Study timeline (Fig. 
SESSION
In total, each subject attended nine sessions. Session one to eight happened within one months’ time (pre-training in week 1, six training sessions in week 2 and 3, post-training in week 4). The last session (follow-up) was conducted three months later. During each session subjects carried out the PASAT, however tDCS was applied only during training sessions. Training sessions alternated with one training-free day.