1. SFVA Medical Center, San Francisco, California, USA;
2. Neurology Service, SFVA Medical Center, University of California, San Francisco, California, USA;
3. VA Northern California Health Care System, University of California, San Francisco, CA, USA;
4. SFVA Medical Center, San Francisco, CA, USA;
5. University of California Berkeley, Helen Wills Neuroscience Institute, Berkeley CA, USA;
6. SFVA Medical Center, University of California, San Francisco, CA, USA