1 Human Motor Control Section, Medical Neurology Branch, National Institute on Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States.
2 Department of Neuroscience, Imaging and Clinical Sciences, G. D'Annunzio University, Chieti, Italy.
3 Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States.