Scientists have found that people who have had near-death experiences often have unusual ongoing experiences related to the brain's sleep-wake system, compared to people who have not had a near-death experience.
A study published in the April 2006 issue of Neurology, the scientific journal of the American Academy of Neurology, compared 55 people with near death experiences to 55 people of the same age and gender who had not had near death experiences.
Near death experiences are often described by those who have experienced them as when the consciousness seems to leave the body upon reaching a state near death. People experiencing this state have reported a sensation of weightlessness, while being able to see and hear their surroundings.
The study defined a near-death experience as: "a time during a life-threatening episode of danger such as a car accident or heart attack when a person experienced a variety of feelings, including a sense of being outside of one's physical body, unusual alertness, seeing an intense light, and a feeling of peace".
The study found that people with near death experiences are likely to have less of a boundary between their sleeping and wakeful states, and experienced what the study calls "Rapid Eye Movement (REM) intrusion" states while the person was awake.
These states included the person feeling like they could not move upon waking up, hearing sounds just before falling asleep or just after waking up, or having sudden muscle weakness in the legs.
Of the people with near death experiences, 60 per cent reported having these REM intrusion states, compared to 24 per cent of people who had not had near death experiences.
These results could be explained in two ways. Either the near-death experience was a result of a person's consciousness really leaving their body, sometimes resulting in a permanent looser coupling between the consciousness and the body, making them more prone to having the REM intrusion states. Or, people who are predisposed to REM intrusion states in the first place may be more susceptible to "illusory" near-death or out-of-body experiences, which are actually a REM intrusion itself.
The feeling of being outside of one's body has been associated with near-death experiences, the REM state, and in the conditions of sleep paralysis, narcolepsy and seizures.
In these states rapid eye movement could be caused by the body's response to what the consciousness is actually experiencing. However, study author Kevin R. Nelson, MD, of the University of Kentucky in Lexington believes it is the other way around. "People who have near death experiences may have an arousal system that predisposes them to REM intrusion," he said. Dr Nelson says that the feeling of being surrounded by light could be based on the visual activity that occurs during the REM state.
During the REM state the muscles can also lose their normal tension. This could be explained by the consciousness losing its normal connection to the brain, and therefore losing control of the body. Or, as Dr Nelson proposes, the lack of muscle tone due to a REM intrusion could reinforce the "illusion" of death.
"During a crisis that occurs with REM state intrusion, this lack of muscle tone could reinforce a person's sense of being dead and convey the impression of death to other people," he said. So which came first, the REM intrusion or the near-death? The answer so far is uncertain, but further study on whether people with a near-death experience were already susceptible to the REM intrusion states before their near-death experience could give some clues.
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