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Genela Morris

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2 papers

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NeurIPS Conference 2025 Conference Paper

REMI: Reconstructing Episodic Memory During Internally Driven Path Planning

Zhaoze Wang
Genela Morris
Dori Derdikman
Pratik Chaudhari
Vijay Balasubramanian

Grid cells in the medial entorhinal cortex (MEC) and place cells in the hippocampus (HC) both form spatial representations. Grid cells fire in triangular grid patterns, while place cells fire at specific locations and respond to contextual cues. How do these interacting systems support not only spatial encoding but also internally driven path planning, such as navigating to locations recalled from cues? Here, we propose a system-level theory of MEC-HC wiring that explains how grid and place cell patterns could be connected to enable cue-triggered goal retrieval, path planning, and reconstruction of sensory experience along planned routes. We suggest that place cells autoassociate sensory inputs with grid cell patterns, allowing sensory cues to trigger recall of goal-location grid patterns. We show analytically that grid-based planning permits shortcuts through unvisited locations and generalizes local transitions to long-range paths. During planning, intermediate grid states trigger place cell pattern completion, reconstructing sensory experiences along the route. Using a single-layer RNN modeling the HC-MEC loop with a planning subnetwork, we demonstrate these effects in both biologically grounded navigation simulations using RatatouGym and visually realistic navigation tasks using Habitat Sim.

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RLDM Conference 2013 Conference Abstract

The hippocampal cognitive map is rearranged to represent reinforcement relevant dimensions

Genela Morris
Tugba Ozdogan

Adaptive behavior requires correct identification and efficient representation of the multiple in- puts available at any given moment. The representation method will determine efficiency of learning, and, importantly, generalization ability. However, different learning problems call for different representations of the same input. Here we focus on parameter coding by hippocampal primary neurons. We recorded the activity of hippocampal primary neurons in a specially devised olfactory space, in which rats foraged for reward based solely on olfactory cues and studied the dependence of the activity of these neurons on the ”state’ assumed by the animal, as derived from behavioral parameters. We show that classical place-cells perform superb encoding of olfactory space, when this is the only reference frame that is relevant for re- ward collection. Furthermore, the same cells shifted their firing fields from room coordinates to olfactory coordinates as animals learned to rely on them in order to obtain reward.

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