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SummaryWe propose a unified explanation for the diverse distortions in time-averaged activity of grid and place cells observed after environmental deformations. In our account, input from border cells resets the spatial phase but not the spatial scale of grid cells, maintaining learned relationships between grid phase and environmental boundaries. A computational model implementing this mechanism reproduced several commonly observed experimental effects, including scaledependent distortions in time-averaged grid fields after environmental deformation, and stretched, duplicated, and fractured place fields. Furthermore, this model predicted a striking new effect: dynamic, history-dependent 'shifts' in grid phase. We reanalyzed two classic datasets on grid rescaling and found clear evidence for such shifts, which have not previously been reported. These results invite a reconceptualization of the effects of environmental deformations on spatial representations -rather than rescaling the spatial metric of the cognitive map, as previously believed, alterations in environmental geometric may dynamically shift the map..
CC-BY-NC-ND 4.0 International license peer-reviewed) is the author/funder. It is made available under aThe copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/174367 doi: bioRxiv preprint first posted online Aug. 10, 2017; 3 The cognitive map is thought to be a metric representation of space that preserves distances between represented locations [1,2]. Entorhinal grid cells are hypothesized to generate this metric by maintaining an internally-generated, path-integrated representation of space [3][4][5][6][7][8]. Results of environmental deformation experiments have led to the belief that this metric is fundamentally malleable [9][10][11]. In these experiments, neural activity is recorded as a rat explores deformed versions of a familiar environment where chamber walls have been stretched, compressed, removed, or inserted. Such deformations induce a number of distortions in the time-averaged activity of both grid [9,11] and hippocampal place cells [12][13][14][15][16]. Often described as 'rescaling', these distortions have been taken to suggest that the spatial metric of the cognitive map can be reshaped by altering environmental geometry [9,17,18]. Crucially, however, this interpretation assumes that the distortions observed in the time-averaged rate maps of these cells directly reflect corresponding changes to the underlying spatial code. Here, we propose and test an alternative mechanism which challenges this interpretation and instead indicates that during environmental deformations the grid cell spatial metric does not rescale, but instead undergoes dynamical, history-dependent phase shifts.We hypothesize, as others have [10,[19][20][21][22][23], that border cells interact with grid cells in familiar environments to maintain learned relationships between grid phase and boundaries. Here we further propose that the same mechanism is responsible for inducing diverse and u...