[1] Univ Calif Davis, Dept Neurol, Sacramento, CA 95817 USA
[2] Univ Calif Davis, Dept Publ Hlth Sci, Sacramento, CA 95817 USA
[3] Vet Affairs No Calif Hlth Care Syst, Martinez, CA USA
[4] Univ Calif San Francisco, Dept Neurol, San Francisco, CA 94143 USA