Extended Data Fig. 6: Dynamics of recalibration.

a–e, The complete hippocampal gain (H) dynamics for all five rats for sessions that exhibited landmark control. The gain dynamics for rat 692 is also shown in the main text (Fig. 3e). In the left panels for each rat (colour), H is plotted as a function of laps run in the laboratory frame. Sessions are aligned to the instant when the landmarks were turned off (denoted as lap 0). In the presence of landmarks (before lap 0), the hippocampal gain tracked the experimental-gain profiles during a given session (not shown). After the landmarks were turned off, the traces largely maintained their recalibrated gain, while also showing some variable drift across sessions. Note that for each rat, for sessions in which G = 1 (that is, the landmarks did not move), the value of H was close to 1 when the landmarks were turned off. The right panels for each rat show the gain trajectories of all the units in the dataset. The grey scale represents the number of active cells with gains falling in a given bin (bin size is 5° for laps axis and 0.01 for gain axis). These graphs demonstrate the high degree of coherence of the hippocampal population, as almost all cells shared the same gain with minimal deviation. The light-coloured lines that occasionally deviate from the main trajectories arise from the small number of cells with poor spatial tuning or from cells that remapped. In the latter case, because our spectral gain analysis used a window of 12 laps, these remapped cells continued to show artefactual values for the limited number of laps that fall in this window but during which the cell was silent. As can be seen, these exceptions had negligible influence on the median population gain values. f, Sustained recalibration. Comparison of G_final (x axis) and H computed using laps 13–24 (that is, the value of H at lap 18) after the landmarks were turned off (y axis). Sessions for each rat are plotted in different colours, along with the perfect recalibration line (dashed line, black) and a linear fit (solid line, black; n = 27 sessions, Pearson’s r₂₅ = 0.85, P = 2.04 × 10⁻⁸). The number of data points is lower than in Fig. 3c because some sessions ended before lap 24. g, Histogram of coherence scores (same format as Fig. 2g) for units firing during epoch 4 (landmarks off). The shape of the histogram is very similar to that of Fig. 2g. Almost all units had a coherence score of less than 0.1, indicating that the place fields acted as a coherent population in sessions with (blue) and without (pink) landmark control in epochs 1–3, even after the landmarks were turned off. Units with a coherence score of greater than 0.1 (range 0.11–0.41) were combined in a single bin (17/336 units).