Supplementary Figure 6: Summing spike-time cross-correlations across ±50 ms rather than ±5 ms produces qualitatively similar results.
(a) Spike-time cross-correlation values were summed across time lags of ± 50 ms and averaged within each (ΔφX, ΔφY) bin. As in Fig. 4, data from RUN (left), REM (center), and NREM (right) show maximal spike-train cross-correlation values at low relative spatial phases (that is, high overlap of grid fields) and weaker spike train cross-correlation values at high relative spatial phases (that is, low overlap of grid fields). The plots were scaled by their peak value to compare across behaviors with different spike rates. Normalized cross-correlation coefficient values are plotted in color scale for ease of plot interpretation. (b) Spike-time cross correlations for MEC (left, n = 211 cell pairs) and CA1 (right, n = 78 cell pairs) were summed within ± 50 ms and compared to 1-dimensional spatial phase magnitude (MEC) or relative angular distance (CA1). Data are plotted as average ± SEM. As in Fig. 5, spike-time cross-correlations for all three behavioral states in MEC decrease as the magnitude of relative spatial phase increases. In CA1, conversely, spike-time cross-correlations decrease as the distance between place fields increases only during active waking behavior (that is, RUN), but not during sleep states (that is, REM and NREM).
