Effect of Transcutaneous Auricular Stimulation of the Vagus Nerve on Functional Connectivity in the Brain at Rest

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.