Fig. 3

Electrical fields of cathodal transcranial direct current stimulation (tDCS) in each group. A target electrode (cathodal) placed over the left motor cortex (C3) and a reference electrode (anodal) placed over the right supraorbital area (Fp2). Finite element models of tDCS application. Slice positions (ROAST’s MNI152 head) are taken at MNI coordinates of − 53, − 16, and 47 for sagittal, coronal, and axial slices, respectively. In the sagittal and coronal views, the gray circle represents the position of the electrode, and the black arrows represent electrical current flow in the brain. The red color represents the higher electric field, and the blue color represents the lower electric field in the brain. Compared to 1.5 and 2 mA cathodal tDCS, in 1 mA (coronal view), the electric field is higher