Environmental deformations dynamically shift the grid cell spatial metric

Environmental deformations induce stereotyped distortions in the time-averaged activity of grid and place cells. We hypothesized that these effects are partly driven by border cell inputs which reset the spatial phase of grid cells, maintaining learned relationships between grid phase and environmental boundaries without altering inherent grid scale. A computational model of this mechanism reproduced diverse distortions during deformations, including scale-dependent and local distortions of grid fields, and stretched, duplicated, and fractured place fields. This model predicted a striking new effect: dynamic, history-dependent, boundary-tethered shifts in grid phase during deformations. We reanalyzed two rodent grid cell rescaling datasets and found direct evidence of these shifts, which have not been previously reported and contribute to the appearance of rescaling. These results demonstrate that the grid representation of geometrically deformed environments is not fixed, but rather dynamically changes with the specific experience of the navigator.