1. Department of Neurological Surgery, University of California San Francisco (UCSF), San Francisco, CA 94143.
2. Department of Neurology, University of California San Francisco (UCSF), San Francisco, CA 94143.
3. Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA 94720.
4. Genzyme Corporation, 500 Kendall Street, Cambridge, MA 02142.