"Spiritual Doorway in the Brain": The science of near-death experiences

Do animals have them, too? Why the white light? Can you really "return" from the dead? An expert explains

Published January 13, 2011 1:01AM (EST)

We've all heard about the bright white light at the end of the tunnel, but what's really going on in a "near-death experience"? That's what neurologist and medical doctor Kevin Nelson tries to uncover in his first book, "The Spiritual Doorway in the Brain: A Neurologist's Search for the God Experience."

Dr. Nelson is one of the world's leading researchers in the biology of near-death and other mystical experiences, and his fascinating book takes the reader from investigations of MRI studies of the brain to historical anecdotes and philosophical inquiry. Three decades of research led Dr. Nelson to a unique and unexpected conclusion about near-death experiences -- rather than arising from parts of the brain that are unique to higher cognitive functions, they actually involve the oldest, most primitive parts of our brain, and might also relate to having dreams while still awake.

What happens near death, and what does it have to do with God? To find out, Salon spoke on the phone with Dr. Nelson from the University of Kentucky Medical Center in Lexington.

First things first: What's the deal with the tunnel and the light?

The tunnel is easy to explain. Much of the near-death experience is caused by low blood flow to the brain and to the head. When this happens, the eye fails before the brain fails. The outside field of vision goes first, but the center is preserved until the very end, so you develop a tunnel-like sensation. This sensation is also common in people who are about to faint.

As for the light, when your eye loses blood flow, light might become all that you're capable of seeing. Another reason for the light is the REM system, which is the "rapid eye movement" state of sleep. When the eye and the retina shut down, the remaining control system for vision is the REM system -- this is why you can see things when you're dreaming, and this type of vision might be activated during a near-death experience and cause a person to see light.

U.S. News and World Report found that as many as 18 million Americans have had a near-death experience. Must you be on the actual verge of death for this to happen?

People don't realize that fainting -- a common experience -- produces symptoms very similar to a near-death experience. Most people who say they had a "near-death experience" were not actually near death, but their experience was the same as those who were. In one experiment, scientists actually induced fainting episodes in the test subjects, and many of them had an out-of-body experience while they fainted, which also commonly occurs during real near-death experiences. So in fact, many individuals know what it's like to have a near-death experience.

Some people who were close to death recall having a mystical experience -- they feel peace, love and unity with the world, or have pleasant encounters with deceased relatives. What accounts for these occurrences?

A near-death experience varies greatly from person to person. Some people experience rich narratives in which they meet spiritual beings and are given messages. Not everybody sees light, not everybody has a sense of euphoria -- some people actually have an unpleasant emotional response during the near-death experience. But what generally happens is the pleasure system of the brain is engaged. This happens with spiritual experiences in general. When the Russian novelist Dostoevsky faced execution and lived to tell about it, he related a story of ecstasy and spiritual awakening. The dopamine reward system seems to be activated when a person believes they are near death, and the REM system, counterintuitively, is also activated. Experiments have shown that if you destroy parts of the brain that support REM sleep, you also take away the effectiveness of the dopamine reward system. Many pieces of the puzzle are missing, but we know there's a connection. 

Your own research has led to a unique explanation for near-death experiences that you call the "REM intrusion hypothesis." Can you explain that?

When a person is in crisis, their body reacts to the threat, and the brain must be in the correct state of consciousness. When a primate on the savannas of Africa hears a lion's roar, it's very important to stay awake. This is so obvious that most people overlook how important it is for the brain to know when to be asleep or awake. This necessity is coupled with fight or flight survival reflexes. There's a switch in the primitive part of the brain that moves us from REM sleep to waking. The majority of the time, this switch works well. But it works better in some people than in others. If you have narcolepsy, it works poorly and you move quickly between the different states.

During REM sleep, the body is actually paralyzed. If a person wakes up and their brain doesn't move out of REM, they might be still paralyzed. This is called sleep paralysis. Hallucinations, activation of the visual system, out-of-body experiences and dreamlike images while a person is awake are probably all related to activation of the REM system when someone's awake. Now why does this happen when a person has very low blood pressure -- which occurs near-death -- or when someone is fainting? As it turns out, the body systems that regulate the transition between REM and wakefulness are also responsible for the body's reaction to low blood pressure. Why this happens is not clear, but it's deeply wired in the oldest part of our brains, so the connection must be doing something good for survival, and it must be important.

