Episodic Memory and Spatial Navigation in the Medial Temporal Lobe

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• Dr David E Huber - Department of Psychological and Brain Sciences University of Massachusetts, Amherst
• Tuesday 30 June 2015, 13:00-14:00
• Kenneth Craik Room, Craik Marshall Building, Downing Site, Cambridge.

If you have a question about this talk, please contact Lorraine Coulson.

Hippocampal place cells and entorhinal grid cells are abundant, suggesting that the medial temporal lobe (MTL) primarily supports spatial navigation. At the same time, neuropsychological studies find that the MTL supports the formation of episodic memories. We explain this seeming contradiction with a hierarchical memory model in which episodic memories are points in a high dimensional space. Because the X/Y dimensions used to analyze place and grid cells are part of this representation, different levels of the hierarchy give the appearance of place and grid cells when only analyzed in terms of the X/Y plane. We propose that X/Y position information is provided by border cells, which is combined with the true attributes of grid cells (e.g., something other than X/Y, such as temperature, surface texture, time of day, etc.) to produce cognitive maps and ultimately multidimensional episodic memories in the hippocampus. Place cell responses are retrieved memory responses that occur when the animal is in a position sufficiently close to the location of a prior experience. Memory consolidation separates memories in the multidimensional space, producing a hexagonal array of place cells. The response of a cell representing a non-spatial attribute common to the entire set of memories is hexagonal in the X/Y plane owing to excitatory feedback from each place cell. Thus, rather building place cells out of grid cells, as proposed by other models, our account builds grid cells out of place cells. Furthermore, our account proposes that place cells are episodic memories and grid cells are non-spatial.

This talk is part of the Behavioural and Clinical Neuroscience Seminars series.

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