Background
upper-limb motor learning, human behavior
Motor skill learning is crucial for optimizing human behavior and essential in a variety of daily life situations. The motor learning theory of Fitts and Posner [Moreover, the DLPFC is highly activated during the performance of unfamiliar or complex fine motor skill tasks with bimanual and unimanual non-dominant hands [Transcranial direct current electrical stimulation (tDCS) is a noninvasive brain stimulation technique that can modulate neuronal excitability in cortical and subcortical areas by inducing polarity-specific membrane potential changes. Depending on stimulus intensity and duration, anodal tDCS stimulation has generally been shown to increase neuronal excitability and to promote spontaneous neuronal firing and long-term potentiation, whereas cathodal stimulation has been shown to induce the opposite effect [Most previous studies evaluating tDCS effects in upper-limb motor learning in healthy individuals targeted the cortical motor areas and cerebellum [Commonly, these studies targeting the DLPFC demonstrated significantly improved performance in the active tDCS group compared to the sham group; meanwhile, the results of most previous studies targeting the other cortical motor areas and cerebellum were extremely inconsistent [Therefore, we hypothesized that anodal tDCS on the left DLPFC might enhance early manual dexterity skill acquisition of the non-dominant hand and would lead to greater learning gain in tasks with high cognitive demand.