a–d, CA1 recordings. Cells that are qualified as place cells (spatial selectivity index>0.3, peak firing rate>1 Hz) in either environment are included in this analysis (n = 283 cells). Cells are pooled from 4 recording sessions, 3 animals. (a) Normalized firing rates of cells sorted by the center of mass (COM) of each cell’s firing activity on the oval track (left). Normalized firing rates of cells with the same ranking (based on oval track activities) on the triangle track (right). (b) Distances of firing activity COM (ΔCOM) between pairs of cells, sorted in the same way as in (a). As expected from the sorting method, ΔCOM has small values along the diagonal of the pairwise matrix on the oval track (left). However, this diagonal pattern disappears on the triangle track (right). (c) ΔCOM on the triangle track was plotted against that on the oval track (blue, mean±s.e.m.). The black line is the averaged ΔCOM on the triangle track. ΔCOM (oval) was binned with 5 cm. ΔCOM on the triangle track shows a nearly flat line around the averaged value. There is a slight trend that pairs with smaller ΔCOM on the oval track tend to have smaller ΔCOM on the triangle track, indicating some maintained topological structures. However, this effect is very weak as the maximal distance between the observed ΔCOM (triangle) is just around 0.1×S.D. from the mean (shown as z-score in d). (d) Z-scores of ΔCOM (triangle) at each bin, compared with the mean value of all ΔCOM (triangle) (the black line in c). e–h, The same as in (a–d) with CA3 recordings (n = 243 cells). Cells are pooled from 3 recording sessions, 3 animals.