Supplementary Figure 7: Stability of spike rate coupling in MEC and CA1 cell pairs.

a: Same as Fig. 5a, with subsampled spike rates. Since mean spike rates are known to influence the magnitude of observed correlations³⁴, it is possible that differences in observed coupling stability could merely reflect differences in mean spike rate. To discount this possibility, we randomly subsampled each unit’s mean spike rate to 0.2 Hz during each 15-minute window of the first hour of SWS. β₀-values are compared between the first 15 (β_{0_0-15}) and last 15 minutes (β_{0_45-60}) of the first hour of SWS. Displayed r-values are for Spearman rank correlation. b: Stability of β₀ for different Gaussian kernel widths, for intramodular grid–grid, HD–HD and CA1–CA1 cell pairs, calculated as the correlation between the cell pairs’ β_{0_0-15} and β_{0_45-60} values. The shaded regions indicate 95% bootstrap confidence intervals. c: Coupling stability for CA1 putative pyramidal cell pairs within each recording. Each plot shows, for one recording, all CA1 pyramidal cell pair GLM spiking correlations from the first 15 (β_{0_0-15}) and last 15 minutes (β_{0_45-60}) of the first hour of SWS.