Article Figures & Data
Figures
- Figure 1.
Experimental paradigm (A), ROIs (B), and dynamic analysis pipeline (C). A, Experimental design. Participants underwent simultaneous RS EEG–fMRI recordings before and after tACS/sham stimulation. Each recording session lasts 10 min. B, ROIs. Abbreviations: (l/r) AI, (left/right) anterior insula; dACC, dorsal anterior cingulate cortex; (l/r) dlPFC, (left/right) dorsolateral prefrontal cortex; (d/v) PCC, (dorsal/ventral) posterior cingulate cortex; (l/r) PPC, (left/right) posterior parietal cortex; mPFC, medial prefrontal cortex; (l/r) AG, (left/right) angular gyrus. C, Analysis pipeline illustrating the methods used (see text for more details).
- Figure 2.
α-tACS strengthened dynamic coupling between DMN connectivity and alpha power. A, Mean changes (Post–Pre) in the dynamic coupling matrix for the active (top right) and sham control (bottom left) groups across subjects. B, C, Boxplots illustrate increased coupling (from Pre to Post) between fluctuation of alpha power and PCC–rAG (B) and PCC–lAG (C) connectivity in the active (vs sham) group. The red- and blue-shaded areas correspond to the mean ± 1.96 × SEM and the mean ± 1.96 × SD, respectively. For the double contrasts, * = p < 0.05 FDR corrected; p < 0.1 FDR corrected. For the follow-up simple contrasts, p < 0.1; *p < 0.05. The dynamic coupling between alpha power and connectivity of DMN with the CEN and SN, and baseline alpha–DMN coupling are shown in Extended Data Figures 2-1 and 2-2, respectively.
- Figure 3.
Data from a representative participant. A, B, For each pair of ROIs (here, vPPC and right AG), average BOLD signals were extracted using a sliding Gaussian window of 60 TRs (∼2 min; A). The two BOLD timeseries for each sliding window were then correlated, resulting in a r coefficient (i.e., FC strength). Congregating the r values for all windows (sliding in increments of 1 TR) across the Pre (left) and Post (right) recordings, we obtained the respective FC timeseries (B). C, D, Similarly, we obtained an alpha power timeseries for the Pre (left) and Post (right) sessions (C). Specifically, we extracted alpha power from each sliding window and congregated alpha power from all windows for Pre and Post sessions, respectively (D). Finally, we correlated the timeseries of FC and alpha power for each session (B, C) and obtained an index of dynamic alpha–FC coupling. In this participant, the coupling increased from −0.62 Pre (left) to 0.82 Post (right).
- Figure 4.
α-tACS modulation of dynamic coupling across brain networks and frequency bands. A, No effect of α-tACS on the dynamic coupling between DMN connectivity and beta or theta power. Mean differential (Post–Pre) dynamic coupling matrices were comparable between active (top right) and sham (bottom left) groups for beta (left) and theta (right) band power. B, No effect of α-tACS on the dynamic coupling between alpha power and CEN/SN connectivity. Mean differential (Post–Pre) dynamic coupling matrix of connectivity within and between CEN and SN was comparable between active (top right) and sham (bottom left) groups. No effects survived the significance threshold (p < 0.05 FDR corrected). C, Effects of the lag size. P and corrected p values for the effect of tACS on the dynamic coupling of alpha (blue lines) with vPCC–rAG (left) and vPCC–lAG (right) connectivity were consistently significant (gray shaded area) over lags of zero to five TRs. In contrast, beta (red lines) and theta (black lines) showed stable, nonsignificant patterns over the same lags.
- Figure 5.
α-tACS strengthened dynamic coupling between adjusted DMN connectivity and alpha power. A, Changes (Post–Pre) in the dynamic coupling matrix for the active (top right) and sham control (bottom left) groups. B–D, Boxplots illustrate increased coupling (from Pre to Post) between fluctuation of alpha power with mPFC–lAG connectivity (B), PCC–rAG connectivity (C) and PCC–lAG connectivity (D) in the active (vs Sham) group. The red- and blue-shaded areas correspond to the mean ± 1.96 × SEM and the mean ± 1.96 × SD, respectively. For the double contrasts, p < 0.1 FDR corrected; *p < 0.05 FDR corrected. **p < 0.01 FDR corrected. For the follow-up simple contrasts, ·p < 0.1 uncorrected; *p < 0.05 uncorrected; **p < 0.01 uncorrected.
Extended Data
Figure 2-1
No effect of α-tACS on the dynamic coupling between alpha power and connectivity of DMN with the CEN and SN: Differential (Post – Pre) dynamic coupling matrices were comparable between Active and Sham groups. No significant effects of tACS were observed. Download Figure 2-1, TIF file.
Figure 2-2
Baseline alpha-DMN Coupling: Baseline data pooled between the two groups showed no reliable coupling between alpha and DMN connectivity timeseries. The lower left and upper right portions of the matrix reflect the r and t values, respectively. Download Figure 2-2, TIF file.
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