Fig. 3

Overview of transcranial direct current stimulation montages in the included randomized controlled trials. Blue squares/rectangles indicate cathodes, while red squares/rectangles indicate anodes. Electrodes’ shape and dimension reflect the differences in RCTs stimulation setups. Solid lines connect the electrodes pairs that have been tested in different stimulation conditions in each RCT. The positions of anodes and cathodes are identified according to the international 10/20 electroencephalographic system. *This study assessed both cathodal and anodal stimulation. **10/10 electroencephalographic system