Talk Title: High-capacity flexible hippocampal associative and episodic memory enabled by prestructured "spatial'' representations

Abstract

Hippocampal circuits in the brain enable two distinct cognitive functions: the construction of spatial maps for navigation and the storage of sequential episodic memories. This dual role remains an enduring enigma. While there have been significant advances in modeling spatial representations in the hippocampus, we lack good models of its role in episodic memory. Additionally, we now know that the spatial codes in grid and hippocampal cells generalize to represent non-spatial cognitive domains, but it is unclear why this arrangement might be advantageous. In this talk, I’ll discuss a neocortical-entorhinal-hippocampal network model that implements a high-capacity and flexible general associative memory, spatial memory, and episodic memory based on a scaffold of rigid, low-dimensional dynamics in grid cells and fixed random projections to the hippocampus. The circuit factorizes the problem of content storage from the problem of generating error-correcting stable states. Unlike existing neural memory models, which exhibit a memory cliff, the circuit exhibits a graceful tradeoff between the number of stored items and detail. The scaffold is also critical for constructing episodic memory: it enables high-capacity sequence memory by simplifying the chaining problem into one of learning low-dimensional transitions. The model recapitulates a number of hippocampal physiology results, and interestingly provides a potential explanation for the striking efficacy of the ``memory palaces'' technique of memory athletes.

Brief Bio

Ila Fiete is a Professor in the Department of Brain and Cognitive Sciences and an Associate Member of the McGovern Institute at MIT. She obtained her undergraduate degrees in Physics and Mathematics at the University of Michigan and her M.A. and Ph.D. in Physics at Harvard, under the guidance of Sebastian Seung at MIT (co-advised by Daniel Fisher). Her postdoctoral work was at the Kavli Institute for Theoretical Physics at Santa Barbara, and at Caltech, where she was a Broad Fellow. She was subsequently on the faculty of the University of Texas at Austin in the Center for Learning and Memory. Ila Fiete is an HHMI Faculty Scholar. She has been a CIFAR Senior Fellow, a McKnight Scholar, an ONR Young Investigator, an Alfred P. Sloan Foundation Fellow and a Searle Scholar.