1. From the Departments of Neurology (C.B.W., R.L.S.), Biostatistics (M.C.P), Radiology and Biomedical Engineering (T.R.B.), and the Sergievsky Center (R.L.S.), Columbia University College of Physicians and Surgeons and the Mailman School of Public Health, New York, NY; the Department of Medicine (S.P.S., R.H.A.), School of Medicine, University of Colorado, Denver, Colo; and the Department of Neurology and Center for Neuroscience (C.D.), University of California-Davis, Sacramento, Calif.