13 Aug 2013
Near-death experiences exposed: Surge of brain activity after the heart stops may trigger paranormal visions
- U.S. scientists found something happens at the brink of death that pushes the conscious brain to a high level of arousal, potentially triggering visions
- The study is the first to take a systematic look at the neurophysiological state of the dying brain after a cardiac arrest
- As many as a fifth of people who survive cardiac arrests report having had an other-worldly experience while being 'clinically' dead
By Sarah Griffiths
Some believe they have caught a glimpse of the afterlife, others claim to have floated above their body, watching as medics save their lives.
But the reality of near-death experiences may be much more prosaic.
Research suggests that far from being a brush with the afterlife, they are caused by a rush of electrical activity in the dying brain.
In experiments on rats whose hearts had stopped, the pattern of activity was similar to that seen when the animals were fully conscious.
A mysterious surge of brain activity observed in dying rats may explain reports of near-death-experiences. Even after the animals' hearts stopped beating and no blood was reaching their brains, they appeared to show signs of conscious perception, said the scientists
However, the signals were up to eight times stronger. The researchers said that the discovery that the brain is highly active in the seconds after the heart stops suggests that the phenomenon has a physical, rather than spiritual nature.
It has been argued that the dying brain is incapable of such complex activity and so near-death experiences must have their origins in the soul.
It suggests something happens at the brink of death that pushes the conscious brain to a high level of arousal, potentially triggering the visions and sensations associated with near-death experiences (NDEs).
As many as a fifth of people who survive cardiac arrests report having had an other-worldly experience while being 'clinically' dead.
Typically NDEs involve travelling through a tunnel towards an intense light, being separated from the body, encountering long-departed loved ones or angels and undergoing some kind of judgment of 'life review.
Some emerge from NDEs as transformed individuals with a completely altered outlook on life, or a new belief in religion.
But many scientists believe near-death-experiences are nothing more than hallucinations induced by the effect of the brain shutting down.
As many as a fifth of people who survive cardiac arrests report having had an other-worldly experience while being 'clinically' dead. Dr Jimo Borjigin, from the University of Michigan, said the study tells us reduction of oxygen during cardiac arrest can stimulate brain activity that is characteristic of conscious processing
The new research involved recording the electrical nerve impulses of anaesthetised rats whose hearts were artificially stopped.
Within 30 seconds after suffering a cardiac arrest, all the animals displayed a short-lived surge of widespread, highly synchronised brain activity.
'We were surprised by the high levels of activity,' said Dr George Mashour, one of the US researchers from the University of Michigan in Ann Arbor.
'In fact, at near-death many known electrical signatures of consciousness exceeded levels found in the waking state, suggesting that the brain is capable of well-organised electrical activity during the early stage of clinical death.'
Near death experiences involve travelling through a tunnel towards an intense light, being separated from the body, encountering long-departed loved ones or angels
The findings are reported in the journal Proceedings of the National Academy of Sciences.
Previously it was assumed that brain activity ceases when the heart stops.
Lead scientist Dr Jimo Borjigin, also from the University of Michigan, said: '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.'
'It also provides the first scientific framework for the near-death experiences reported by many cardiac arrest survivors.'
However, other scientists have been cautious that the study might shed light on the human condition at the moment of death.
Dr Chris Chambers, Senior Research Fellow at Cardiff University, admitted it is tempting to draw a link between a surge of neural activity and consciousness but there are two barriers to doing so.
'The first is that we don't know to what extent rats experience consciousness at all, so we don't know what the activity means.
'Second, even if rats are conscious, to conclude from their brain activity alone that these bursts of activity reflect consciousness would be a logical fallacy known as reverse inference.
'To overcome these limitations we would need to run a study in humans and relate the changes in activity to what they report about their conscious experience.'