Philosophers have grappled with the question of how the mind is related to the brain
for millennia. It’s hard to equate the richness of our mental lives with the lump of warm meat in our heads, but the view of mainstream neuroscience is that the mind is an emergent property of the brain. Without the brain, there is no mind, and every mental experience has an underlying neurophysiological correlate.
This view is challenged by dramatic accounts of near-death experiences (NDEs), in which a person’s mind—their consciousness—appears to continue functioning, even whilst their brain is incapacitated. Stories of heart-attack patients and other trauma victims floating above their bodies, seeing tunnels with a welcoming light at the end, reliving their autobiographies, and even meeting deceased relatives, have existed since at least the nineteenth century.
Recently, near-death phenomena have attracted fresh attention with the publication by a neurosurgeon of his own sensational first-hand account of a near-death experience: Proof of Heaven, A Neurosurgeon’s Journey Into The Afterlife (Simon & Schuster, 2012).
Dr. Eben Alexander describes in Newsweek how in 2008 he was left comatose by a brain infection, his cortex “stunned to complete inactivity." During that time he says he travelled to a place with “big, puffy, pink-white” clouds, “flocks of transparent, shimmering beings” and that he rode on a butterfly wing with a beautiful woman with golden tresses, “high cheekbones and deep-blue eyes." Freely admitting his identity as a “faithful Christian” prior to the trauma, Dr. Alexander believes his experience proves the existence of the afterlife and that consciousness is not rooted to the brain.
Sceptics have been quick to pour scorn on the doctor’s interpretation. Writing for The Telegraph, the eminent neuroscientist Colin Blakemore thought it revealing that Alexander’s near-death account, like so many others, was saccharine, reassuring and full of biblical metaphor. On his blog, Sam Harris, the arch-atheist, expressed his bewilderment (as did Blakemore) at the neurosurgeon’s apparent ignorance of basic brain science. “Everything—absolutely everything—in Alexander’s account rests on repeated assertions that his visions of heaven occurred while his cerebral cortex was ‘shut down,’ ‘inactivated,’ ‘completely shut down,’ ‘totally offline,’ and ‘stunned to complete inactivity’,” Harris wrote. “The evidence he provides for this claim [including a structural CT scan] is not only inadequate—it suggests that he doesn’t know anything about the relevant brain science.”
Do NDE’s really prove the mind can survive without a brain?
Around 12 to 18 percent of people who survive cardiac arrest report having had a near-death experience. Just like the butterfly-riding neurosurgeon, some researchers in the field think a purely materialist view of the mind is challenged by all these experiences of complex mental states occurring during periods of brain inactivity.
One such expert is Bruce Greyson at the University of Virginia. In his 2010 paper, Implications of Near-Death Experiences for a Postmaterialist Psychology, Greyson also draws attention to accounts from Near-Death experiencers that they could see and hear things in the real world during their spell of brain incapacitation—for example, witnessing surgeons operating on them. Greyson argues that the “conflict between a materialist model of brain–mind identity and the occurrence of NDEs under conditions of general anesthesia or cardiac arrest is profound and inescapable.”
There’s no doubt the reports of NDEs are fascinating. If nothing else, these people have clearly lived through an unusual, emotionally intense psychological event. But should we abandon the idea that the mind is rooted in the brain, given that to do so would shake our understanding of the natural laws of science to its very foundations?
As things stand, there are good reasons to doubt that NDEs disprove the inextricable mind-brain connection. First off, many of the features of NDEs occur in other situations when we have no reason to believe anything particularly brain-defying is going on. For instance, out-of-body experiences are frequently reported during sleep paralysis (a relatively common occurrence in which wakefulness intrudes on REM dream-sleep), and they’ve been triggered by direct stimulation of the right tempero-parietal junction (during surgery for intractable epilepsy). Pilots exposed to high G-force often report a tunnelling of their vision, caused by a lack of blood and oxygen supply to the eyes. The effects of hypoxia and many recreational drugs—for example the trips experienced by ketamine users—also resemble aspects of the NDE, including the hallucinations. These examples, and there are many others, demonstrate that it’s perfectly possible for changes in the brain to lead to unusual experiences akin to elements of the NDE.
Perhaps the biggest problem with taking accounts of NDE too literally, is that they are by necessity always retrospective, rendering them prone to memory tricks and biases. Greyson and others, who think that NDEs challenge a materialist account of the mind, always emphasise how the NDE occurs during brain inactivity—that NDEs are therefore a case of the mind-brain link being broken. But we can’t know that that’s really true. Often the precise amount of brain activity that’s still ongoing is unknown. And it’s possible the NDE itself occurred in the lead up to brain inactivity, or during the post-trauma recovery.
Perhaps most dramatic would be evidence of NDE patients having access to information that could only have been available if they really were floating atop the room, “fully alert” whilst in surgery. But existing accounts of these claims are purely anecdotal, and it’s possible patients heard what was going on whilst under anaesthesia, or pieced together snippets of information they heard before or after the surgery.
During a study published in 2001 (pdf), involving 63 cardiac arrest survivors, researchers hung boards close to the ceiling, with pictures on them that could only be seen from above. The idea was to test whether patients reporting an out-of-body experience would be able to recall the pictures, but unfortunately, none of the Near-Death experiencers in this study had an out-of-body experience. Greyson also claims that some patients have encountered dead people during a NDE, of whose death they had no prior knowledge. However, these claims too are largely anecdotal.
Taken all together, it’s clear there’s much we have to learn about the underlying biological processes that give rise to NDEs. It’s also important that we do more research into the longer-term psychological effects on patients who live through one of these episodes. Inevitably, many people will continue to cling onto NDEs as evidence for the human soul—for the possibility that the self can cast off its neural ties. But as the psychologists Dean Mobbs and Caroline Watt concluded in a review published in 2011 for the respected journal Trends in Cognitive Sciences, there is at present no reason to believe that NDEs are paranormal. “Instead,” they wrote, “near-death experiences are the manifestation of normal brain function gone awry.” Meanwhile research on NDEs is on-going. Earlier this year the Templeton Foundation earmarked $5 million for its multi-disciplinary Immortality Project, part of which will involve cross-cultural research into near-death phenomena.