As we move our eyes, new images are constantly presented to the brain, yet we perceive the world as remaining still. This perceptual stability is thought to depend on a convergence of visual signals and corollary discharges reflecting the generation of voluntary eye movements. Visual and motor signals together construct an internal representation of space that is constantly updated. The neural mechanisms underlying this process are beginning to be understood at the level of single neurons, through single-unit recording in monkeys. Dr. Colby's research goal is to extend these observations to humans. She will use functional magnetic-resonance imaging (fMRI) to examine activity in the human brain during spatial updating. She expects that multiple brain regions will be involved in updating of visual memory traces. The most exciting outcome of these imaging experiments will be the delineation of the complete set of brain regions involved in spatial memory and cognition. To accomplish this goal by single-unit recording alone would take several years. The promise of functional imaging is that activity throughout the brain can be observed simultaneously, allowing one to see the entire network in action. In accord with the goals of the POWRE program, this new research program will significantly enhance Dr. Colby's research capabilities by providing access to unique technological resources.
