[1] Univ So Calif, Dept Neurol, Los Angeles, CA USA
[2] Rancho Los Amigos Natl Rehabil Ctr, Dept Neurol, Downey, CA USA
[3] Med Univ S Carolina, Dept Neurol, Charleston, SC 29425 USA
[4] Univ Calif Los Angeles, Dept Biomath, Los Angeles, CA 90024 USA