The purpose of this study is to investigate the cerebral activation during Classic Mirror Therapy (TMC) and especially during Virtual Mirror Therapy (TMV) in healthy subjects. It seems that the precuneus is involved in the effectiveness of mirror therapy. One goal of this study is to determine if there is a better activation of the precuneus during TMV than during TMC. Others goals are to compare cerebral activation during three different tasks (TMV, TMC and a simple motor task), to study the intra-subjects reproducibility of the measurement and the correlation between cerebral activation and feelings of the participants about the efficacity of the tasks.

Mirror therapy is a rehabilitation technique that has been shown to be effective in restoring upper limb motor skills in patients with stroke. However, it comes up against certain constraints of clinical use such as installation difficulties or the obligation of symmetrical bilateral work. These constraints can be limited by the use of so-called 2nd generation virtual mirror therapy technologies. It is therefore likely that these new technologies will improve the feasibility and effectiveness of mirror therapy in rehabilitation. While the brain mechanisms involved in mirror therapy are not yet fully understood, the involvement of the precuneus has been demonstrated by a booming imaging method: fNIRS (functional Near Infra Red Spectroscopy). This method allows (like fMRI) to study cerebral neurovascular coupling. It is based on the fact that an activated region of the brain increases its local blood flow. Oxygenated hemoglobin (HbO) and deoxygenated (HbR) absorb infrared light and it is then possible to identify the cortical regions of the brain involved in a given task. This technique therefore makes it possible to study brain activation under more ecological conditions than fMRI and is therefore particularly suitable for exploring rehabilitation techniques.

This research aims to study and compare in healthy subjects, using a fNIRS apparatus, the brain regions involved in the performance of a classic mirror therapy task and a virtual mirror therapy task with the IVS3 (Intensive Visual Simulation) apparatus (Dessintey Technology).

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 620 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 entire test will be repeated one week apart to assess the reproducibility of the measurements in healthy subjects.

The protocol has 3 conditions:

• A virtual TM task (TMV)
• A classic TM task (TMC)
• A control task (TC) Healthy subjects participating in the study will have two different acquisition times, each comprising 3 conditions.

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

If the subject can integrate the protocol, the two acquisition stages will then be scheduled one week apart.

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

The order of the 3 conditions will then be randomized to avoid potential biases linked to the sequence of conditions.

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

The acquisition under the 3 conditions is then carried out: TC1, TMC1, TMV1 with a rest time of 10 minutes between each condition.

The subject's feelings after the TMC and TMV conditions will be evaluated using the visual analogue scale (VAS). 0 corresponding to a zero feeling and 10 to a very important feeling. The subject will be explained that the feeling could correspond to tingling sensations, a desire to mobilize the hand which is behind the mirror, a "disturbing", "bizarre" sensation.

The helmet is only removed at the end of the 3 spots The subject returns a week later for the 2nd acquisition phase during which the same acquisitions as during the 1st meeting are carried out and then participation in the study is terminated.

There will therefore be 6 tests for each healthy subject.

Inclusion Criteria:

• Age:18 to 40
• Right handed
• No neurological disease

Exclusion Criteria:

• Known allergy to components of the fNIRS device: neoprene