From Movement Preparation to Gait Execution in ALS

This research program will focus on gait initiation and postural control in Amyotrophic Lateral Sclerosis (ALS) patients, by comparing patients with vs without postural instability (but also in comparison to controls), by using a multidisciplinary approach which combines neurophysiological and neuroimaging analyses. After clinical evaluation, two groups of ALS patients, defined upon the feature of postural instability, and one group of healthy subjects (n=25 for each group of patients and 20 for healthy subjects) will be included in the study. The neurophysiological evaluation will be performed through a gait initiation assessment, which will alow us to collect biomechanical and electromyographical data, such as the braking index. The neuroradiological evaluation will include first an fMRI analysis, a study of specific circuits in networks will be performed which will provide the first description of neural network dynamics associated with the preparation and execution of movement in ALS patients. The investigators major research hypothesis is: * By comparing patients with vs without postural instability, but also in comparison to controls, the investigators main research neurophysiological hypothesis is that patients with postural instability will display an impaired braking. * This impaired braking could be partly explained by a dysfunction and/or lesion of the basal ganglia and brain stem structures, corresponding to the investigators main neuroradiological hypothesis.