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Our future, our universe, and other weighty topics


Thursday, May 7, 2015

Experiments Don't Shed Light on Near Death Experiences

Near death experiences (NDE) first came to public light in the 1970's with the publication of Raymond Moody's book Life After Life. Patching together elements from different accounts, Moody described an archetypal typical near-death experience, while noting that most accounts include only some elements in the described archetype. The archetype NDE included elements such as a sensation of floating out of the body, feelings of peace and joy, a life-review that occurs very quickly or in some altered type of time, a passage through a tunnel, an encounter with a being of light, and seeing deceased relatives.

A previous study on near-death experiences was published in the British medical journal The Lancet in 2001. The study interviewed 344 patients who had a close encounter with death, generally through cardiac arrest. 62 of those reported some kind of near-death experience. 15 reported an out-of-body experience, 19 reported moving through a tunnel, 18 reported observation of a celestial landscape, 20 reported meeting with deceased persons, and 35 reported positive emotions. More recently the AWARE study found some fascinating similar results, discussed here.

Some scientists have done experiments trying to shed light on near-death experiences. Back in 2014 we had the paper Surge of neurophysiological coherence and connectivity in the dying brain,” which was widely reported on by the press. But this was much ado about nothing, for this skimpy little study really did nothing at all to throw any light on near-death experiences.

The study did not involve human subjects, but merely involved rats. The scientists killed 9 rats who were connected to EEG machines that measure brain waves. The results, as show below, were not at all surprising: the brain waves quickly died out, reaching a very low level at about 17 seconds, and flat lining entirely by 30 seconds.



Trying to jazz up these dull-as-dishwater results, the scientists tried various minute statistical analytics to extract something that would be relevant to near-death experiences. Their data does not at all justify the title of their paper. They did not at all discover a “surge of neurophysiological coherence and connectivity in the dying brain.” To the contrary, their data shows brain activity very quickly dying out after the cardiac arrest of the rats they were studying, sharply declining by 7 seconds after the cardiac arrest, declining to very little at 17 seconds, and reaching nothing at 30 sec. They did not detect, on average, any spike in brain waves following cardiac arrest. An accurate title of their paper would have been Brain Function Very Quickly Disappears When Rats Die.

I may also note a few other points. First of all, it makes no sense to claim that a few seconds of brain activity could somehow correspond to what is reported in near-death experiences, since such accounts are elaborate accounts corresponding to at least several minutes of experience. Secondly, the sample size of the experiment was so small that no reliable conclusion can be drawn from it, because they only tested 9 rats. With a sample size that small, one can have little confidence in any results (just as asking 9 pedestrians whether they have cancer does not give a reliable indication as to how common cancer is).

Recently another study was released which has been touted as being relevant to near-death experiences. It has been called a follow-up of the previous study, but followed the same skimpy approach, using only 9 rats. Scientists killed 9 rats, and detected the release of more than a dozen neurochemicals. This result is trivial. The brain is releasing neurochemicals every minute.

But still, a scientist insinuates this ridiculously skimpy rat study tells us something about near-death experiences in humans:

According to Omar Mabrouk, research investigator of the Kennedy Group at UM, the euphoric perceptions commonly felt as revelations and second chances are most likely due to the excessive release of neurotransmitters during frantic brain-to-heart communication. "When you have these exaggerated amounts of neurotransmitters, like serotonin, there is a high likelihood that hallucinations would be an outcome,” Mabrouk said. “In addition to having positive moods and altered states of consciousness, there is a whole list of neurochemicals that are associated with mood and cognition.”

This is a most dubious speculation, and this claim of a “high likelihood” is unwarranted. There exists no proof that a short-term surge in neurotransmitters causes hallucinations, nor does there exist any evidence that any type of trauma can cause a visual hallucination within a few seconds, as would be required for hallucinations to produce near-death experiences after a cardiac arrest. It is widely believed that the electrical shock treatment called ECT produces a surge in neurotransmitters, but such treatment does not produce hallucinations.

What is the cause of hallucinations? Scientists don't understand this.  As a medical doctor states here, "The cause of hallucinations is unknown."

The fact that neurotransmitters may spike at death does nothing to suggest that such neurotransmitters are causing hallucinations in conscious organisms. The brain can continue to release neurotransmitters even after consciousness is lost. A previous study found that neurotransmitters increase in sheep which were killed by throat cutting. Evidently a spike in neurotransmitters can occur in completely unconscious organisms. Would we have any sound basis for concluding that these sheep hallucinated when their throats were cut? No, we wouldn't.  And to claim that such sheep had a "high likelihood" of near death experiences would be not merely unwarranted, but ridiculous. 

There are two general reasons for rejecting any hallucination hypothesis to explain near death experiences, whether or not that hypothesis involves neurotransmitters. The first reason is the time factor. Near-death experiences often occur in people who undergo cardiac arrest, something that should cause a quick loss of consciousness. In such cases there simply is no time for a substantial hallucination. People who have heart attacks don't go through a few minutes of raving that might correspond to hallucinations, and then lose consciousness. Instead they quickly have a heart attack and lose consciousness very soon thereafter. The second reason is that visual hallucinations produce random imagery, but the imagery in near death experiences is typically not random. It tends to have a few common themes like the themes mentioned at the top of this post.  This common pattern is not what we would expect from hallucinations. 

In the same vein of misguided experimentation, some scientists rigged up some elaborate perceptual trick involving an MRI scanner and cameras to fool people into thinking their body was located somewhere in the room elsewhere than it was. They then found that a part of the brain called the hippocampus lights up during such an experience. This silly study is being trumpeted as an explanation for the out-of-body experiences reported as part of near-death experiences (and in other cases also) – “your hippocampus causes it.” But such a study shows nothing of the sort, simply because you cannot explain a reported phenomenon by creating some special experimental situation totally different from the situation in which the phenomenon was reported.  People having near death experiences and out-of-body experiences don't have them in anything like the weird hi-tech setup that was used in this experiment.

I may also point out the whole “this brain part lights up when x occurs, so that brain part causes x” line of reasoning is generally bunk, as pointed out in the book Brainwashed: The Seductive Appeal of Mindless Neuroscience.

My suggestion to scientists who want to learn more about near-death experiences is to actually work with the people who have such experiences. Don't waste your time rigging up goofy camera configurations that don't match actual human experiences, and don't waste your time killing rats or cutting the throats of lambs.