NEW YORK - The brain's tendency to sometimes blur the line between sleep and waking may help to explain near-death experience, research suggests.
It has been an open question why some people see bright light, feel detached from their bodies or have other extraordinary sensations when they are close to
dying or believe they may die.
Some people view these so-called near-death experiences as evidence of life after death, and many neurologists have considered the phenomenon too complex for scientific study.
But the research published in the journal Neurology suggests the blending of sleep and wake states as a biological cause of near-death experiences.
Researchers found that adults who said they had had such an experience were also likely to have a history of REM intrusion - where aspects of the dream state of sleep spill over into wakefulness.
People may, for example, feel paralysed when they first wake up, or have visual or auditory hallucinations as they fall asleep or awaken.
Of the 55 study participants who had had a near-death experience, 60 per cent had also experienced REM intrusion at some point in their lives, compared with 24 per cent of a comparison group.
The findings suggest that the brain's arousal system predisposes some people to both REM intrusion and near-death experience, say the study's authors, led by Kevin R. Nelson, a neurologist at the University of Kentucky in Lexington.
This arousal system, says Dr Nelson, regulates not only REM sleep, but also attention and alertness during waking hours - including during dangerous situations.
And many of the features of REM intrusions, he says, parallel those of near-death experience.
During REM sleep, visual centres in the brain are highly active, while the limb muscles are temporarily paralysed. So REM intrusion during peril could promote the visions of light and sensation of "being dead" that people often have during a near-death experience.
An important fact, Dr Nelson notes, is that stimulation of the vagus nerve, which connects the brain stem to the heart, lungs and intestines, triggers REM intrusion. And heightened activity in this nerve is sure to be part of the body's response to danger.
- REUTERS
