Howard Hughes Medical Institute, Computational Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America, Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University of Science and Technology, MTFS, Trondheim, Norway.|Howard Hughes Medical Institute, Computational Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America, Department of Physics, University of California at San Diego, La Jolla, California, United States of America.|Howard Hughes Medical Institute, Computational Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America, Division of Biological Sciences, University of California at San Diego, La Jolla, California, United States of America.