Transcutaneous auricular vagus nerve stimulation reduces error amplitude during force field learning in healthy adults

Transcutaneous auricular vagus nerve stimulation (taVNS) has gained increasing attention as an expected new clinical application for motor disease due to its synergistic effect with post-stroke rehabilitation. On the other hand, there are still few reports regarding the effects of taVNS on motor learning in healthy subjects. In the present study, we investigated how taVNS affects a reaching movement task under a force field condition (i.e., force field learning). A total of 32 healthy, right-handed subjects were divided into a taVNS and a sham group. Subjects were asked to make reaching movements with their right arm while holding the handle of the manipulandum against a velocity-dependent curl force field. taVNS was applied for 3 s at the start of the reaching movement. The results demonstrated that taVNS reduced the maximum rightward displacement (i.e., error amplitude) during force field learning, and the final values were significantly smaller in taVNS groups than in sham groups. These results suggest that taVNS matched with task initiation has an online effect on force field learning.