More recently, British writer Susan Blackmore received a report from a woman from Cyprus who had an emergency gastrectomy in 1991:
On the fourth day following that operation, I went into shock and became unconscious for several hours …. Although thought to be unconscious, I remembered, for years afterward, the entire, detailed conversation that passed between the surgeon and anesthetist present ….
I was lying above my own body, totally free of pain, and looking down at my own self with compassion for the agony I could see on the face; I was floating peacefully. Then … I was going elsewhere, floating towards a dark, but not frightening, curtain-like area …
Then I felt total peace. Suddenly it all changed—I was slammed back into my body again, very much aware of the agony again.
The underlying neurological sequence of events in a near death experience is difficult to determine with any precision because of the dizzying variety of ways in which the brain can be damaged. Furthermore, near death experiences do not strike when the individual is lying inside a magnetic scanner or has his or her scalp covered by a net of electrodes.
It is possible, though, to gain some idea of what happens by examining a cardiac arrest, in which the heart stops beating (the patient is “coding,” in hospital jargon). The patient has not died, because the heart can be jump-started via cardiopulmonary resuscitation.
Modern death requires irreversible loss of brain function. When the brain is starved of blood flow (ischemia) and oxygen (anoxia), the patient faints in a fraction of a minute, and his or her electroencephalogram, or EEG, becomes isoelectric—in other words, flat.
This implies that large-scale, spatially distributed electrical activity within the cortex, the outermost layer of the brain, has broken down. Like a town that loses power one neighborhood at a time, local regions of the brain go offline one after another.
The mind, whose substrate is whichever neurons remain capable of generating electrical activity, does what it always does: it tells a story shaped by the person’s experience, memory, and cultural expectations.
Given these power outages, this experience may produce the rather strange and idiosyncratic stories that make up the corpus of NDE reports. To the person undergoing it, the NDE is as real as anything the mind produces during normal waking.
When the entire brain has shut down because of complete power loss, the mind is extinguished, along with consciousness. If and when oxygen and blood flow are restored, the brain boots up, and the narrative flow of experience resumes.
Scientists have videotaped, analyzed, and dissected the loss and subsequent recovery of consciousness in highly trained individuals—U.S. test pilots and NASA astronauts in centrifuges during the cold war (recall the scene in the 2018 movie First Man of a stoic Neil Armstrong, played by Ryan Gosling, being spun in a multiaxis trainer until he passes out).
At around five times the force of gravity, the cardiovascular system stops delivering blood to the brain, and the pilot faints. About 10 to 20 seconds after these large g-forces cease, consciousness returns, accompanied by a comparable interval of confusion and disorientation (subjects in these tests are obviously very fit and pride themselves on their self-control).
The range of phenomena these men recount may amount to “NDE lite”—tunnel vision and bright lights; a feeling of awakening from sleep, including partial or complete paralysis; a sense of peaceful floating; out-of-body experiences; sensations of pleasure and even euphoria; and short but intense dreams, often involving conversations with family members, that remain vivid to them many years afterward.
These intensely felt experiences, triggered by a specific physical insult, typically do not have any religious character (perhaps because participants knew ahead of time that they would be stressed until they fainted).
By their very nature, NDEs are not readily amenable to well-controlled laboratory experimentation, although this might change. For instance, it may be possible to study aspects of them in the humble lab mouse—maybe it, too, can experience a review of lifetime memories or euphoria before death.