1. From the Department of Neurology (A.T.), University of Southern California, Los Angeles, CA; the Department of Neurology (A.T.), Rancho Los Amigos National Rehabilitation Center, Downey, CA; the Department of Biomathematics (D.M.), University of California at Los Angeles, Los Angeles, CA; and the Department of Neurology (B.O.), University of California at San Diego, San Diego, CA.