Contribution of head-direction cells to path integration within grid cell networks
Final Report Abstract
This project investigates how grid cells in the brain support navigation when animals rely on internal cues rather than external landmarks—a process known as path integration. Grid cells are specialized neurons in the entorhinal cortex that typically generate strikingly regular, hexagonal patterns of activity thought to serve as an internal coordinate system. While this system is well-characterized in animals exploring open environments, its role in goal-directed navigation tasks remained unclear. Our experiments revealed three key findings that challenge the classical view of grid cells as a globally stable spatial map. First, during a homing task that required mice to navigate using self-motion cues alone, we observed a substantial reduction in the regular, grid-like activity pattern. This was unexpected and suggests that grid cells reorganize their activity when animals are engaged in goal-directed behavior rather than random exploration. Second, we discovered that grid cells dynamically re-anchor their firing patterns to behaviorally relevant landmarks—in this case, a lever the animal had to find. The internal map effectively "moved" with the task-relevant object, even though that object changed position from trial to trial. Third, we found that subtle changes in the orientation of the grid pattern during the task were predictive of the animal’s return path, suggesting that grid orientation—rather than absolute position—plays a critical role in guiding navigation. A surprising aspect of the project was how flexible the grid system turned out to be. Rather than acting as a rigid GPS-like map, grid cells demonstrated a capacity to operate in multiple, overlapping reference frames. This flexibility may help explain how animals—and potentially humans—can navigate reliably in complex or changing environments. Our findings contribute to a revised understanding of spatial coding in the brain and suggest that grid cells are not just passive reflectors of movement but actively adapt their reference frames to task demands. These insights have potential implications for the design of artificial navigation systems, and may also help us better understand disorientation symptoms in neurodegenerative diseases like Alzheimer’s. The discovery that grid cell maps can dynamically re-anchor to goal locations may prove to be a compelling example for illustrating brain flexibility in popular science communications.
Publications
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Hippocampal firing fields anchored to a moving object predict homing direction during path-integration-based behavior. Nature Communications, 14(1).
Najafian Jazi, Maryam; Tymorek, Adrian; Yen, Ting-Yun; Jose Kavarayil, Felix; Stingl, Moritz; Chau, Sherman Richard; Baskurt, Benay; García Vilela, Celia & Allen, Kevin
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Grid cells accurately track movement during path integration-based navigation despite switching reference frames. Nature Neuroscience, 28(10), 2092-2105.
Peng, Jing-Jie; Throm, Beate; Najafian Jazi, Maryam; Yen, Ting-Yun; Pizzarelli, Rocco; Monyer, Hannah & Allen, Kevin
