Modulation of cortico-muscular coupling associated with split-belt locomotor adaptation

Abstract

Humans can adjust their walking patterns according to the demands of their internal and external environments, referred to as locomotor adaptation. Although significant functional coupling (i.e. cortico-muscular coherence [CMC]) has been shown between cortical and lower-limb muscle activity during steady-state walking, little is known about CMC in locomotor adaptation. Therefore, we investigated the adaptation-dependent modulation of the CMC between the sensorimotor region and the tibialis anterior muscle using a split-belt locomotor adaptation paradigm that can impose an asymmetric perturbation. We hypothesized that the CMC would temporarily decrease after exposure to the asymmetric perturbation and removal of the perturbation because of a mismatch between the predicted and actual sensory feedback. We also hypothesized that the CMC would increase as adaptation and de-adaptation to perturbation progressed because the motor system could become able to predict sensory feedback. Our findings revealed that the CMC temporarily decreased after exposure to and removal of the perturbation. Moreover, the CMC increased with adaptation and de-adaptation to perturbation. Although these results depend on the leg, frequency bands, and gait phases, they partially support our hypothesis. These findings suggest that flexible updating of cortico-muscular coupling in the motor system is a key mechanism underlying locomotor adaptation in humans. The results from our study on healthy young individuals contribute to the understanding of neuromuscular control of gait and provide valuable insight for optimising gait rehabilitation. Key pointsO_LILocomotor adaptation plays a crucial role in our daily activities and gait rehabilitation. C_LIO_LIAlthough knowledge regarding the brain and muscle activities associated with locomotor adaptation has been accumulated, little is known about the functional coupling of the brain and muscle activities. C_LIO_LIUsing high-density EEG and lower limb EMG, we demonstrated the modulation of cortico-muscular coherence between the sensorimotor region and the tibialis anterior muscle with adaptation and de-adaptation during a split-belt treadmill walking paradigm. C_LIO_LIOur findings suggest that flexible updating of cortico-muscular coupling in the motor system underlies locomotor adaptation in humans. C_LIO_LIUnderstanding the human brains control of muscles during split-belt locomotor adaptation will deepen our knowledge of neuromuscular control of gait and provide valuable insights for gait rehabilitation. C_LI