Characterization of cortical activation patterns during movements in healthy adults may help our understanding of how the injured brain works. Upper limb motor tasks are commonly used to assess impaired motor function and to predict recovery in individuals with neurological disorders such as stroke. This study aimed to explore cortical activation patterns associated with movements of the hand and shoulder using functional near-infrared spectroscopy (fNIRS). The investigators hypothesized that the activation pattern observed with fNIRS would differ for shoulder and hand movements. More specifically, the investigators hypothesized that the cerebral activation during hand movements would mainly involve the contralateral hemisphere, particularly the lateral part of primary motor cortex; whereas activation during shoulder movements would be more medial and more extensive than that of the hand.

Stroke is a leading cause of chronic disability worldwide in adults. Upper extremity (hand and arm) impairments are especially prevalent after stroke and cause lasting disabilities. Functional reorganization of the motor cortex may occur in both the ipsilesional and contralesional hemispheres. Thus, knowledge of brain activation patterns during execution of a movement is important both for neuroscience and neurorehabilitation.

The use of brain imaging techniques for post-stroke follow-up is valuable for understanding the mechanisms of cerebral recovery. Functional Near-Infrared Spectroscopy (fNIRS) is a non-invasive technique that assesses neural activation through the measurement of cortical oxygenated and deoxygenated hemoglobin concentrations during motor tasks in a natural.

As remapping of the sensorimotor cortex after stroke with hand impairment can involve the territory of the elbow or shoulder, the investigators aimed to determine if the cortical activation of these regions (hand and shoulder) could be distinguished by fNIRS recordings in healthy subjects. The investigators hypothesized that the activation pattern observed with fNIRS would differ for shoulder and hand movements. More specifically, the investigators hypothesized that the cerebral activation during hand movements would mainly involve the contralateral hemisphere, particularly the lateral part of primary motor cortex; whereas activation during shoulder movements would be more medial and more extensive than that of the hand, involving the contralateral premotor region and supplementary motor cortex. If these three cortical regions could be distinguished by fNIRS, this technique could be used to measure spontaneous motor recovery and rehabilitation-induced recovery after stroke.

The investigations will be carried out by the principal investigator or by specialized technicians from the neurology functional exploration department.

Each acquisition has a duration of 920 seconds, it begins with a rest period of 120 seconds, which corresponds to the baseline.

For each condition the movements are performed at a frequency of 0.5 Hz which seems to be the optimal frequency for observing cortical activation using a metronome. Each movement is therefore performed 10 times per block.

The order of placing the various conditions will be balanced. Between periods of movement, the subject is in a resting position for 30 seconds.

The "movement" and "rest" instructions are given at the start of each phase.

The protocol has 2 conditions:

• Shoulder task
• Hand task

After recruiting the participants, the study investigator will check the inclusion and non-inclusion criteria.

On the day of the first acquisition, the subject will present to the neurology department at the time of his appointment.

Then the fNIRS acquisition headset (Brite 24) will be installed by a specialized technician and the procurement instructions will be given.

The acquisition is then carried out. The helmet is only removed at the end of the acquisition

Inclusion Criteria:

• Age:18 to 40
• Right handed
• No neurological, rhumatological or cardiac disease
• Having social security coverage
• Having expressed his non-objection

Exclusion Criteria:

• Person under tutorship or curatorship
• Known allergy to components of the fNIRS device: neoprene
• Person with known vascular problems

right handed healthy subjects aged between 18 and 40