Correlations
hyperalgesia
To assess the clinical importance of the ICA findings, Pearson correlation was performed between the average z-score values (extracted at the peak MNI) of the significant clusters and placebo analgesia and nocebo hyperalgesia. The placebo analgesia effect was calculated as the difference between perceived intensity to identical moderate painful stimuli applied on areas of skin with lidocaine cream and those applied on areas of skin with neutral cream. The nocebo hyperalgesia effect was extracted as the difference between the perceived intensity to identical moderate painful stimuli applied on areas of skin with capsaicin cream and on areas of skin with neutral cream.Furthermore, we also extracted the average z-score values of the significant clusters using just the post tDCS on day 3 (the end of the treatment). Then, we performed another Pearson correlation between those clusters and placebo analgesia. Correlation analysis was performed using R software (Analyses that were conducted in this study are reported in 