1. K. Hsiao and S. Nilsen, Department of Neurology, UMHC Box 295, 420 Delaware Street, University of Minnesota, Minneapolis, MN 55455, USA.
2. P. Chapman, Physiology Unit, University of Wales, Cardiff CF1 3US, UK.
3. C. Eckman, Y. Harigaya, S. Younkin, Mayo Clinic Jacksonville, Jacksonville, FL 32224, USA.
4. F. Yang and G. Cole, GRECC, Veterans Administration Medical Center, Sepulveda, CA 91343, USA, and Departments of Medicine and Neurology, University of California, Los Angeles, CA 91343, USA.