Correlations
We performed Pearson correlation analyses between placebo analgesia and the average z values of the significant clusters found in the ICA analysis. We found a significant positive correlation between the right parietal operculum and DAN (the cluster showed a significant difference between the cathodal and sham comparisons) FC change (pre minus post tDCS) and the corresponding placebo analgesia (Furthermore, we performed the correlation between the DAN-operculum FC change and the placebo effect in the three tDCS groups separately. We found a significant correlation in the cathodal tDCS group (Further, we extracted the average z values of the significant clusters in the post-tDCS resting state after the last tDCS treatment and investigated the association between the FC and the placebo effects. We found a significant positive correlation between the right parietal operculum and DAN (same cluster as above derived from comparison between cathodal and sham groups (Finally, a trend was found between the left superior parietal lobule/precuneus and FPN (the significant cluster between the cathodal and sham groups) (No significant results were found in the correlations between the clusters and the nocebo effect.