The brain is a computer. In order to understand its function, we need to address computational questions of representation and algorithm. In a remarkable experiment, Barnes et al. (1997) found that when allowed two experiences in an environment, young animals used the same representation for both, but old animals sometimes used the same and sometimes used radically different representations, as if they were sometimes lost. I will use this result as an entry point into the question of how animals navigate through the world, and in particular the role of the hippocampus (a brain structure) in navigation. In the first part of my talk, I will synthesize a theory of rodent navigation, compatible with data at a variety of levels of description, including anatomical, behavioral, neurophysiological, and neuropharmacological. I will concentrate this discussion on the role of the hippocampus in navigation, concluding that it allows an animal to self-localize, to reset an internal coordinate system from external cues. In the second part of my talk, I will present experimental work which follows this hypothesis. We have developed a task which forces an animal to self-localize in order to receive reward. I will show that we can determine in which coordinate system the hippocampus is representing space at each moment in time, and that at a specific moment, the representation transitions from one coordinate system to another. This permits us to examine the role of this self-localization process in behavior.

SPEAKER BIO
David Redish received his BS in Computer Science from The Johns Hopkins Univerity in 1991 and his MS and PhD in Computer Science from Carnegie Mellon University in 1995 and 1997, respectively. His thesis, Beyond the Cognitive Map: Contributions to a Computational Theory of Rodent Navigation was completed under the guidance of his advisor, David Touretzky. Redish has been a Post-doc at the University of Arizona since October 1997, working with Dr. C.A. Barnes.

Dr. Redish is the recipient of several awards, including a NIH National Research Service Award (NRSA) 1997-2000; a National Science Foundation Fellowship, 1991-1993; and an IBM Outstanding Achievement Award, 1991. He is the author of a new book, now in press, entitled Beyond the Cognitive Map: From Place Cells to Episodic Memory, MIT Press and contributed to numerous conference and journal articles. His work, Computing Goal Locations from Place Codes, appears in Symbolic Visual Learning by Katushi Ikeuchi and Manuela Veloso, editors (Oxford University Press); and Separating Hippocampal Maps, to appear in Spatial Functions of the Hippocampal Formation and the Parietal Cortex, edited by N. Burgess, K. Jeffery, and J. O'Keefe (Oxford University Press).

Dr. Redish is a member of the Society for Neuroscience, and participated actively in the programs at the Center for the Neural Basis of Congition (CNBC), including the Neural Processes in Cognition Graduate Training Program (1992-1997), the NPC Distinguished Colloquia Committee (1995-1997), and the NPC Brain Bag Committee (1996). He was the maintainer of the Cognitive Neuroscience sites on the Internet (1994-1997), an award winning site, and the CNBC Webmaster (1994-1997).

In his free time, he is an accomplished poet and playwright.

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