Modulation of spinal excitability during observation of bipedal locomotion.

This study investigated whether a mirror mechanism exists for bipedal locomotion. We employed the soleus (plantar flexor) Hoffman reflex to investigate corticospinal excitability at the spinal level during observation of bipedal locomotion. The differential amplitude modulation of the left soleus Hoffman reflex during observation of bipedal heel-stepping (plantar dorsiflexion) (324+/-53 microV), standing still (383+/-60 microV), and bipedal toe-stepping (plantar flexion) (419+/-53 microV) reached significance (P < 0.05). The observation of bipedal toe-stepping produced a greater increase in spinal excitability than the observation of bipedal heel-stepping. These findings support the suggestion that there is a mirror mechanism for bipedal locomotion and they demonstrate that spinal excitability for observation of bipedal locomotion mirrors that for execution of bipedal locomotion.