 With these basic concepts in view, it may be easier to contrast various states of permanent unconsciousness. (For a helpful overview, see Cranford 1995.) “Whole-brain death” or total brain failure involves the destruction of the entire brain, both the higher brain and the brainstem. By contrast, in a permanent (irreversible) vegetative state (PVS), while the higher brain is extensively damaged, causing irretrievable loss of consciousness, the brainstem is largely intact. Thus, as noted earlier, a patient in a PVS is alive according to the whole-brain standard. Retaining brainstem functions, PVS patients exhibit some or all of the following: unassisted respiration and heartbeat; wake and sleep cycles (made possible by an intact reticular activating system, though destruction to the cerebrum precludes consciousness); pupillary reaction to light and eyes movements; and such reflexes as swallowing, gagging, and coughing. A rare form of unconsciousness that is distinct from PVS and tends to lead fairly quickly to death is permanent (irreversible) coma. This state, in which patients never appear to be awake, involves partial brainstem functioning. Permanently comatose patients, like PVS patients, can maintain breathing and heartbeat without mechanical assistance.