Cortical control of normal gait and precision stepping: an fNIRS study

Recently, real time imaging of the cortical control of gait became possible with functional near-infrared spectroscopy (fNIRS). So far, little is known about the activations of various cortical areas in more complex forms of gait, such as precision stepping. From previous work on animals and humans one would expect precision stepping to elicit extra activity in the sensorimotor cortices (S1/M1), supplementary motor area (SMA), as well as in prefrontal cortices (PFC). In the current study, hemodynamic changes in the PFC, SMA, M1, and S1 were measured with fNIRS. In contrast to previous fNIRS gait studies, the technique was optimized by the use of reference channels (to correct for superficial hemodynamic interference). Eleven subjects randomly performed ten trials of treadmill walking at 3 km/h (normal walking) and ten trials of 3 km/h treadmill walking on predefined spots for the left and right foot presented on the treadmill (precision stepping). The walking trials of approximately 35 seconds were alternated with rest periods of 25-35 seconds consisting of quiet standing. The PFC revealed profound activation just prior to the onset of both walking tasks. There was also extra activation of the PFC during the first half of the task period for precision stepping. The SMA showed mainly increased activation prior to the start of both tasks. In contrast, the sensorimotor cortex did not show a change in activation during either task as compared to a condition of standing. The SMA, M1, and S1 revealed no significant differences between normal walking and precision stepping. It was concluded that fNIRS is suited to record the planning and initiation of gait. The lack of M1/S1 activation during gait suggests that even in the current precision stepping task the control of ongoing gait depended mostly on subcortical automatisms, while motor cortex contributions did not differ between standing and walking.