You described one patient, Jan, who had doctors operating on her liver, intestines and heart. She was near death, and though she was given drugs to put her to sleep, she was fully awake and felt the pain. Shortly before passing out, she saw a white light and her dead mother spoke to her. What was happening to her?

When a brain isn't getting enough blood flow, we move between consciousness and unconsciousness, and the transitions are not necessarily abrupt. The borders become fuzzy, especially if the rate of blood flow to the brain is changing a lot. So people can actually stay in that borderland for a long time. They might be on the gurney with their eyes closed, but they're actually awake. With REM intrusion, the REM state might be triggered when a person is awake, so while a person is in a borderland state caused by reduced blood flow, they also experience a second borderland state where the experiences of REM are transposed onto an awake state of consciousness. These dual borderland states might explain why there are so many aspects to the near-death experiences, like paralysis coupled with seeing light and experiencing strange narratives.

What's the difference between near-death and returning from death? What about people who are frozen for hours and then recover?

Returning from death is not something that people do. When a person drowns in ice water, the brain cells shut down and stop functioning, but they don't die. But when a person's heart stops, their brain cells burst after about five minutes. When the cells burst, they're dead and don't come back. If the cells are frozen instead, they don't burst, and when they warm up, they start functioning again.

Research shows that mystical experiences involve the most ancient parts of our brain, which implies that spirituality is not limited to humans. Do you think apes, dogs and other mammals are capable of spirituality?

I think they're capable of having the experiences that form human spirituality, which I'll define as the sense that you've touched some kind of divine. I'm not sure if an animal experiences this type of connection, and of course an animal can't communicate this to us, so the question will remain unanswered. But mammals do have the same parts of the brain that are triggered in human out-of-body experiences. If the temporal parietal lobe is activated in a monkey or dog or cat, there's no reason to believe that they don't experience something similar to what we experience. They most probably don't convert these sensations into a connection with something outside of themselves, because they probably don't have concepts or ideas like the ones that humans have. But might they experience tunnels and light? They probably do. Do memories come to them? I think they might. Can animals experience that mystical sense of oneness? That's intriguing to think about. We know that the sense of oneness comes through the limbic system, which is the emotional system of the brain that we share with other mammals. So it's possible.

How has the split between neurology and psychology affected research into near-death and out-of-body experiences?

For many years, neurologists and neuroscientists have scoffed at anything that has to do with subjective experiences. They're much more interested in looking at a cell under a microscope, but they're not interested in the experience of the mind. The psychiatric fields dealt with the mind, and the neurologists dealt with the brain. In recent years, this divide has changed, mostly because of new technologies that allow researchers in psychology to record what's going on in the brain, and then correlate these records with what a person describes about the subjective experience. I rely on well-established knowledge about mechanisms of the brain, but my understanding of the brain is more of a "systems" approach. Many disciplines think about the brain in terms of specific regions or particular chemicals, but to really understand the brain, you have to try to understand how everything interacts.

In your book, you say that you want to "explain the nature of spiritual experience, not explain it away." What do you mean?

The experiences that I write about are very powerful and have deep emotional and personal value, and I don't think they should be dismissed. I'm interested in a nonjudgmental inquiry into near-death or spiritual experiences, and because of this, people have told me things that they generally wouldn't confide to other kinds of researchers. I understand spiritual experiences in biological terms, but no matter how much we understand about how the brain is working, we won't know why it works in this way. There will always be a mystery to that. I'm interested in discovering the how, but ultimately the why is a much more interesting question.

Taking some types of drugs can initiate experiences that are very similar to what people experience near death. Are drug-induced feelings less genuine that those that occur spontaneously?

The experiences are nearly identical. If these drugs produce hallucinations or out-of-body experiences or profound spiritual insights, is it genuine? I have to fall back on the philosopher and psychologist William James, who said to judge experiences by their fruits, and not their roots. So the effects, not the causes, are what's important. Drugs produce spiritual experiences, and it's not for us to judge how genuine or real they are for the person who experienced them.

How do the culture wars about religion affect scientific research into spirituality?

You don't need to know how the brain is working in order to dismiss God, and knowing how the brain works doesn't prove or disprove a God. These are separate questions. Does evolution prove that God doesn't exist? I don't think so. Does it make it easier to explain consciousness in a Godless universe? Yes, but you can also conclude that there is no God without knowing anything about evolution or how the brain works. So my work is not on either side of that war. But on the other hand, I live in a state that has a creationist museum and that's about to erect a creationist theme park, and I don't expect to find my book on those bookshelves.

By Katherine Don

Katherine Don is a freelance writer in New York.

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