Effects of Transcranial Direct Current Stimulation over the Left Sensorimotor Cortex on Bimanual Force Control: A...

Transcranial direct current stimulation (tDCS) over motor-premotor regions may modulate motor performance, though underlying mechanisms remain unclear. Twenty-four athletes (9 females, 15 males) were randomly assigned to receive anodal tDCS (2 mA, 20 min) over the left sensorimotor cortex (n = 12) or sham stimulation (n = 12). Participants performed a bimanual isometric force-matching task at 30% maximal voluntary contraction, with visual feedback initially provided and then removed. Force undershoot, root mean square error (RMSE), spectral power (1-3 Hz), and inter-hand coherence were analyzed. A computational model was developed to test whether enhanced proprioceptive feedback processing could account for observed effects. Following tDCS, force undershoot decreased significantly (p = 0.002, d = -1.15) and RMSE improved (p = 0.010, d = -0.91). Spectral power in the 1-3 Hz band increased (p = 0.012, d = 0.87), suggesting enhanced corrective oscillations. These within-group changes were absent in the sham group (all p > 0.20), although Group × Epoch interactions did not reach significance (all p > 0.05), likely due to limited statistical power. Inter-hand coherence remained unchanged. The computational model demonstrated that enhanced proprioceptive feedback gain qualitatively reproduces the observed behavioral pattern. Anodal tDCS over the left sensorimotor/premotor region may enhance bimanual force control under conditions requiring proprioceptive feedback. Replication with larger samples is needed to confirm between-group specificity.