Transcranial direct current stimulation (tDCS) is one of the noteworthy noninvasive brain stimulation techniques, but the mechanism of its action remains unclear. With the aim of clarifying the mechanism, we developed a rat model and measured its effectiveness using fMRI. Carbon fiber electrodes were placed on the top of the head over the frontal cortex as the anode and on the neck as the cathode. The stimulus was 400- or 40-mu A current applied for 10 min after a baseline recording under an anesthetized condition. The 400-mu A stimulation significantly increased signal intensities in the frontal cortex and nucleus accumbens. This suggests anodal tDCS over the frontal cortex induces neuronal activation in the frontal cortex and in its connected brain region. (C) 2011 Elsevier Ireland Ltd. All rights reserved.