The goal of this clinical study is to investigate the potential synergy between non-invasive brain and spinal cord stimulation administered during a cognitive-motor task, in terms of their immediate effects on sensorimotor and cognitive functions after neurological injuries affecting the upper limb (cervical spinal cord injury and stroke). Secondary objectives are to evaluate the relevance of anatomical MRI, functional MRI, and neurophysiological measurements for optimizing and predicting the effects of these different interventions.

Over the past decade, innovative electrical stimulation strategies have emerged to improve the effectiveness of conventional rehabilitation approaches following spinal cord injury or stroke. Transcranial direct current stimulation (tDCS) and transcutaneous spinal cord stimulation (tSCS) are two non-invasive stimulation techniques targeting respectively the brain and spinal cord. These techniques have demonstrated immediate and lasting positive effects on the recovery of lost neurological functions following damage to the brain (in the case of stroke) or the spinal cord (in the case of spinal cord injury). Functional improvements leading to a better quality of life have been demonstrated in response to tSCS or tDCS sessions combined with motor training. Recent studies suggest a potential synergistic effect of these two types of intervention, which we propose to characterize in control participants, participants with cervical spinal cord injury, and post-stroke participants.

OBJECTIVES: In this project, we seek to study the potential synergistic effects of an intervention combining non-invasive stimulation of the brain and spinal cord, administered during the performance of a cognitive-motor task, compared to a control intervention and each intervention administered separately, on the recovery of motor and cognitive-motor functions after neurological injury. Secondary objectives are to evaluate the relevance of anatomical MRI data and neurophysiological measurements for optimizing and predicting the effects of these different interventions.

METHODOLOGY/RESEARCH DESIGN: Single-center, prospective, comparative, randomized, crossover, and single-blind clinical study comparing four neuromodulation interventions: S1: tDCS, S2: tSCS, S3: tDCS-tSCS, S4: sham, administered during a cognitive-motor training task of the affected upper limb using the Armeo technology. Three groups of participants will be included: one control group, one group with cervical spinal cord injury, and one post-stroke group. The two groups with either spinal cord injury or stroke will participate in a total of nine visits: the inclusion visit, four testing visits, and four intervention visits. The control group will participate only in the inclusion and testing visits. Outcome measures will include neurophysiological and clinical performance measures.

Inclusion Criteria:

CONTROL GROUP:

• Over 18 years of age
• Participant who has signed an informed consent form
• Participant who is affiliated with and covered by the social security system

POST-STROKE GROUP:

• Over 18 years of age
• Who sustained a stroke more than 3 weeks ago
• Considered medically stable by the medical investigator
• Who has signed an informed consent form
• Affiliated with and covered by the social security system

SCI GROUP:

• Over 18 years of age
• Considered to have a complete or incomplete spinal cord injury (i.e., with a score on the Spinal Injury Association (ASIA) Impairment Scale (AIS) score from A to D)
• Considered medically stable by the investigating physician
• Presenting with quadriplegia due to cervical injury
• Who has signed an informed consent form
• Affiliated with and covered by the social security system.

Exclusion Criteria:

• Suffering from a chronic condition
• Skin problems or open wounds
• History of epilepsy or seizures
• Presence of a contraindication to the use of magnetic/electrical stimulation or MRI, including: cardiac pacemaker; implanted hearing aid; intraocular foreign body, shrapnel, or bullets; metal worker; pacemaker or neurostimulator; claustrophobia
• Presence of implanted medical devices (cardiac valve, endovascular devices, ventricular shunt valve, surgical clips, metallic sutures, staples, stent, osteosynthesis or arthrodesis hardware) not classified as "MR Conditional" according to ASTM F2503.
• Individuals who are legally incompetent, under judicial protection, guardianship, or trusteeship
• Pregnant and/or breastfeeding women
• Individuals who refuse to be informed of any abnormalities that may be detected by MRI.

Based on request and on the data type requested and ethically approved (only non-personally Identifiable Information).