August 12, 2013
A sense of peace, tranquility, perhaps even euphoria. A powerful feeling of being disconnected from one’s own body. A sensation of floating upward, through a tunnel, perhaps towards a bright light.
Over the past few decades, as our ability to resuscitate patients suffering from cardiac arrest has improved, thousands of people worldwide have reported these experiences in the moments just after their heart stopped pumping blood—a condition formally known as clinical death—and before they were fully resuscitated. Many take these near-death experiences to be evidence of the afterlife, a tantalizing window into the journey that our souls might undergo after our time on Earth is over.
Proving the existence of the afterlife is, of course, beyond the scope of science. But something physical might be able to explain the phenomena of near death experiences, according to a new finding by a team of neuroscientists from the University of Michigan. They observed, at least in the brains of rats, a sudden surge of electrical activity that continues for roughly 30 seconds after clinical death. This activity, they write in a study published today in the Proceedings of the National Academy of Sciences, “demonstrate[s] that the mammalian brain can, albeit paradoxically, generate neural correlates of heightened conscious processing at near-death.”
In other words, if human brains work the same way as rats’ do, our near-death experiences are most likely a random jolt of activity in our brain just before it shuts down permanently.
The field of near-death studies is a controversial one. It’s largely populated by researchers looking into the psychology of the phenomenon, who conduct interviews with people who’ve gone through near-death experiences about what they remember. Some argue that their interpretations of the data are often biased by preexisting religious leanings.
The Michigan team, led by neurologist Jimo Borjigin, took a very different approach to examining these episodes. They sought to use electroencephalography (EEG, a technique that measures electrical activity among different areas of the brain) to track what exactly goes on in the seconds after the heart stops pumping blood, or the lungs stop taking in oxygen.
Of course, they couldn’t do this with human subjects, so they subjected lab rats to what seems to be a pretty gruesome experience in the name of science: They anesthetized nine rats and forcibly induced cardiac arrest, causing the rodents’ hearts to stop pumping blood, while they monitored brain activity with an EEG.
They found that, in all nine rats, brain activity continued for roughly 30 seconds after the animals’ blood stopped pumping. The activity persisted in all six regions of the brain they monitored, and gradually declined over the course of the 30 seconds before disappearing.
Although the team had predicted they’d find some activity, “we were surprised by the high levels,” George Mashour, a co-author, said in a press statement. “At near-death, many known electrical signatures of consciousness exceeded levels found in the waking state, suggesting that the brain is capable of well-organized electrical activity during the early stage of clinical death.”
To see whether this activity was caused by something specific about cardiac arrest in particular—say, the experience of pain—they also suffocated other rats while measuring their brain activity. They found virtually the same patterns of data, indicating that the activity is inevitably generated by the brain in the final moments before it shuts down.
In both cases, many characteristics of the brain activity correlated with the activity they’d measured earlier in the rats when they were fully conscious. The clear implication is that these rats may have been going through their own near-death experiences in the lab, just before dying.
If these same patterns of brain activity occur in humans just after cardiac arrest—something that will be difficult to determine, given the problems of hooking up people to EEGs while they’re being resuscitated—it could go a long way toward explaining why humans have out-of-body experiences when they near death without the need to invoke souls or the afterlife. Just as the activity in our brains during the REM stages of sleep accounts for the experience of dreaming, this data could account for the sensation of continuing awareness after clinical death.
Other researchers have previously speculated about physiological explanations for the other typical descriptions of near-death experiences. It’s been documented that when people faint, for example, the loss of blood flow to the brain can generate a narrowing of the field of vision—perhaps explaining the tunnel often described in their memories. The release of epinephrine and other chemicals in the brain during moments of stress, meanwhile, could account for the sense of euphoria.
There’s still a ton of research to be done before we have any comprehensive understanding of what’s going on in the brain during its final moments—something that can also be said, really, for the current state of knowledge regarding all aspects of how the brain works. But this finding firmly reinforces basic tenets of the scientific method: Although discussion of the afterlife and the supernatural have a place in philosophical and theological realms, it need not be used to explain near-death experiences—physical processes can do that just fine.
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