Transcranial Direct Current Stimulation for Gait Recovery Following Stroke

Background: Stroke is a leading cause of adult disability. The ability to walk is considered as the most important physical activity in daily life and strongly associated with quality of life in patients with stroke sequela. Conventional transcranial Direct Current Stimulation (tDCS) can induce mixed effects to improve gait impairment after stroke. The problem of limited focal specificity of tDCS may lead to an ineffective stimulation and in turn may be reduced the potential application of tDCS in clinical routine. High-definition transcranial Direct Current Stimulation (HD-tDCS) allows inducing, in a non-invasive way, a transient excitatory neuromodulation of a given cerebral region and to obtain a very focused cortical effect. However, the clinical and neurophysiological effects of HD-tDCS remain largely unknown for enhancing gait recovery in patients with stroke. The investigators hypothesize that anodal HD-tDCS will enhance neural interactions between motor networks and, thereby, improve motor processing and gait relearning. The investigators propose to carry out a study on chronic stroke patients involving anodal HD-tDCS of the affected primary motor cortex combined with a physical therapy. This study has three main objectives: * To compare the effects of two techniques of tDCS (anodal tDCS, anodal HD-tDCS) on clinical recovery in patients with chronic stroke. * To assess the effects of these brain stimulation techniques on brain reorganization with electroencephalography (EEG). * To assess the effects of these brain stimulation techniques on spatiotemporal gait parameters during walking with wearable motion sensors. Methods: 36 patients with ischemic or hemorrhagic stroke will be randomly assigned to one of 3 groups: anodal tDCS, anodal HD-tDCS, or sham stimulation. Each group will receive the corresponding stimulation therapy 3 times per week for 2 weeks, simultaneously with physical therapy. Before (T0) and immediately after the treatment period (T1) and again one month later (T2), standardized assessments of sensorimotor function areas are obtained together with spatio-temporal analysis. Brain reorganization is assessed with EEG before and immediately after the treatment period. These recordings will be used to compare and investigate the clinical and physiological effects of each treatment modality.