Optimizing Motor Skills with HD-tDCS: Insights from a Pilot Study on Chopstick Proficiency

This study extends our previous research on neurological adaptations associated with learning to use chopsticks, in which we observed increased functional activity and connectivity changes in the anterior supramarginal gyrus (aSMG), a brain region previously implicated in novel tool use. In the present study, we investigated the effects of high-definition transcranial direct current stimulation (HD-tDCS) on motor learning by applying anodal stimulation to the aSMG in a double-blind, sham-controlled design with 24 participants (12 active, 12 sham). Participants in the active condition received [~]3 mA of HD-tDCS focused over the aSMG while watching a 20-minute video of the task - picking up a marble with chopsticks and dropping it into a cylindrical container. In comparison, participants in the sham condition watched the same video while receiving sham stimulation consisting of a 30-s ramp-up and ramp-down at the start and end of the 20-minute video. Immediately after the video task, all participants completed 15 one-minute trials in which they performed the task while electroencephalography (EEG) was recorded. Performance was assessed by the average number of successful marble drops per minute (MDPM) across trials. Additionally, video-based motion was analyzed using DeepLabCut to compare key kinematic metrics, providing insights into subtle variations in movement patterns during the marble task. Results showed a significant increase in MDPM in the active stimulation group compared to the sham group (17. 3 vs. 14. 1 MDPM; p < .05). Kinematic data showed increased movement jerk in the active stimulation group compared to sham (21719 vs 16926; p < .05), and EEG revealed differences in task-related gamma-band power over Cz (.0227 vs -.0758; p < .05). These findings suggest that HD-tDCS enhances the rate of motor learning in novel tool use and underscore the potential of aSMG-targeted stimulation in facilitating complex motor tasks. Further studies are warranted to explore the broader applicability of HD-tDCS in skill acquisition and rehabilitation. New and NoteworthyThe presented study shows the role that the left anterior supramarginal gyrus plays in experience-independent tool learning. Anodal HD-tDCS applied during action observation increased performance in a subsequent chopstick skill acquisition task. This increase in performance was accompanied by enhanced task-related gamma-band activity and altered movement kinematics. By linking neuromodulation of the parietal tool-use hub to behavioral, kinematics, and electrophysiological changes, these findings significantly advance our understanding of how higher-order sensorimotor networks support tool-use learning.