to infinity and back: Near-Death Experiences a function of "REM intrusion?"

This week's NewScientist includes a fascinating (subscriber-only) article on Near Death Experiences, or NDEs. Kevin Nelson, a Kentucky neurophysiologist, implicates "REM intrusion" in the bizarre hallucinations and ethereal oogly-googlies common to the event. Excerpts below:

A study in 1990 at the University of Virginia Health Sciences Center in Charlottesville of 58 people who had experienced NDEs found that half would have survived without medical care. Sometimes fainting can be enough to trigger NDE-like sensations.

Nelson says that that's because despite the name, NDE has little to do with actually being close to death. He argues that the experience stems from an acute bout of "REM intrusion" - a glitch in the brain's circuitry that, in times of extreme stress, may flip it into a mixed state of awareness where it is both in REM sleep and partially awake at the same time....

Could REM intrusion also explain NDE? "Elements of near-death experience bear uncanny similarity to the REM state," says Nelson. Falling and floating - common in dreams - also occur in NDEs. And although normal dreams fade quickly from memory, that quirky combination of dreaming and wakefulness causes people with narcolepsy to recall their hallucinations vividly. They may remember their NDEs in such clear detail for the same reason, says Nelson. Meanwhile, total paralysis - a hallmark of REM - might make a person believe they really are dead....

Watching from the ceiling as surgeons work on one's body can be especially convincing during an NDE. Olaf Blanke, a cognitive neurologist at the Swiss Federal Institute of Technology in Lausanne, says these sensations happen when the brain fails to weave different threads of sensory information together. If tactile senses tell the body it is lying down, but a wobbly inner ear causes vision to be interpreted as though from a floating perspective, then a person may well "see" themselves from the ceiling. Blanke has caused people to see their disembodied legs from a floating perspective by electrically stimulating the angular gyrus, a brain area that integrates sensory information. A mixed REM state could disrupt the integration of sensory information in much the same way, says Blanke. The brain may be aware, but the transfer of sensory and motor information from the body is largely shut down....

To investigate the possible link between REM and near-death experiences, Nelson surveyed the frequency of REM intrusion among 55 people who had NDEs in a variety of circumstances, including fainting, heart attack, traffic accident, lightning strike and during surgery. He compared them with 55 healthy volunteers who were matched for age and gender. The results were striking. Around 60 per cent of the NDE group reported having experienced symptoms of REM intrusion, either before or after their NDE, compared with just 24 per cent of the control group. What's more, REM intrusions in the NDE group were more elaborate, including not just sleep paralysis but also hallucinations (Neurology, vol 66, p 1003). "This is good preliminary evidence," says Nelson.

As we all know, time dilates when we dream, so if NDEs are souped-up existential daydreams, Nelson's hypothesis accounts for flat brainwaves that largely accompany them.

Nelson hopes to continue researching the phenomenon, and figure out a way to artificially spur a Near Death Experience. Neuroscientists, two words:

Pop quiz.