1. From the Departments of Neurology (L.D.A., P.A.W., N.L.H.-C.), Biostatistics (L.D.A., J.M.M., A.B.), and Mathematics and Statistics (R.B.D.), Boston University School of Medicine, Boston, Mass; and the Department of Neurology and Center for Neuroscience (C.D.), University of California at Davis, Sacramento, Calif.