Regulation of Somatosensory Temporal Discrimination Threshold Through Motor Training: An EEG and Kinematics Study

Aims: Motor training enhances somatosensory temporal discrimination threshold (STDT), but the distinct neural mechanisms underlying actual execution versus motor imagery remain unclear. This study aimed to compare the effects of ball-rotation training (BRT; actual execution) and visual-guided imagery (VGI; motor imagery) on STDT, kinematic performance, and neurophysiological plasticity in healthy adults. Methods: Forty-eight right-handed participants were randomized into four groups: BRT (actual execution), VGI (motor imagery without movement), tactile control (simple gripping), and no-intervention control. Over seven days, participants underwent pre-/post-training assessments including kinematic analysis, STDT measurement, power spectral analysis and somatosensory-evoked potentials (SEPs). Results: BRT significantly enhanced motor performance (83% score increase vs. 21% in controls, p < 0.001) and movement speed (37% cycle time reduction vs. 12%–16% in others, p < 0.001), with partial transfer to the untrained hand. Both interventions reduced STDT but at distinct locations: BRT selectively improved index finger discrimination (64.02 ms → 43.75 ms, p = 0.007), while VGI enhanced palm sensitivity (73.43 ms → 61.13 ms, p = 0.003). Neurophysiologically, SEPs revealed increased spatial inhibition ratio (SIR) plasticity in both BRT and VGI (p < 0.001), correlating with STDT gains. EEG demonstrated BRT-induced gamma-band power increases in parietal regions and theta-band elevations in prefrontal cortex, whereas VGI modulated delta-band activity in ipsilateral parietal cortex. Conclusion: Actual execution (BRT) and motor imagery (VGI) enhance STDT through distinct neuroplastic mechanisms: BRT optimizes sensorimotor integration via parietal gamma/prefrontal theta oscillations, while VGI relies on ipsilateral parietal delta modulation. These findings underscore the role of cortical reorganization in motor learning and support tailored rehabilitation strategies for neurological disorders.