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.
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."
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."
- DAILY MAIL
