The largest scientific study of its kind reveals evidence that consciousness continues for at least several minutes after clinical death.
via Bioethics Research Library:
The results revealed that 40% of those who survived a cardiac arrest were aware during the time that they were clinically dead and before their hearts were restarted. Dr. Parnia, in the interview stated: “The evidence thus far suggests that in the first few minutes after death, consciousness is not annihilated. Whether it fades away afterwards, we do not know, but right after death, consciousness is not lost. 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, even though the brain typically shuts down within 20-30 seconds after the heart has stopped. 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. Furthermore, the detailed recollections of visual awareness in this case were consistent with verified events”.
The study director continued, saying that, “A total of 2060 cardiac arrest patients were studied. Of that number, 330 survived and 140 said that they had been partly aware at the time of resuscitating”. Of these latter, states Parnia, “thirty-nine per cent […] described a perception of awareness, but did not have any explicit memory of events”, which suggests, according to Dr. Parnia, that “more people may have mental activity initially but then lose their memories, either due to the effects of brain injury or sedative drugs on memory recall”.
He continued, saying: ” One in five said they had felt an unusual sense of peacefulness while nearly one third said time had slowed down or speeded up. Some recalled seeing a bright light; a golden flash or the Sun shining. Others recounted feelings of fear or drowning or being dragged through deep water. 13 per cent said they had felt separated from their bodies and the same number said their sensed had been heightened.”
Parnia believes that, “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.”