Statistical analyses
The normal distribution of each data set was evaluated by the Shapiro–Wilk normality test. Values are presented as means and standard deviation (SD) or median and interquartile range (IQR) as stated. The Friedman test was used to compare tDCS-induced sensations, end-of-study guess rate accuracy, and active stimulation guess rate, followed by Wilcoxon signed-rank tests with a Bonferroni correction for pair-wise comparisons (0.05/6 = Bonferroni corrected One-way repeated measures ANOVA was performed to analyze the mean value of TTE, HR, SpO