade 44, DK‐8000 Aarhus C, Denmark
2. Division of Neurophysiology, Department of Medical Physiology, the Panum Institute, University of Copenhagen, Blegdamsvej 3, DK‐2200 Copenhagen N, Denmark
3. Centre for Sensory‐Motor Interaction (SMI), Aalborg University, Fredrik Bajers Vej 7D‐3, DK‐9220 Aalborg, Denmark