Effect of Rhythmic Auditory Stimulation (RAS) During Gait on Cortical Activation: A Functional Near-infrared Red Spectroscopy Neuroimaging Study (fNIRS)

Gait and balance impairments caused by neurological disorders affect many people around the world and impact on independent living and quality of life. Gait rehabilitation is therefore highly important for individuals with neurological diseases. In recent years, rehabilitation strategies were carried out considering new technological devices and paradigms have been developed to increase the effectiveness of rehabilitation. Brain and clinical research have provided a new understanding of the capabilities of music to engage and shape motor functions to support brain recovery processes. Humans possess an ability to perceive and synchronize movements to the beating music. In context of motor rehabilitation, musical rhythm entrains movement in patients with neurological impairment, opening new frontiers for using rhythm and music to prime the motor system and favour improvement of deficiency consequences. Rhythmic auditory stimulation (RAS) is a gait rehabilitation method in which patients synchronize foot steps to a metronome or musical beats. Typically, rhythmic cues are matched to the individual's preferred cadence and, once the movement is entrained to the external cues, the rhythm is gradually increased by 5-10% over baseline. However, little is known about the neural correlates of gait during RAS.

fNIRS (functional Near Infra Red Spectroscopy) is a functional method that allows to study the cerebral cortex changes during different tasks (like fMRI). This technique therefore makes it possible to study brain activation under more ecological conditions than fMRI and are therefore particularly suitable for exploring rehabilitation techniques.

This research aims to study and compare in healthy subjects, using, the brain regions involved in 4 conditions of gait without and with rhythmic auditory stimulations.

The protocol has 4 conditions :

• Gait at preferred cadence without auditory stimulation (Gait1)
• Gait with low tempo rhythmic auditory stimulation by music (RAS-Slow). The beat rate of the music was 68.5 per minute for all participants.
• Gait with fast tempo synchronous rhythmic auditory stimulation by music (RAS-Fast). The beat rate of the music was set to 10% above each patient's preferred gait cadence . The preferred cadence was considered as the mean of the 6 trials during Gait 1.
• Gait without auditory stimulation (Gait2) The investigators choosed a fixed order rather a randomized one, because the use of auditory stimulation may interferes with subsequent tasks. The comfortable gait was proposed as first and last conditions to check this aftereffect.