Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease of the central nervous system. People with MS frequently suffer from cognitive and visual impairment. Moreover, patients rank cognition and vision as two of the three most valuable bodily functions, in addition to mobility. Here the investigator use the established backward masking paradigm to study structural and functional alteration at the sub-milimeter scale in ultra-high field MRI in order to decipher the different input-output loops associated with the preservation and alteration of cognition in MS.

To identify abnormalities in mesoscale input and output connectivity at structural and functional levels that differ between patients with and without cognitive impairment. To address this objective, the investigator will analyse and compare functional activations in the primary visual cortex and task-associated regions in our previous studies. Secondary objectives: To develop, improve and validate multimodal laminar imaging at ultra-high field strength (7T) in comparison to control subjects available in our database to identify and quantify focal impairment in MS.

This is a cross-sectional study. 40 patients (20 patients with a cognitive deficit at least 2 SD below the norm and 20 patients without cognitive impairment) will be explored by multimodal ultra-high field (7T) MRI. The protocol included task, resting FMRI (functional connectivity), diffusion tensor (structural connectivity) and anatomical sequences (lesions and atrophy). In addition, the investigator will analyse standard clinical assessments including a neuropsychological examination. To understand the mechanisms underlying neurodegeneration and adaptation, it is important to contrast physiological and pathological alterations. In addition to comparing cognitively preserved and cognitively impaired patients, the investigator aim to compare our participants to a representative normative dataset available in our database of healthy individuals.

Inclusion Criteria:

• Adult patients (>= 18 years of age) with MS defined according to the McDonald criteria 2017 (Thompson et al., 2018)
• For the group of patients without cognitive impairment: SDMT or PASAT >=0 (based previous clinical assessments)
• For the group of patients with cognitive impairment: SD SDMT or PASAT <= -1.5 (based based on previous clinical assessments) (Parmenter et al., 2007)
• Person without uncontrolled systemic disease such as cancer, autoimmune disease, liver failure, severe or untreated hypertension, conduction conduction disorder or severe rhythm disorder
• No one with chronic psychiatric illness, severe dementia syndrome demented syndrome.
• No contraindication to MRI examination (claustrophobia, metallic foreign bodies, pacemakers),
• A person with social security coverage,
• Person having read, understood and signed an informed consent after information

Exclusion Criteria:

• Pregnant women
• Other inflammatory demyelinating diseases of the CNS
• Usual contraindications for an MRI examination: claustrophobia, metallic foreign bodies pacemakers, severe renal insufficiency.