I was born half-strangled and spent the first minutes of my life without oxygen. I remember none of it, of course. What I know about clinical death from other causes comes from several dozen reports I have read and cross-checked.
The near-death experience (NDE) is one of those phenomena where believers in the paranormal and materialists dug their trenches long ago and have been shooting at each other ever since. Hardly anyone on that field speaks in a calm voice. Let me try.
What is actually observed
The classic NDE runs like this: leaving the body, moving through a tunnel, light, meeting relatives who have died, a life review, the return. Not everyone has one. It happens to a small but steady share of people who survive cardiac arrest or another brush with death: depending on the study, 9 to 18 percent of cardiac-arrest survivors report some form of NDE (van Lommel, 2001; Parnia et al., 2014).
The phenomenon itself is well documented. The trouble starts with its interpretation.
What neuroscience says
Several neurobiological mechanisms are known today, and each explains some part of the NDE.
— Hypoxia and reperfusion. Starved of oxygen, neurons in the visual cortex begin to fire chaotically, and from the inside this looks like a tunnel with light at the end (Blackmore, 1993).
— DMT and endogenous psychedelics. Rick Strassman suggested that the dying brain releases its own DMT. This has not been confirmed in humans, but DMT has been found in the rat brain, and its level rises during cardiac arrest (Dean et al., 2019).
— A gamma burst before death. Borjigin and colleagues recorded a brief surge of gamma waves in the final seconds, first in rats (PNAS, 2013) and later in a few dying patients (PNAS, 2023), strongest in regions tied to perception and memory. The brain lights up one last time, brighter than in ordinary life. This may be what lies behind the "hyper-lucid awareness" so many survivors describe.
— REM intrusion. Nelson and colleagues (Neurology, 2006) found that people with NDEs more often have episodes in which REM sleep breaks into wakefulness. Hence the hypothesis that an NDE is a kind of dream set off under extreme conditions.
No single mechanism explains the NDE as a whole, but put together they account for most of what survivors report.
What neuroscience does not know
This is where the line runs.
Reports of accurate details of the resuscitation, seemingly seen "from above" (the literature calls them veridical perceptions), are methodologically hard to work with. Pim van Lommel (Lancet, 2001) assembled a Dutch cohort of 344 patients; 18 percent reported NDEs, some with verifiable details. But the AWARE study (Parnia et al., 2014), designed specifically to test perception "from above", gave a modest result: of 101 patients interviewed, only one recalled an event that could be independently checked.
That result does not allow us to call veridical perceptions a myth. Their rarity and the failure to reproduce them do call for caution.
The long-term personality changes are also an open question. Many NDE survivors say their values shifted, their fear of death faded, their attitude to work changed. This can be tested statistically, and the tests confirm it. But it is explained well enough without any "contact with another reality": this is what post-traumatic growth looks like, a personality reorganising itself after an extreme experience.
What I think
I sort my own conclusions into three levels of confidence.
Established: the NDE is a real neurocognitive phenomenon with a characteristic phenomenology. It occurs in 9–18 percent of cardiac-arrest survivors and changes personality for the long term.
Preliminary: part of the phenomenology (the tunnel, the light, the life review) is explained by known neurobiological mechanisms. The terminal gamma burst is the most promising lead on "hyper-lucid awareness".
Speculation: veridical perceptions, if they really exist, may point to something beyond the standard model of consciousness. Or they may be an artefact of memory, assembled after the fact from scraps of information. Right now the only honest answer is "I don't know".
In Neural Cosmology, the NDE is an interesting boundary case. If consciousness is information processing in a local node of a larger network, what happens when the node leaves the network? The standard answer: the process stops. The non-standard one: for a brief moment the node loses its "filter" and sees what is normally out of its reach.
Which answer is right, I do not know. And for as long as that "I don't know" stands, I keep the door ajar. Only ajar, so that no draught blows in from the office next door, where "contact with spirits" is sold for $150.