Fig. 1.

a Experimental design. The effect of tDCS on the leg motor cortex was examined in the PF and RT tasks. In the PF task the maximal pinch strength of the left leg was measured. In the RT task the subjects responded to a visual stimulus by using the left leg as quickly as possible. All subjects participated in anodal-tDCS, cathodal-tDCS and sham-stimulation experimental sessions, and each session consisted of four blocks of the PF task and five blocks of the RT task. After subjects performed a block of the PF and RT tasks, 2 mA tDCS over the leg motor cortex was applied for 10 min. The spatial focality of tDCS effect was evaluated by also measuring the PF and RT when the tasks were performed with the left hand. b Leg pinch force device. Maximal PF of the left great toe and the digitus secundus was assessed using a toe-gap force measurement device. Subjects were seated in an armchair and asked to squeeze the gauge as hard as possible for 1–3 s