Supported in part by the Office of Naval Research (Cognitive and Neural Sciences, N00014-93-1-0130), the National Eye Institute (EY09669), a UNC-CH Junior Faculty Development Award, an ORAU Junior Faculty Enhancement Award from Oak Ridge Associated Universities, the University of Minnesota Center for Research in Learning, Perception, and Cognition, the National Institute of Child Health and Human Development (HD-07151), and the Minnesota Supercomputer Institute.
We thank Stephen Aylward, Eliza Graves, Robert Hubbard, and Al Nigrin for many valuable discussions.