Experimental procedure
’ adverse effects, pain
The experimental procedure consisted of three phases: pre-assessment, assessment, and post-assessment (Fig. Schematic representation of the experimental procedure and design. In the assessment phase, all participants performed the two PPT subtests (the left-handed peg and the assembly task, see the A 10-min rest period separated each assessment phase. Participants were informed that they would receive “two different intensities of forehead stimulation” and were blinded to the stimulation mode. A schematic illustration of active and sham stimulation is shown in Fig. After stimulation, during the post-assessment phase, the success of blinding was measured by asking participants to guess whether they had received active or sham tDCS to justify its effectiveness on early-phase dexterity acquisition. Additionally, subjective discomfort (pain) was measured using a sensation questionnaire to identify participants’ adverse effects, safety, and tolerability [