(a) Representative firing rate maps for 6 border cells from 3 rats for the divided A|B environment and the merged AB environment. Peak firing rates are indicated at the bottom right. Rat identity and cell number is indicated at the top (T = tetrode, C = cell). Scale bar, 50 cm. (b) As in a but for 7 non-periodic spatially modulated cells from 3 rats in A|B and AB. Scale bar, 50 cm. These cells had high spatial information content and stable firing locations (spatial information value of 0.82 ± 0.05 and spatial correlation between first and second half of trial of 0.49 ± 0.03; all trials and all parts of environment, mean ± s.e.m). (c) Polar plots of angular firing rate distribution for 10 representative head direction cells from 3 rats in A, B, and AB. Rat number and trial date are indicated at the top. Cell number is indicated at the left site (T = tetrode, C = cell). Mean resultant vector length, a measure for directional tuning, is indicated at the top in each plot. Peak firing rate is indicated at the bottom right.