Recently, non-invasive brain stimulation has become a powerful tool in both basic research and clinical application. Among several non-invasive brain stimulation techniques, transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) have received the most attention. About DC stimulation, the change of polarity could modulate the spontaneous neuronal activity and make effect on decision making, language, memory, sensory perception, and pain. In spite of that the concept of transcranial alternating current stimulation (tACS) is not novel, AC is relatively safe compared to DC, and researches have revealed that AC might potentially have the effect on the cortical excitability. However, there are still many areas about AC stimulation which remain unknown, such as mechanism, application, and potential influence on cortical excitability.

Inclusion Criteria:

• Healthy adults