Study of activation in motor cortex during mental imagery of walking using fNIRS

A walking rehabilitation system is proposed which includes both muscle strength enhancement by walking rehabilitation machines and neurological rehabilitation by imaginary walking. In a previous study, we have demonstrated that the concentration of oxygenated hemoglobin (oxy-Hb) in motor area during imaginary walking was higher than that during real walking by means of fNIRS (functional Near-InfraRed Spectroscopy). In order to develop an effective way to activate the motor area in mental imagery, we compared the activation in motor area during real walking (RW), virtual walking (VW), and walking observation (WO). In the VW, subjects were shown moving scenes of a virtual visual environment in which subjects easily imagined as if they were actually walking from the first-person perspective. In the WO, subjects were instructed to imagine that they were walking with the same pace to a person in the video being shown to the subjects (third-person perspective). Four subjects participated in the experiment. As a result, the oxy-Hb in motor area during both VW and WO were higher than that during RW on the average. This was because that it was not necessary to pay attention to the movements of the legs and feet during normal walking, while movement planning was required when the subjects imagined their walking in the same way to another person. There was no significant difference between the oxy-Hb during VW and that during WO. The importance of stimulus diversity in mental imagery of walking was suggested.