Analyse de l'activité cérébrale intrinsèque Pendant le Coma et Lors du Retour à la Conscience

Several studies in healthy volunteers have suggested that the synchronized functional connectivity in the DMN (Deafult-Mode Network) would sustain the mental content at rest, and when required, a switch in the activity between the DMN and other networks involved in specific congnitive functions, would occur. This interaction permit to make the hypothesis, that baseline brain activity is likely to shape our ongoing " stream of consciousness " and could correlate with conscious perception. The investigators hypothesized that DMN connectivity strength would be related to the level of consciousness of brain-damaged patients. The investigators will follow severely brain-injured patient in coma. Clinical examination using standardized behavioural scales: FOUR score (Full Outline of UnResponsivess), Coma Recovery Scale-Revised); and brain imaging assessesments using MRI (functional and anatomical connectivity, cortical thickness) will be performed at: 3 to 30 (visit 1), and 60 (visit 2) days after insult. If patient recover a normal conscious state between 30 and 60 days, an additional clinical and brain imaging assessment will be performed to identify related changes in brain activity (visit 1*) Monitoring of vital parameters will be performed in patients by a senior anaesthesiologist throughout the experiment.