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In a coma, there is no spontaneous organized behavior or even a response to irritating stimuli. Patients in a persistent vegetative state (PVS) are like those in a coma, except that they don’t seem asleep: Their eyes are open and move. In a minimally conscious state (MCS), occasional signs of arousal and organized behavior occur. Some patients in a PVS progress to an MCS: Functional magnetic resonance imaging studies indicate that these patients have function in some of the cortex (Journal Watch Mar 29 2007).
One theory of MCS holds that the cortex may be preserved but rendered inactive by a lack of stimulation from the thalamus. Neurologists tested this hypothesis in a 38-year-old man who had remained in an MCS for 6 years following a traum…