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The ascending reticular activating system (ARAS) is necessary for wakefulness, and the polymodal cerebral cortices (precuneus) are necessary for awareness. These authors tested the hypothesis that the vegetative state (VS) of wakefulness without awareness is caused by impairment of precuneus functioning along with normal functioning of the ARAS. They used positron emission tomography (PET) imaging to measure regional cerebral blood flow (rCBF) in 10 healthy controls and 10 VS patients (6 with VS caused by traumatic brain injury [TBI], 4 with VS caused by hypoxic-ischemic [H-I] damage). Coregistered magnetic resonance images aided interpretation of the PET images.
As expected, the VS patients had significantly lower rCBF than controls in the …