Anodal transcranial direct current stimulation (tDCS) over supplementary motor area (SMA) but not pre-SMA promotes short-term visuomotor learning

Abstract

Background: Non-invasive brain stimulation such as transcranial direct current stimulation (tDCS) has been shown to modulate cortical excitability and thereby influencing motor behaviour and learning.

Hypothesis: While there is increasing knowledge about the importance of the primary motor cortex (M1) in short- and long-term motor skill learning, little is known about the role of secondary motor areas such as the supplementary and pre-supplementary motor area (SMA/pre-SMA) especially in short-term motor performance. Since SMA but not pre-SMA is directly connected to M1, we hypothesize that anodal tDCS over SMA but not pre-SMA will facilitate visuomotor learning.

Methods: We applied anodal tDCS (tDCS(anodal)) over left SMA, pre-SMA or M1 (n=12 in each group) while subjects performed a visuomotor pinch force task (VPFT) with their right hand and compared VPFT performance relative to sham (tDCS(sham)).

Results: For the first time, we could show that apart from tDCS(anodal) over left M1 also SMA but not pre-SMA stimulation promotes short-term improvements in visuomotor learning relative to tDCS(sham).

Conclusions: Our findings provide novel evidence about the role of SMA in short-term visuomotor performance. This knowledge might be beneficial in developing hypothesis-driven clinical studies in neurorehabilitation.