i think there is slight error in Fig. 6 description. "Electrodes placed on scalp areas over the blue shading would record positive potential." and " Electrodes placed on scalp areas over the blue shading would record negative potential.", i think you meant red shading in first sentence
i think there is slight error in Fig. 6 description. "Electrodes placed on scalp areas over the blue shading would record positive potential." and " Electrodes placed on scalp areas over the blue shading would record negative potential.", i think you meant red shading in first sentence