The enhanced cortical activation induced by transcranial direct current stimulation during hand movements

The aim of this study is to evaluate whether tDCS applied on the primary motor cortex (M1) in company with hand movements could enhance cortical activation, using functional MRI (fMRI). Twelve right-handed normal subjects were recruited. Real tDCS and sham tDCS with hand movements were applied during fMRI scanning. Subjects performed grasp-release hand movements at a metronome-guided frequency of 1 Hz, while direct current with 1.0 mA was delivered to the primary motor cortex. The averaged cortical map and the intensity index were compared between real tDCS with hand movements and sham tDCS with hand movements. Our result showed that cortical activation on the primary sensorimotor cortex was observed under both of two conditions; real tDCS with hand movements and sham tDCS with hand movements. Voxel count and peak intensity were 365.10 ± 227.23 and 5.66 ± 1.97, respectively, in the left primary sensorimotor cortex during real tDCS with right hand movements; in contrast, those were 182.20 ± 117.88 and 4.12 ± 0.88, respectively, during sham tDCS with right hand movements. Significant differences in voxel count and peak intensity were observed between real tDCS and sham tDCS (p < 0.05). We found that anodal tDCS application during motor task enhanced cortical activation on the underlying targeted motor cortex, compared with the same motor task without tDCS. Therefore, it seemed that tDCS induced more cortical activity and modulated brain function when concurrently applied with motor task.

Research highlights
► The aim of this study was to evaluate whether transcranial direct current stimulation (tDCS) applied on the primary motor cortex in company with hand movements could enhance cortical activation, using functional MRI.
► We found that simultaneous application of tDCS with motor task enhanced cortical activation on the underlying targeted cortex.
► It seemed that tDCS induced more cortical activity and modulated brain function when concurrently applied with motor task.