Sleep Homeostasis in the Vegetative and Minimally Conscious States

The EEG slow-wave activity (SWA) organization in temporal cycles with an exponential trend of attenuation over the wake- fulness-sleep cycle is thought to reflect synaptic homeostasis. Ten subjects in a vegetative state as a result of traumatic brain injury (n = 4) or anoxia-hypoxia were studied. Local SWA regulation, indicating restored homeostasis, was observed in three posttraumatic subjects, whose clinical condition developed into a minimally conscious state 3 to 6 months later. All subjects whose SWA regulation was incom- plete or undetectable were in a vegetative state 6 months after the study. This neurophysiological approach can provide additional infor- mation on the (residual) functional brain organization of subjects in vegetative or minimally conscious states and would allow differential diagnosis and early prognosis.