Attention and fatigue scales between conditions. Level of attention and fatigue was presented by VAS, from 1: ‘no attention’ to 7: ‘highest level of attention’ and from 1: ‘no fatigue’ to 7: ‘highest level of fatigue’. Error bars indicate SEM. P values were from ANOVA and t-test (**P < 0.01, *P < 0.05). VR: virtual reality, tDCS: transcranial direct current stimulation, VAS: visual analog scale.