1. From the Departments of Neurology and Anatomy & Neurobiology (J.D.R., V.L., L.D.-Y., J.S., S.C.C.), University of California, Irvine, CA; the Department of Medical Gerontology (J.M.N.), Trinity College, Dublin, UK; and the Sobell Department Motor Neuroscience & Movement Disorders (N.S.W.), UCL Institute of Neurology, Queen Square, London, UK.