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In 1991, Atlanta, Ga. resident Pam Reynolds had a near-death experience (NDE). Reynolds underwent surgery for a brain aneurysm, and the procedure required doctors to drain all the blood from her brain. Reynolds was kept literally brain-dead by the surgical team for a full 45 minutes. Despite being clinically dead, when Reynolds was resuscitated, she described some amazing things. She recounted experiences she had while dead -- like interacting with deceased relatives. Even more amazing is that Reynolds was able to describe aspects of the surgical procedure, down to the bone saw that was used to remove part of her skull [source: Parker].

­Courtesy StockXchng­ It is estimated that as many as 18 percent of people who have been resuscitated after cardiac arrest have reported a near-death experience.

What's remarkable (although not unique) about Reynolds' experience is that it is the combination of an NDE and an out-of-body-experience (OBE). HowStuffWorks has braved this territory on the edge of reality, explaining how near-death experiences work and how a person can have an out-of-body experience. Science, too, has made its own headway toward explaining these weird phenomena. Two studies on the separate aspects of Reynolds' experience were conducted in 2007. Each seems to explain how a person can have an OBE or a NDE, but do they hold up in explaining experiences like Reynolds'? ­­

As many as 18 percent of people brought back from death after a heart attack said they'd had a NDE [source: Time]. While many religious adherents might not be surprised by these accounts, the idea that human consciousness and the body exist distinctly from each other flies in the face of science. A brain-dead person should not be able to form new memories -- he shouldn't have any consciousness at all, really. So how can anything but a metaphysical explanation cover NDEs?

A study from the University of Kentucky has quickly gained ground among scientists as possibly the best explanation for NDEs. Researchers there theorize that the mysterious phenomenon is really an instance of the sleep disorder rapid eye movement (REM) intrusion. In this disorder, a person's mind can wake up before his body, and hallucinations and the feeling of being physically detached from his body can occur.

The Kentucky researchers believe that NDEs are actually REM intrusions triggered in the brain by traumatic events like cardiac arrest. If this is true, then this means the experiences of some people following near-death are confusion from suddenly and unexpectedly entering a dream-like state.

This theory helps explain what has always been a tantalizing aspect of the mystery of NDEs: how people can experience sights and sounds after confirmed brain death. The area where REM intrusion is triggered is found in the brain stem -- the region that controls the most basic functions of the body -- and it can operate virtually independent from the higher brain. So even after the higher regions of the brain are dead, the brain stem can conceivably continue to function, and REM intrusion could still occur [source: BBC].

This sounds like a good explanation for NDEs, but what about OBEs? Are they the same thing?

The Temporal Parietal Junction and OBEs

While the REM intrusion theory for near-death experiences explains the apparent hallucinations that accompany NDEs, another aspect remains a mystery. How can a person watch his body after he dies? Though out-of-body experiences are sometimes reported as part of the near-death experience, they can also stand alone, indicating that they are a different animal than NDEs.

Photo courtesy Dreamstme Research shows that different parts of the brain are most likely responsible for out-of-body experiences and near-death experiences.

patient's seizures, This is supported by a bit of accidental research. To find the cause of a 43-year-old epilepticSwiss neurologist Dr. Olaf Blanke conducted a brain mapping test using electrodes planted on the brain to determine which area controls what function. As one region was being stimulated, the woman had a sudden out-of-body experience. She told Blanke that she could see herself from above [source: New York Times].

Blanke determined that by electrically stimulating the woman's angular gyrus, a part of the temporal parietal junction, he could induce her OBEs. What's remarkable is that the patient experienced an OBE each time her angular gyrus was arbitrarily stimulated.

At any given time, the brain is assaulted with information. As a result, we become desensitized to the sights and sounds around us, such as the buzz of a fluorescent light. The temporal parietal junction (TPJ) is responsible for sorting through this disparate information and putting it together into a coherent package.

The TPJ also happens to be the region that controls our comprehension of our own body and its situation in space. Blanke believes that a misfiring of this region is responsible for OBEs. If any of the information being sorted by the temporal parietal junction becomes crossed, like where we are in space, then we could seemingly be released from the confines of our body -- even if only for a moment.

Both Blanke's and the University of Kentucky theories explain OBEs and NDEs. But what about when you put the two together as an explanation for experiences like that of Pam Reynolds? This still does not resolve how Pam Reynolds and others like her view themselves outside of their bodies while they were brain-dead.

NDEs may be a result of REM intrusion, triggered in the brain stem. But OBEs are controlled by a region of the higher brain, which is clinically dead when NDEs occur. What's more, it seems logical to believe that the higher brain must still function in order to interpret the sensations produced by the REM intrusion triggered in the brain stem.

Even though combining the University of Kentucky and Blanke theories does not produce an explanation for NDEs, it does not mean that either theory is wrong. Research in one area often leads to a breakthrough in another. Perhaps we will find out that an organic function is indeed behind NDEs.

If neurology does come up with the definitive explanation for NDEs, the mystery may still remain. Science could explain the "how," while leaving the "why" unanswered. Discovering an explanation for NDEs may reveal a door to the metaphysical world, which could possibly be unlocked -- and explored -- by science.

As physician Dr. Melvin Morse wrote, "Simply because religious experiences are brain-based does not automatically lessen or demean their spiritual significance. Indeed, the findings of neurological substrates to religious experiences can be argued to provide evidence for their objective reality" [source: Morse].