[1] Stanford Univ, Sch Med, Dept Neurol & Neurol Sci, Stanford, CA 94305 USA
[2] Univ Calif San Diego, Dept Neurosci, La Jolla, CA 92093 USA
[3] Univ Calif San Diego, Dept Pathol, La Jolla, CA 92093 USA
[4] GRECC, VA Palo Alto Hlth Care Syst, Palo Alto, CA 94304 USA