The goal of this clinical trial is to study the effect of Transcutaneous Auricular Vagus Nerve Stimulation (taVNS) on resting-state brain functional connectivity. The study will assess this effect using functional Near-Infrared Spectroscopy (fNIRS) in both chronic post-stroke patients and healthy subjects.

The main questions it aims to answer are:

Does taVNS affect resting-state functional connectivity (measured by fNIRS) in chronic post-stroke patients?

Does taVNS affect resting-state functional connectivity (measured by fNIRS) in healthy subjects?

Are there differences in the effect of taVNS on functional connectivity between the post-stroke group and the healthy group?

Researchers will compare the effect of active taVNS (real stimulation) to a sham stimulation (control) to evaluate its specific impact on the brain's functional networks.

Inclusion Criteria for post-stroke participant:

• age 18 or older
• Right-handed participant;
• Hemiparesis in the chronic phase (>6 months post-stroke)
• Participant who has agreed to sign an informed consent form;
• Participant who is affiliated with social security.

Inclusion Criteria for healthy participant:

• age 18 or older
• Right-handed participant;
• Participant who has agreed to sign an informed consent form;
• Participant who is affiliated with social security.

Exclusion Criteria for post-stroke participant:

• Allergy to neoprene (the material used to make the fNIRS cap);
• Hair volume preventing the cap from being put on and/or access to the scalp;
• Cognitive impairment making it impossible to participate in the study;
• Phasic disorders preventing understanding of instructions and effective communication;
• Pregnant or breastfeeding women;
• Persons under legal protection

Exclusion Criteria for post-stroke participant:

• Allergy to neoprene (the material used to make the fNIRS cap);
• Hair volume preventing the cap from being put on and/or access to the scalp;
• Pregnant or breastfeeding women;
• Persons under legal protection