The effect of transcranial direct current stimulation on the cortical activation by motor task in the human brain: An fMRI study

Objectives: We attempted to evaluate whether cortical activation resulting from hand movements is changed by transcranial direct current stimulation (tDCS) applied on the primary motor cortex for the hand in the human brain, using functional MRI (fMRI). Methods: Fourteen normal subjects were recruited; subjects were randomly assigned to either the tDCS group (n = 7) or the sham group (n = 7). fMRI was performed with hand grasp-release movements at 1 Hz before and after 20 min of intervention (the tDCS group: anodal tDCS, the sham group: sham stimulation). Results: The activation of the tDCS underlying primary sensorimotor cortex (SM1) was significantly increased in the tDCS group (p < 0.05). By contrast, the SM1 was significantly decreased in the sham group in terms of the voxel count and intensity (p < 0.05). No subjects complained of any adverse symptoms or signs. Conclusion: We demonstrated that anodal tDCS increased the cortical excitability of the underlying motor cortex in the human brain. It seems that tDCS is an effective modality to modulate brain function.