Noninvasive brain stimulation was recently gradually be emphasized. The electrical current applied on scalp can effective modulate cortical excitability. Forms of Stimulation included transcranial direct current stimulation(tDCS) and transcranial alternating stimulation(tACS). tDCS had been proved the effect of cortical excitability modulation. The polarization effect of direct current stimulation can modulation specific brain area and enhance motor performance. tACS was still controversial about the effect on cortical excitability. Previous study show that the frequency dependent excitatory or inhibitory effect on cortex. The possible mechanism was to affect brain oscillation status by provided different frequency of stimulation. Transcutaneous nerve stimulation (TENS) was common used on management of chronic pain. Peripheral nerve stimulation can enhance pain or sensory evoked potential was noted. Effect of low frequency TENS on central nervous is unknown.
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