1. T. H. Bullock is at the Scripps Institution of Oceanography and Department of Neuroscience, University of California, San Diego, La Jolla, CA 92093, USA.
2. M. V. L. Bennett is in the Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
3. D. Johnston is at the Center for Learning and Memory, University of Texas, Austin, TX 78712, USA.
4. R. Josephson is in the Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA.
5. E. Marder is in the Department of Biology, Brandeis University, Waltham, MA 02454, USA.
6. R. D. Fields is in the Nervous Systems Development and Plasticity Section, National Institute of Child Health and Human Development, Bethesda, MD 20892, USA.