1. Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston (M.E.G., E.G.).
2. Division of Clinical Research, NINDS, Bethesda, MD (C.B.W., S.J.).
3. Department of Clinical Neurosciences, University of Calgary, Alberta, Canada (E.E.S.).
4. Helmsley Trust Electrophysiology Center, Icahn School of Medicine at Mount Sinai, New York (V.Y.R.).
5. Department of Neurology, Georgetown University Medical Center (J.G.M.).
6. Department of Cardiology, University of California, San Diego, La Jolla (J.C.H.).