Extended Data Fig. 2: Additional PAC analyses.

(a) PAC comodulogram averaged across all channels separately for each area. Strongest PAC was observed between theta and gamma in both areas of the MTL. Frontal areas did not show strong PAC, with weak PAC at <2 Hz in pre-SMA and vmPFC. We focused our analysis on frequencies above 2 Hz (1–3 Hz bandpass) to ensure that at least 2 full cycles fit within our analysis window of 2.5 s (length of maintenance period). (b) In addition to testing theta-gamma PAC across significant channels (see main text), we tested PAC between the load conditions across patients after averaging all significant PAC channels within each patient. The results were similar to the analysis across channels, with strongest PAC in MTL areas and only weak PAC in frontal channels (see percent of patients with significant PAC channels below each figure), suggesting that the results were not driven by channels from a single patient. Only in the hippocampus again, PAC was stronger for load 1 as compared to load 3 (n = 23 patients, p = 0.0049), observable in almost each single patient. No significant differences were found between the load conditions in other regions (amygdala: n = 25; pre-SMA: n = 4; dACC: n = 8; vmPFC: n = 13). z-scored PAC values were shifted into a positive range by an offset of 1 and log-transformed for illustrative purposes only. All statistics are based on non-transformed z-values. (c) Theta to low gamma (30–55 Hz) PAC analyses. We also found strongest theta-low gamma PAC in MTL regions as opposed to frontal regions (see percentages below each figure). But for the low gamma band, we did not observe significant differences between the load conditions in any of the regions (hippocampus: n = 148 channels; amygdala: n = 155; pre-SMA: n = 10; dACC: n = 22; vmPFC: n = 48). See Supplementary Table 2 for additional PAC analysis separated into slow and fast theta. In (b,c), we performed two-sided permutation-based t-test and centre values denote mean ± s.e.m.; ** p < 0.01; ns = not significant.