The motor cortex drives the muscles during walking in human subjects

Key points • It is often assumed that automatic movements such as walking require little conscious attention and it has therefore been argued that these movements require little cortical control. • In humans, however, the gait function is often heavily impaired or completely lost following cortical lesions such as stroke. • In this study we investigated synchrony between cortical signals recorded with electroencephalography (EEG) and electromyographic signals (EMG activity) recorded from the tibialis anterior muscle (TA) during walking. • We found evidence of synchrony in the frequency domain (coherence) between the primary motor cortex and the TA muscle indicating a cortical involvement in human gait function. • This finding underpins the importance of restoration of the activity and connectivity between the motor cortex and the spinal cord in the recovery of gait function in patients with damage of the central nervous system. Indirect evidence that the motor cortex and the corticospinal tract contribute to the control of walking in human subjects has been provided in previous studies. In the present study we used coherence analysis of the coupling between EEG and EMG from active leg muscles during human walking to address if activity arising in the motor cortex contributes to the muscle activity during gait. Nine healthy human subjects walked on a treadmill at a speed of 3.5–4 km h−1. Seven of the subjects in addition walked at a speed of 1 km h−1. Significant coupling between EEG recordings over the leg motor area and EMG from the anterior tibial muscle was found in the frequency band 24–40 Hz prior to heel strike during the swing phase of walking. This signifies that rhythmic cortical activity in the 24–40 Hz frequency band is transmitted via the corticospinal tract to the active muscles during walking. These findings demonstrate that the motor cortex and corticospinal tract contribute directly to the muscle activity observed in steady‐state treadmill walking.