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That's a point the University of Virginia's Greyson wanted to settle. Are NDErs up there on the ceiling or aren't they? In 2004, he began a study that he hoped would provide the answer. At the university's electrophysiology clinic, surgeons implant cardioverter-defibrillators in patients at high risk of sudden death. In the process, cardiac arrest is induced. Greyson arranged for a laptop computer, displaying a series of images, to be stationed near the ceiling, where only an elevated being could see the screen. As ingenious as it was, the investigation flopped. Greyson and his team reported last December that while cardiac arrest had been induced in 52 patients, none reported leaving his or her body.
Considering the incidence of NDEs, the result surprised Greyson. "But we can still learn from that failure," he says. "Unexpected findings like those tell us we don't understand NDEs as well as we thought, and that increases my enthusiasm for studying them."
What science has lacked until recently is an overarching theory that might explain why NDEs seem so coherent. In two articles published in Neurology, the second in March, a team of University of Kentucky researchers led by Nelson proposed that NDEs occur in a dream-like state brought on when crisis in the brain trips a predisposition to a type of sleep disorder. It's an hypothesis that's quickly gathered heavyweight support: "I think Dr. Nelson's REM-intrusion theory to explain NDEs is the actual physiologic explanation," says Minnesota sleep expert Mahowald.
His what theory? REM (rapid eye movement) sleep is the relatively active brain state in which most dreaming is thought to occur. REM intrusion is a disorder in which the sleeping person's mind wakes up before his body does. He feels awake, yet the muscle paralysis of REM can remain; he may also hallucinate until mind and body get back in sync. "Lay people think you're either awake or asleep," says Nelson, "but you needn't go directly from one to the other."
Some years ago, while studying first-hand accounts of NDEs, Nelson read the story of a woman whom medical staff had written off as dead and whose attempts to protest were thwarted by paralysis. Paralysis? As happens in REM intrusion! The seed of a new theory — that there was a link between REM and NDEs — grew in Nelson's mind.
He tested it by comparing the frequency of REM intrusion in 55 people who'd had NDEs with 55 controls. The results were striking: 60% of the first group reported some history of REM intrusion; 24% of the second. Nelson postulates that both REM intrusion and NDE involve a glitch in the arousal system that causes some people to experience blended states of consciousness. He stresses that he doesn't consider NDEs to be dreams, rather that the NDEr "engages through the REM mechanism regions of the brain that are also engaged during dreaming" — regions that infuse both dreams and NDEs with emotion, memories and images.
Nelson's theory goes some way toward explaining how NDEs can seem to occur when the brain is down. The sleep/wake switch is in the brainstem, which helps control the body's most basic functions and stays active for longer than the higher brain in cardiac arrest. "It's likely that the transition to brain death is, in fact, gradual," says Mahowald, "and NDEs occur during this transition." As for people reporting accurately on events that went on around them while they were apparently unconscious, Nelson says "they may be seemingly out of it but still processing in a very aberrant way."
Nelson's theory has been picked apart by two veterans of the field who could be said to favor a more spiritual view of NDEs. In a recent issue of the Journal of Near-Death Studies, Americans Jeffrey Long and Janice Miner Holden argue that since 40% of NDErs in Nelson's study denied ever having had an episode of REM intrusion, the idea that it underlies NDEs "seems questionable at best."
Happy to concede that "the brain deals with crisis in ways we don't fully understand," Nelson is keen to test his theory some more. He won't go into details, but it's believed he wants to monitor REM activity in subjects he would expect to have NDE-like symptoms in certain conditions.
Other researchers have their own ideas about how to solve the puzzle. Neuroscientist Blanke calls for "more work with imaging to investigate the brain functioning of large numbers of people who've had an NDE." Says Jansen, who'll soon release work comparing accounts of spontaneous NDEs with ketamine-induced ones: "We're moving on an exciting path. But nobody knows if we've made huge progress or just a little."
On balance, it's almost certain that NDEs happen in the theater of one's mind, and that in the absence of resuscitation, it's the brain's final sound and light show, followed by oblivion. Nonetheless, there's still no definitive explanation. There mightn't be a ghost in the machine. But it's a machine whose complexities remain well beyond our grasp.