Thesis available

[David Redish]

My PhD thesis is now available on the WWW:

	BEYOND THE COGNITIVE MAP:
		Contributions to a Computational Neuroscience Theory
		of Rodent Navigation

		A. David Redish

	http://www.cs.cmu.edu/~dredish/pub/thesis.ps.gz
	
The thesis is 452 pages (2.5M gzipped, 9.6M uncompressed).  In
addition to novel contributions (see below), the thesis includes a 100
page Experimental Review (Chapter 2), a 75 page Navigation overview, a
30 page overview of hippocampal theories, and over 500 references
which some might find useful.

I have appended the abstract for those interested.

	***** NO HARDCOPIES AVAILABLE ********

I am sorry, but I due to the size of the thesis, I cannot send
hardcopies.   

------------------------------------------------------
Dr. A. David Redish	Computer Science Department CMU
graduated (!) student	Center for the Neural Basis of Cognition (CNBC)
http://www.cs.cmu.edu/~dredish
------------------------------------------------------------

	BEYOND THE COGNITIVE MAP:
		Contributions to a Computational Neuroscience Theory
		of Rodent Navigation

		Ph.D Thesis
		A. David Redish
		Computer Science Department and 
			Center for the Neural Basis of Cognition
		Carnegie Mellon University

Rodent navigation is a unique domain for studying information
processing in the brain because there is a vast literature of
experimental results at many levels of description, including
anatomical, behavioral, neurophysiological, and neuropharmacological.
This literature provides many constraints on candidate 
theories.  This thesis presents contributions to a theory of how
rodents navigate as well as an overview of that theory and how it
relates to the experimental literature.

In the first half of the thesis, I present a review and overview of
the rodent navigation literature, both experimental and theoretical. 
The key claim of the theory is that navigation can be
divided into two categories: taxon/praxic navigation and
locale navigation (O'Keefe and Nadel, 1978), and that locale navigation can
be understood as an interaction between five subsystems:  local
view,  head direction, path integration,  place code,
and goal memory (Redish and Touretzky, 1997).  
I bring ideas together from the extensive work done on rodent
navigation over the last century to show how the interaction of these
systems forms a comprehensive, computational theory of navigation.
This comprehensive theory has implications for an understanding of the
role of the hippocampus, suggesting that it shows three different
modes: storage, recall, and replay.  

In the second half of the thesis, I show specific contributions to
this overall theory.

	I report a simulation of the head direction system
	that can track multiple head direction speeds accurately.  The
	simulations show that the theory implies that head direction
	tuning curves in the anterior thalamic nuclei should deform
	during rotations.  This observation has been confirmed
	experimentally by Blair et al. (1997).

	By examining the computational requirements and the anatomical
	data, I suggest that the anatomical locus of the path
	integrator is in a loop comprised of the subiculum, the
	parasubiculum, and the superficial entorhinal cortex.  This
	contrasts with other hypotheses of the anatomical locus of
	path integration (e.g. hippocampus, McNaughton et al., 1996)
	and predicts that the hippocampus should not be involved in
	path integration.  This prediction has been recently tested
	and confirmed by Alyan et al. (1997).

	I present simulations demonstrating the viability of the
	three-mode hippocampal proposal, including storage and recall
	of locations within single environments, with ambiguous
	inputs, and in multiple environments.

	I present simulations demonstrating the viability of the
	dual-role hippocampus (recall and replay), showing that the
	two modes can coexist within the hippocampus even though the
	two roles seem to require incompatible connection matrices.

In addition, I present simulations of specific experiments, including 

	a simulation of the recent result from Barnes et al. (1997),
	showing that the model produces a bimodality in the
	correlations of representations of an environment in animals
	with deficient LTP.  These simulations show that the
	Barnes et al. result does not necessarily imply that the
	intra-hippocampal connections are pre-wired to form separate
	charts as suggested by Samsonovich (1997).

	a simulation of Sharp et al.'s (1990) data
	on the interaction between entry point and external cues,
	showing the first simulations capable of replicating all the single
	place field conditions reported by Sharp et al.

	simulations of Cheng (1986) and Margules and Gallistel (1988)
	showing the importance of disorientation in self-localization.

	simulations of Morris (1981), showing that the model can
	replicate navigation in the water maze.

	simulations of Collett et al. (1986) and our own gerbil
	navigation results, showing that the model can replicate a
	number of reactions to different manipulations of landmark
	arrays.