Inclusion Criteria for Parkinsonien patients:  Age> 18 years old Idiopathic Parkinson's disease meeting the diagnostic criteria as defined by Ward and Gibb (1990) Patients usually taking dopaminergic treatment. No cognitive deterioration with: a Montreal Cognitive Assessment (MoCA) score ≥ 26 Patient with Parkinson's disease in the advanced motor complications stage for which surgical treatment is being considered  Inclusion Criteria for healthy subjects  Age> = 18 years old Patient free from Idiopathic Parkinson's Disease No cognitive deterioration: MMSE (MiniMentalSate Evaluation)> 26  Exclusion Criteria for both parkinsonien patients an healthy volunteers:  Uncorrected altered visual acuity Dyschromatopsia (especially color blindness) Psychotropic treatment introduced or modified recently (<1 month) Wearing a pacemaker (Pace Maker or Implantable Defibrillator) Pregnancy (verified by a urine pregnancy test for women of childbearing age) Other central nervous system disease (other parkinsonian syndrome, epilesia, stroke, etc.) or peripheral Intracranial metal implants on the cephalic stage and cochlear implant Untreated progressive mood or psycho-behavioral disorder Severe and poorly controlled eczema  Exclusion criteria for Parkinson's patients only:  Significant and disabling abnormal movement, not allowing good acquisition of the EMG signal (tremors or dyskinesias) Wearer of a Deep Brain Stimulation device (CI at tDCS).