(a) Left: Vector map for all cells in one rat. Vectors indicate field translocation and point from the original field position in A or B to the nearest field in AB within 60% of the cell’s grid spacing in A, B, and AB. Number of cells is indicated at the bottom right. Center: Distribution plots show translation vectors (in black) for blocks of 50 x 50 cm of the recording box. Mean resultant vectors (MVL) are added on top of the single vectors as thick red lines. Grey background shading indicates MVL P<0.001 with Rayleigh test for uniformity. Right: Average sliding cross-correlation heat map for the cells to the left, color coded from dark blue to dark red (color bar). Shifts were normalized to each cell’s average grid spacing in A, B, and AB (1 bin = 2 cm). (b)- (f) Further examples from other rats, displayed as in a. (g) As in a-f but the vector map is for all vectors from all cells and rats (n = 128, 10 rats). To compute average local field displacement, vectors were sorted into square windows of side length 16 cm and averaged (see Fig. 2c). (h) The displacement of firing fields in the centre of the box was accompanied by a change in peak firing rates of grid fields that could be matched before and after removal of the wall. The scatterplot shows that, after the wall was removed, the peak firing rate of grid fields in the central 10th percentile bands increased from 3.91 ± 0.15 Hz in A|B to 4.70 ± 0.18Hz in AB (t(548) = −3.32, P = 9.5 x 10−4, two-sided Student’s t-test; peak rate defined as the rate in the central bin of the grid field). In the distal 10th percentile bands, there was no significant change in firing rates (before: 3.61 ± 0.12 Hz; after: 3.44 ± 0.12 Hz; t(692) = 0.92, P = 0.35, two-sided Student’s t-test).