Boxplots and single trials scatter plots showing the effect of offline stimulation condition on transition latency (A) in continuation and (B) in switching transitions. Switching transitions in the offline 20 Hz condition were comparably faster than those in the offline 10 Hz condition. Computed variables for boxplots: lower/upper whiskers represents smallest/largest observation greater than or equal to lower hinge ± 1.5 * inter-quartile range (IQR), lower/upper hinge reflects 25%/75% quantile, lower edge of notch = median − 1.58 * IQR/sqrt(n), middle of notch reflects group median, red asterisks represent group mean. (C) Diverging effect of time progression in the two different offline stimulation conditions on cumulative error rate. While a decrease of error rate was found for the offline 10 Hz condition, an increase in error rate was found in the offline 20 Hz condition over time (p < 0.01) in continuation trials. Regression line with 95%CI presented for each group. Offline 10 Hz tACS is depicted in grey, offline 20 Hz tACS depicted in black in non-stimulated trials pooled over coordination pattern (IP, AP).