Cerebello-motor Neuromodulation After Stroke. CERSTIM.

PATIENTS Inclusion Criteria: * Male or female aged 18 years or older on the day of inclusion. * Affiliated with a social security system, Universal Health Coverage (CMU), or any equivalent scheme. * Ischemic stroke or intraparenchymal hematoma that occurred more than 6 months ago, with no upper time limit. * Motor deficit of the upper limb confirmed by the ARAT scale, with the ability to grip and press on a tablet. * stroke lesion not affecting the motor cortex in the hand knob area. Exclusion Criteria: \-- Pregnant and breastfeeding women * Total paralysis of the affected hand * Conditions that are life-threatening or could compromise follow-up during the study period * Contraindications to MRI and tACS (ferromagnetic surgical clips, ocular implants, intraocular or nervous system metallic foreign bodies, implants or metallic objects likely to concentrate the radiofrequency field, cochlear implants, brain or cardiac stimulators, presence of a craniotomy scar) * Participation in another biomedical study focused on motor or overall recovery during the same period, or current exclusion period from another biomedical study HEALTHY Inclusion Criteria: * Male or female aged 18 years or older on the day of inclusion. * Affiliated with a social security system, Universal Health Coverage (CMU), or any equivalent scheme. Non inclusion criteria \-- Pregnant and breastfeeding women * Conditions that are life-threatening or could compromise follow-up during the study period * Contraindications to MRI and tACS (ferromagnetic surgical clips, ocular implants, intraocular or nervous system metallic foreign bodies, implants or metallic objects likely to concentrate the radiofrequency field, cochlear implants, brain or cardiac stimulators, presence of a craniotomy scar) * Participation in another biomedical study during the same period, or current exclusion period from another biomedical study