1. Institute for Empirical Research in Economics, University of Zurich, Blümlisalpstrasse 10, 8006 Zurich, Switzerland.
2. Department of Neurology, University Hospital Zurich, Switzerland.
3. Collegium Helveticum, Schmelzbergstrasse 25, 8092 Zurich, Switzerland.
4. Center for Noninvasive Brain Stimulation, Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA 02115, USA.
5. PET Center, Nuclear Medicine, Department of Radiology, University Hospital, 8091 Zurich, Switzerland.