1. Department of Pediatrics, Stanford University School of Medicine, Stanford, California 94305-5119;
2. Program in Human Biology, Stanford University, Stanford, California 94305-2160;
3. Brain Research Institute, Universty of California, Los Angeles, California 90095;
4. National Aeronautics and Space Administration Ames Research Center, Moffett Field, California 94035-1000; and
5. Department of Mechanical Engineering, Stanford University, Stanford, California 94305-3030