What multiple sclerosis could bring to cognitive neuroscience?

The relevance of multiple sclerosis for cognitive neuroscience has evolved significantly during the last decades. After a relative and enduring disinterest, the 1980's has been marked by a first wave of studies aiming at characterizing the cognitive dysfunctions associated with this disease. Once identified, and grouped under the relatively vague and nonspecific concept of "subcorticofrontal syndrome", these cognitive symptoms had to wait until the end of the 1990's to give rise to a new and vigorous resurgence of attention. Interestingly, this genuine contemporary revival of interest originates in the promotion of the very same arguments that served until there to explain the weak investment of multiple sclerosis by neuropsychology and cognitive neuroscience. The early disseminated nature of brain lesions, their dynamic and unstable nature, the prevalence of white-matter lesions, and the alteration of non-modular aspects of cognition: all these arguments have discouraged neuropsychologists for a long time. Today, these very same specific properties of multiple sclerosis offer an extremely relevant model to explore cognitive dimensions of brain plasticity, to revivify the concept of disconnection in neuropsychology, and to evaluate some neuroscientific models of consciousness.