low-frequency rhythm 28, by measuring phase-phase coupling (PPC) 29. We tested for significant differences in PPC within the cluster of electrodes showing enhanced memory-related theta-gamma PAC. A two-tailed paired t-test on the mean across left temporal electrodes included in the PAC cluster produced no significant differences in PPC between blocks for either age group (ts41 < 0.754, ps > 0.455, dsz < 0.116) or stimulation condition (ts41 < 1.364, ps > 0.180, dsz < 0.210) (see Supplementary Fig. 1 for additional control analyses).
