Study on Cognitive Disorders of Multiple Sclerosis

Inclusion Criteria: * Remitting Multiple Sclerosis defined by Mc Donald et al., 2001 * Patient with authorised immunomodulator treatment or oral immunosuppressive therapy during more than three months: Bétâ Interferon, glatiramer acetate, azathioprine, methotrexate, mycophenolate mofetil, treatment by monoclonal antibody I.V. or anti-VLA4, natalizumab (Tysabri) * Patient having benefited, possibly, of following treatments : mitoxantrone, cyclophosphamide, cyclosporine, general-purpose immunoglobulins, only if the treatment is ended more of 6 months before the inclusion. * EDSS score ≤ 5.5 * DRS score ≥ 130 * PASAT 3s score \> 15 and \< median / control subjects according to 2 age brackets, sex, school level. * Signed the informed consent form. * Effective contraception for women in age to procreate Exclusion Criteria: * Progressive form MS * MS relapse of less of 4 weeks. * IV or oral corticoid treatment in the month preceding the screening * Medicinal treatments or non medicinal in cognitive or psychology-stimulant aim in the 3 months before the screening * Tumoral form MS visible in the MRI. * Depressive syndrome (MADRS score \> 19). * Quite other diagnosed psychiatric pathology * Known allergy or quite contraindication in memantin : renal or hepatic insufficiency, turned out epileptic disease, treatment by ketamine, amantadin, dextromethorphan, L-Dopa, dopaminergic agonist, barbituric, neuroleptic, 3,4-diaminopyridine, lithium, cimetidine, ranitidine, procainamide, quinine, nicotine, hydrochlorthiazide and ally, phenytoin, modafinil. * Recent treatment (less of 4 weeks) by antidepressants and/or anxiolytics. * Pregnancy or feeding. * Minor or Major "protected by the law" patient * Uncontrolled diet. * Patient having benefited of one psychometric assessment(including in particular tests planned in the protocol) since less of one year.