By LEE BOWMAN
Scripps Howard News Service
April 10, 2006
The study, published Tuesday in Neurology, the scientific journal of the American Academy of Neurology, found that people with near-death experiences are more likely to have a sleep-wake system where the boundaries between being asleep and being awake are less clearly regulated.
In particular, for many of them, the deep, rapid-eye-movement state of sleep often intrudes into times of wakeful consciousness. For instance, they wake up but feel they cannot move; just before falling asleep or just after waking up they hear sounds that no one else can hear; or they have sudden muscle weakness in their legs.
"These findings suggest that the REM state intrusion contributes to the near-death experience," said Dr. Kevin Nelson, a neurologist at the University of Kentucky in Lexington and lead author of the study. "People who have had a near-death experience may have an arousal system that predisposes them to REM intrusion."
Nelson and colleagues compared 55 people with near-death experiences with 55 people of the same age and gender who had not undergone such an episode.
For the study, a near-death experience was defined as a time during a life-threatening event, such as a car accident or heart attack, when a person had such sensations as being outside his or her physical body, unusual alertness, seeing an intense light or having a feeling of peace.
Various studies and polls suggest that up to 10 percent of the adult population has had at least one near-death experience.
Most of the research into the events has focused on documenting the most common aspects or verifying that people whose brain activity had seemingly ceased were able to recall events around them during that time after they revived.
But there have been more efforts recently to understand the physical underpinnings of the sensations. At least one other recent study found that there was altered function of the brain's temporal lobe in people who had near-death experiences, and also noted they had altered sleep patterns compared with people who had not had a close call with death.
In the neurology of those who had near-death experiences, 60 percent reported having a time of REM intrusion, compared to just 24 percent of those who had not had a near-death incident.
Nelson noted that several common features of near-death experience are shared with the REM state of sleep, including the feeling of being outside one's body, muscle tone loss or tension. And people suddenly roused from REM often report a feeling of paralysis. Narcolepsy and seizures are also linked to the REM state.
And, Nelson said, the feeling of being surrounded by light could also be based on visual activity that takes place during the REM stage.
Nelson noted that during a medical crisis that occurs with REM state intrusion, the associated lack of muscle tone "could reinforce a person's sense of being dead and convey the impression of death to other people."
He added that REM state intrusion is also associated with movement disorders such as Parkinson's disease.
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