Motor Slowing and Its Lesion-related Correlates in Alzheimer's Disease

Inclusion Criteria: * Patients * Age between 40 and 85 * French mother tongue * Consulting at the Amiens Memory Resource and Research Centre (CMRR) for: * MCI, according to Albert et al.'s criteria (Albert et al., 2011) * Mild dementia (MMSE\>20) due to AD, according to McKhann's criteria (McKhann et al., 2011). * Mild dementia due to LBD, according to McKeith et al.'s criteria (McKeith et al., 2005). * Mild dementia due to FTLD, according to Rascovsky et al.'s criteria (Rascovsky et al., 2011). * Social security coverage * Healthy controls * Healthy age and gender matched volunteers will be recruited into the study from the general population. Exclusion Criteria: * Reading or writing difficulties related to a learning disorder or illiteracy. * A medical history with a potentially significant impact on cognition (non-corrected thyroid disorders or heart failure): * NYHA stage IV dyspnoea. * respiratory impairment requiring oxygen therapy. * liver impairment. * kidney failure, progressing neoplastic disease, or past or present alcohol abuse. * Past or present neurological disorders other than those having prompted consultation in the Memory Clinic: * stroke. * meningitis or encephalitis. * severe head injury. * sensorimotor impairments (sensory, proprioceptive, cerebellar and visual impairments). * epilepsy (requiring ongoing treatment), * psychiatric disorders (other than treated depression). * treatment with psychotropic medications (other than anxiolytics or antidepressant withdrawn or initiated in the previous month). Patients with parkinsonian syndrome were examined in the "on-drug" state. * Impossibility to perform a neuropsychological evaluation or brain MRI. * Withdrawal from the study at any time, if desired. * Pregnancy * Contra-indication to MRI: * nerve stimulators * cochlear implants * ferromagnetic foreign bodies close to nervous structures in the eye or brain * cerebral shunts * dental appliances * Legal guardianship or incarceration.