25 DEC 2017
You might picture yourself walking through a field, or surrounded by loved ones. Or perhaps making your way down a long, dark tunnel, towards a brilliant, beckoning light.
When the end comes, what you experience will be a veiled secret known only to you – but whatever it is, scientists say those closing moments of consciousness could be powered by something amazing and mysterious taking place inside your brain.
In 2013, researchers at the University of Michigan found that after clinical death occurred in rats, their brain activity actually flared, revealing electrical signatures of consciousness that exceeded levels found in the animals’ waking state.
“We reasoned that if near-death experience stems from brain activity, neural correlates of consciousness should be identifiable in humans or animals even after the cessation of cerebral blood flow,” said one of the team, neurologist Jimo Borjigin.
And that’s exactly what they detected, with anaesthetised rats displaying a surge of highly synchronised brain activity within 30 seconds of an induced cardiac arrest, consistent with patterns you’d see in a highly aroused brain.
The phenomenon detected was a revelation, to the extent it may disprove the notion that just because blood flow has ceased as a result of clinical death, the brain must necessarily be rendered simultaneously inert.
“This study tells us that reduction of oxygen or both oxygen and glucose during cardiac arrest can stimulate brain activity that is characteristic of conscious processing,” said Borjigin.
“It also provides the first scientific framework for the near-death experiences reported by many cardiac arrest survivors.”
Of course, while the findings do establish a new framework for interpreting where near-death experiences might come from, it doesn’t necessarily follow that humans would undergo the same cognitive flare as rats journeying beyond the veil.
But if our brains somehow surge in the same way, it could help to explain the sense of awareness reported by many people who are successfully resuscitated in medical emergencies.
Somebody who knows a bit about that is critical care researcher Sam Parnia from Stony Brook University, who in 2014 released the world’s largest study examining near-death experiences and out-of-body experiences.
From interviews with more than 100 survivors of cardiac arrest, 46 percent retained memories of their brush with death, centred around a number of common themes, including bright lights, family, and fear.
But even more intriguingly, two of the patients were able to recall events related to their resuscitation that happened after they had died, which, according to conventional views about consciousness beyond clinical death, shouldn’t have been possible.
“We know the brain can’t function when the heart has stopped beating, but in this case conscious awareness appears to have continued for up to three minutes into the period when the heart wasn’t beating,” Parnia told The National Post, “even though the brain typically shuts down within 20 to 30 seconds after the heart has stopped.”
It sounds amazing, but it’s worth noting that the phenomenon was only reported by 2 percent of patients, and Parnia himself even later admitted “the easiest explanation is that this is probably an illusion“.
That ‘illusion’ could be borne out of a neurological response to physiological stress during cardiac events. In other words, a cognitive experience preceding – not following – the clinical death itself, and which is later remembered by the patient.
Certainly, that’s what many in the neuroscience community tend to think.
“Look, I’m sceptical,” neurologist Cameron Shaw from Deakin University in Australia told Vice earlier in the year.
“I think out-of-body experiences have been debunked, just because the mechanisms that produce sight and record memories are inoperative.”
According to Cameron, because the brain’s blood supply is pumped from underneath, the brain would die from the top downwards.
“Our sense of self, our sense of humour, our ability to think ahead – that stuff all goes within the first 10 to 20 seconds,” Julian Morgans reported for Vice.
“Then, as the wave of blood-starved brain cells spread out, our memories and language centres short out, until we’re left with just a core.”
Not a very encouraging outlook, but it’s worth noting that it also doesn’t accord with the experience of rats – and scientists are still finding evidence of surprising biological processes that continue to thrive even days after death stakes its claim.
All up, we’re out of answers, and while science has given us some fascinating insights into what the brain’s final moments might be, the research isn’t yet conclusive.
As we’ve said once before, when the curtain is drawn, we really have no firm idea of what it’s going to look or feel like. But we know for sure we’re all eventually going to find out.