The aim of this study is to investigate the effect of dual site-dual channel non-invasive brain stimulation for recovery of motor function in healthy subjects. Simultaneous dual site-dual channel stimulation was applied by using two sets of transcranial direct current stimulation devices. All subjects will go through four conditions of transcranial direct current stimulation with for 30 minutes. Four conditions are 1) Dual stimulation: i) anodal stimulation on right primary motor cortex and cathodal stimulation on left primary motor cortex, ii) anodal stimulation on right premotor cortex and cathodal stimulation on left supraorbital area. 2) M1 stimulation: anodal stimulation on right primary motor cortex and cathodal stimulation on left primary motor cortex; 3) PMC stimulation: anodal stimulation on right premotor cortex and cathodal stimulation on left supraorbital area. 4) sham stimulation

Inclusion Criteria:

• healthy subjects with age over 19 years old

Exclusion Criteria:

• history of disorders involving central nervous system
• patients with severe medial or psychiatric disease