1. Department of Neuropsychology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
2. Department of Neurology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
3. Department of Neurology, St. Elisabeth Hospital, Tilburg, the Netherlands.
4. Department of Neurology, Medisch Spectrum Twente Enschede, Enschede, the Netherlands.