Inclusion Criteria:  right-handed signed informed consent form medical, neurological, neuroradiological healthy social security number use of contraception for female subjects  Exclusion Criteria:  standard contra-indication for MRI examination (pacemaker, metallic implants/dental braces, claustrophobia, pregnancy) chronic drug or alcohol user cognitive disorders linked to cardiovascular accidents chronic neurological or psychiatric disorder history of major illness (diabetes, metabolic, cancer, immunological) use of medicines that can potentially interfere with cerebral imaging (psychotropic drugs, hypnotics, anxiolytics, neuroleptics, anti-parkinson drugs, benzodiazepines, steroidal anti-inflammatory drugs, antiepileptics, anti-histamines, central analgesics and muscle relaxants) dyschromatopsia pregnant female non-MRI compatible tattoo