1Neuroimaging Research Unit, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy, 2Clinic of Neurology, Faculty of Medicine, University of Belgrade, Belgrade, Yugoslavia, 3Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, Netherlands, 4Department of Neurology, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy