Evaluation of the Impact of Laterality on Brain Activation During a Virtual Mirror Therapy Task in Healthy Subjects

Stroke frequently leads to upper limb deficit. The recovery of motor skills depends on many factors including laterality. The literature shows that cerebral activation during motor tasks differs depending on whether one is right-handed or left-handed and whether one uses the dominant hand or not. These differences probably lead to different recovery mechanisms depending on the side of the lesion and the laterality. An imaging technique is particularly suitable for exploring these different mechanisms: 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 brain region increases its local blood flow. Oxygenated (HbO) and deoxygenated (HbR) hemoglobin absorb infrared light and it is then possible to identify the cerebral cortical regions involved in a given task. This technique therefore makes it possible to study cerebral activation under more ecological conditions than fMRI and is thus particularly suitable for exploring rehabilitation techniques.

This research aims to study and compare in healthy subjects, using an fNIRS apparatus, the brain regions involved in a virtual mirror therapy task according to the laterality of the task.

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

The acquisition has a duration of 15 minutes, it begins with a rest period of 120 seconds, which corresponds to the baseline. two different tasks are performed during the acquisition for each subject:

• observation of visual feedback of the right hand (RVF)
• observation of visual feedback of the left hand (LVF)

The design is a block design, each task, which has a duration of 20 seconds, is carried out 10 times per acquisition. There is therefore a total of 20 tasks whose order will be randomized.

Before each acquisition, the movements of the right and left hands (finger flexion and extension) are recorded by a camera integrated in the virtual mirror therapy tool. Movements are performed at a frequency of 0.5 Hz which appears to be the optimal frequency for observing cortical activation using a metronome.

Between periods of movement, the subject is in a rest position for a period from 15 to 25 seconds.

The instructions given to each subject are to observe the visual feedback on the screen and not to perform any movement during the acquisition.

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

If the subject can integrate the protocol, the acquisition will then be planned.

On the day of the acquisition, the fNIRS acquisition helmet (Brite MKII) will be installed by a specialist technician and instructions will be given. The recording is then made.

Inclusion criteria

• Age:18 to 60
• Right handed
• No neurological disease

Exclusion criteria

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