Imagine heading toward a bright light, bathed in a warm peaceful glow, with past events floating through your wandering mind. Sounds like me heading out the front door for some fresh air during my drinking days.

But when experienced by those on the operating table or those being tended to by emergency medical technicians on the roadside, are these sensations caused by being near death or some other biological factor?

The former would suggest the possibility of an afterlife. Some persons have no doubt that such a cosmic destination awaits, but no amount of certainty in a conviction makes it so. A Muslim terrorist and hardcore atheist are equally certain what happens after death, but unshakeable belief has no bearing on the truth. So our goal today is to see if these experiences are explicable through what we know about anatomy & physiology and how the brain works.

Most attempts to study this issue have been tooth fairy science, where one tries to figure out specifics of a phenomenon before verifying that it exists. By necessity, these studies also favor anecdotes over data since there is no data to access. There is no scientific, testable, falsifiable evidence for post-mortem consciousness. There were even a few folks from those drinking days for whom evidence of pre-mortem brain activity seemed lacking.

While this is a difficult idea to research, an attempt was made by Dr. Penny Sartori. According to skeptic leader Brian Dunning, Satori put playing cards on top of operating room cabinets where they could be seen by a person from above but not by anyone who was laying back and being tended to by surgeons. There were 15 persons who had Near Death Experiences in the room, none of whom reported seeing the Queen of Hearts, Ace of Spades, or any lesser-known member of the deck.     

What they did report experiencing were NDE common features, such as becoming detached from the body, having one’s life flash before them, feeling a welcoming aurora, and, most ubiquitously, floating through a tunnel toward an embracing light. Some talked of seeing deceased loved ones or religious figures. Tellingly, the former looked how they did in old family photos, while the latter’s appearance matched how they are portrayed in artwork of the patient’s culture.

Conversely, there are also anecdotes about persons being overcome with terror or dread, and encountering monsters or demons. These tales are usually downplayed or completely ignored by most NDE proponents. They prefer these to be happy tales. Infrequently, there are religious fundamentalists who embrace these putative visions of hell since it bears out their holy book. But fundies in general do not seek confirmatory evidence outside the Bible. They dismiss the potential of alien life since it’s not mentioned in their scriptures, and the same reasoning causes them to dismiss the idea of a floating through a tunnel at life’s conclusion.  

While ecstasy, a life overview, beaming lights, and meeting with deceased persons have all been considered NDE hallmarks, Dunning writes that these also occur in persons whose brains experience high levels of carbon dioxide and/or decreased oxygen. He cited research in the journal Critical Care, which showed that more than 20 percent of heart attack patients who went into cardiac arrest and were resuscitated had high carbon dioxide levels, accompanied by these otherworldly experiences.

So were the visions and feelings caused by elevated CO2 levels or by their being nearly dead? Dunning wrote, “To find out which is the best correlation, we’d have to see whether an NDE can happen when one condition is present and the other is not.”

With that, he looked at research done on persons experiencing a loss of blood to the brain without risk of death. Such conditions were faced by fighter pilots placed in centrifuges in experiments to determine what happens under immense gravitational pressure. The pressure increased until the pilots lost consciousness, which happened once the brain began receiving insufficient blood. The pilots reported that while blacking out, they witnessed bright lights, floated through a tunnel, were detached from their body, and saw beautiful scenes, past events, and reconnected with departed loved ones, all while in a euphoric state. In short, it was an NDE’s carbon copy. That I can make such a dated reference shows that my own NDE may not be that far off.

The experiences of the cardiac arrest victims and fighter pilot trainees show that these phenomenon occur when the brain reaches a certain level of decreased oxygen and/or marked uptick in carbon dioxide. By contrast, NDEs are not experienced by persons barely clinging to life but whose brains have normal oxygen and carbon dioxide levels.

This suggests the features occur because of temporary changes to the brain, not nearness to death. Additionally, Dunning wrote, “Some brain surgeries, most notably those for epilepsy, produce very high rates of NDE reports from patients whose lives were not in danger.”

Researchers have found other ways to produce NDE symptoms on those not moribund. Dr. Karl Jansen managed this by giving ketamine to volunteers. Also, Nature reported that when researchers gave subjects electrical stimulation to a certain part of the brain, the volunteers felt they could see themselves from above.

Finally, this week the BBC wrote of another possible explanation for some NDE occurrences. Specifically, the effects of the powerful psychedelic drug DMT causes patients to feel surrounded by a brilliant glow and to glimpse past experiences.

None of this proves there’s no life after death. It simply strong evidence that these experiences result from understood, temporary changes to brain chemistry and not from someone crossing over then being snatched back.