Fig. 2

Illustration of the stimulation electrode placements for a PMAs stimulation and b M1 stimulation during tDCS. SMA, supplementary motor area; PMC, premotor cortex. Supplementary motor area was defined as 1.8 cm anterior to the measured location of Cz [21]. Premotor cortex was defined as 2.5 cm anterior to the motor hot spot of the BB [22]. The hotspot of the BB is normally situated approximately 3 cm lateral and 2 cm in front of the Cz [23] and the hotspot of the TA is situated approximate 2 cm lateral and 1 cm in front of the Cz [24]