The author suggests a possible explanation: “Scientists realized that virtually all of the features of an NDE—a sense of moving through a tunnel, an out-of-body feeling, spiritual awe, visual hallucinations, intense memories—can be reproduced with a stiff dose of ketamine.”
Ketamine is actually a horse tranquilizer. It seems farfetched to suggest that we all have in our brains a secret stash of a drug like a horse tranquilizer, waiting for the moment of death to be released. But let's look further at this idea before dismissing it too fast.
The claim sometimes made about ketamine by NDE skeptics is that all (or virtually all) of the features of a near-death experience “can be reproduced” by using ketamine. But even if such a statement is true (and it probably isn't), such a statement might not mean too much. It could be that the users of the drug have a thousand and one freaky far-out experiences, and that if you cherry pick elements from a wide variety of accounts, you can piece together something resembling a near-death experience.
In this thread users of ketamine report their experiences, which include the following: closed eye visuals; sensations of being able to squeeze your fist out of existence; spatial distortions (such as shrinking rooms); mental peeking (being able to sense thoughts or feelings of others); language disintegration (hearing words that make no sense); the mind reeling with images of sex; comprehension lost; feelings of interconnectedness; time warp; “fuzzed” sensations; digitization (“Your cat walks past and the whole event happens in 8 distinct still frames one second apart”); dreamlike feelings; flesh rippling; sliding of furniture; deja vu (you think you have previously experienced whatever you are now experiencing); thought echo (your thoughts reverberate like echos); “2-dimensionalism” (in which everything seems flat); feelings of moving or contorting in space; coming back to the wrong place (“at its most extreme, re-entering your own body, but being convinced that it is the body of an alien in another, different reality”); roller-coaster sensations; visions of alien worlds.
All in all, this list is not a very good match to typical accounts of near-death experiences, although it is possible to cherry-pick particular elements and say that several aspects of near-death experiences “can be reproduced” by using ketamine.
Another web site listing ketamine experiences is here. 47 accounts are listed as “difficult experiences,”17 are listed as “bad trips,” 15 are listed as “train wrecks and trip disasters,” 30 are listed as “mystical experiences,” and 63 are listed as “glowing experiences.” Here are some random comments from the experiences listed as mystical experiences:
Everything lost its meaning
I was experiencing every emotion at once
An atomic bomb went off in my head
Total utter darkness for what seemed like forever
A feeling of living other people's lives
A feeling your body is gradually dissolving
A feeling of transcending your body and then returning to it
In a roller-coaster ride in a multidimensional giant fractal for eternity
A sensation of feeling colors
The essence of my husband and cat blended in with me and we all became one
I was floating around the Fourth Dimension
How it feels to use ketamine
I read the 30 accounts listed as “mystical experiences,” which is the subset that should be most likely to resemble a near-death experience. None of the experiences strongly resembled the accounts given by those who claim to have had near-death experiences. Almost all of the accounts had numerous dreamlike rapid-change hallucinatory elements not found in typical near-death experiences – “acid trip” type of things. Only one of the 30 accounts mentioned a tunnel (a common element in near death experiences), but that tunnel led not to some glowing "Being of light" (as in a near-death experience), but to a vision of a pool party.
"Pulled Through the Tunnel" -- a depiction of
a common element in a near death experience
Some ketamine trippers did report seeing a glowing light, and some identified the light with God, but I suppose if you've taken a strong enough drug, a nearby lightbulb might look like God. Those who have near death experiences often report a strong intuition or feeling of benevolence or love coming from the mysterious glowing light they see, but I read no such accounts by the ketamine users (although there were several along the lines of “I saw this bright light, and I thought, wow, that must be God.”) I don't remember any of the accounts mentioning a sight of dead relatives (a common element of near-death experiences). A large fraction of those who claim near-death experiences seem to remember a kind of “life review.” While at least one ketamine user claimed to relive every experience he had ever had, such an experience (or an experience of “life review”) seems to be a very rare element of ketamine experiences.
Quite a few ketamine users reported being in some sense disassociated from their body (something like “beyond their body,”), as one might experience during a heavy drug trip. But in the 50 or so accounts I read, there seemed to be no users who reported floating above their bodies and looking down on them, a common element of near-death experiences.
In summary, while ketamine drug trips sometimes have some parallels with near-death experience, the typical experiences of these drug users seems to be something very different from the reports of near-death experiences, without any close similarity. One scientific paper (Corazza, 2010) reported several dozen ketamine users with experiences similar (in some ways) to near-death experiences, but the paper did not use a random sample of ketamine users – instead it specifically recruited or advertised to find ketamine users with such NDE-like experiences (which means that it gives us no idea of what fraction of ketamine users have such experiences).
But perhaps there is some other type of drug in our brains released at the moment of death – not ketamine, but something like it. There is a problem with the idea, however. We could not explain the origin of such a thing from any evolutionary standpoint, as it would have no survival value. Natural selection is only interested in giving us things that help us live long enough until we reproduce. Evolution and natural selection have not the slightest preference for whether we might have pleasant experiences at the moment of death. And if we did have in our brains some “secret stash” of something like a hallucinogenic drug or chemical released at the moment of death, we would expect that it would also be released at less traumatic moments, such as a non-fatal moment of enormous injury. But there is no evidence that any such drug or chemical is released when people have horrible non-fatal injuries.
It would seem, therefore, that there is not yet a drug that adequately explains near-death experiences. I can imagine, however, that future researchers will test various hallucinatory drugs for the sake of finding one that closely matches a near-death experience. It may not get them very far in terms of plausibly explaining the phenomenon of near death experiences, but it will no doubt be a lot more fun than classifying rare species of insects or working on quantum mechanics calculations.