It is possible for consciousness to persist even after the body dies, confirm British scientists, who examined 2,060 patients from the UK, America and Austria. About 40 per cent of the patients said that they could remember some kind of awareness, though they had been declared "dead" for a while.

It is not true that the brain ceases its activity 30 seconds after the heart stops beating. Awareness does not cease at the same time, say the scientists. 

According to Dr Sam Parnia, Assistant Professor of Critical Care Medicine and Director of Resuscitation Research at The State University of New York at Stony Brook, USA, as well as the study's lead author, people may be undergoing mental activity at first after returning to life, but after a while they lose their recall of the time they had been "dead", most probably due to the effects of sedative drugs or brain injury on the memory.

"Contrary to perception, death is not a specific moment but a potentially reversible process that occurs after any severe illness or accident causes the heart, lungs and brain to cease functioning. If attempts are made to reverse this process, it is referred to as 'cardiac arrest'; however, if these attempts do not succeed it is called 'death,'" Parnia had said in a 2014 statement.

About two percent of the patients seemed to recollect an outer body experience, in which they seemed to be completely aware of their environments. However, half of them underwent fear, not awareness.

One 57-year-old could remember what happened around him after he suffered a cardiac arrest and seemed to be dying. Whatever he experienced was explained with "such eerie accuracy" that he is believed to be the first confirmed patient who experienced an out-of-body experience.

"This is significant, since it has often been assumed that experiences in relation to death are likely hallucinations or illusions occurring either before the heart stops or after the heart has been successfully restarted, but not an experience corresponding with 'real' events when the heart isn't beating," Parnia explained.

"In this case, consciousness and awareness appeared to occur during a three-minute period when there was no heartbeat. This is paradoxical, since the brain typically ceases functioning within 20-30 seconds of the heart stopping and doesn't resume again until the heart has been restarted. Furthermore, the detailed recollections of visual awareness in this case were consistent with verified events."

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