Evaluation will be performed at baseline, after 4 months (end of treatment period) and after 8 months. Evaluation will include clinical testing, cognitive battery (paper/pencil and computer tests), cognitive ecological evaluation (Computer test of attention in a virtual reality environment and driving test on a driving simulator), questionnaires about daily life and MRI (fMRI and MRI). All patients and healthy subjects will undergo the fMRI protocol using a paradigm previously published by the investigators group (Bonnet et al., 2009): Go/No-go paradigm with increasing difficulty during four successive conditions (the Tonic Alertness task, Go/No-go (IG), reversal Go/No-go (RG), and complex Go/No-go (CG). In a previous study the investigators observed compensatory activation in MS patients as compared to healthy controls for the three first conditions and a saturation of compensatory processes for the more complex. In the present study, the investigators hypothesize that a similar pattern will occur at baseline and that cognitive rehabilitation will improve brain compensation at the fourth level of complexity.