Fig. 1

Schema of cross-frequency graphs. For simplicity, we display only three brain sources (X, Y, Z) and three frequency bands (Band 1, Band 2, Band 3), although in the study 1210 brain sources and five frequency bands were used. (A): we calculated the MEG signal of each source, which was then divided by frequency; the signals were then orthogonalized, and the envelopes calculated. The absolute value of the Pearson correlation between envelopes was used as weight for the graph edges. (B): the upper panels show two examples of the correlation calculation: one for inter-band connections and one for intra-band connections; the lower panels display the resulting graph (left) and outline how each node has intra-band connections (solid-colored lines) and inter-band connections (dotted-black lines), accounting for the interplays between bands (right). Although they are represented differently in the figure, both types of edges were treated equally in the centrality metrics’ calculations