Consciousness
Medical science argues that a permanent cessation of electrical activity indicates the end of consciousness. Those who view the neo-cortex of the brain as solely responsible for consciousness, however, argue that electrical activity there should be the only consideration when defining death. In many cases, especially when elevated intracranial pressure prevents blood flow into the brain, the entire brain is nonfunctional; however, some injuries may affect only the neo-cortex. During the death process, brain function can be lost gradually. When going through such a change, a small proportion of subjects have reported a variety of "near-death experiences".
Read more about this topic: Brain Death