The reassuring idea of 'the light at the end of the tunnel' which supposedly greets us in our dying moments might not always ring true. The truth can be far more clinical, stark and deeply unsettling.

Similar to being plunged into freezing water, as death approaches, our brains begin shutting down certain regions, prioritising only the most critical functions needed to sustain our vital organs.

This disconnect between brain activity and bodily function may account for the diverse accounts people share following near-death experiences. Yet there's scientific backing for one of the most disturbing peculiarities surrounding these experiences.

• NHS GP warning to anyone taking omeprazole for acid reflux - and one 'red flag'


• 21.5 stone woman loses 10 stone in 6 months eating same meal every day

Some people have reported hearing medical staff announce their own time of death - and research supports this phenomenon.

The brain can occasionally continue functioning after someone has died, remaining active long enough to register their time of death being called out.

Dr Sam Parnia, director of critical care and resuscitation research at NYU Langone School of Medicine in New York City, gathered a team to examine a group of people who temporarily died after cardiac arrest before being brought back to life.

A pioneering study has discovered some patients claim to have been conscious and heard conversations after being declared dead by doctors.

The largest research of its kind has unearthed accounts from people who reported having awareness and observing events around them, even after being pronounced dead.

According to Dr Sam Parnia, death is defined as the moment when the heart stops beating and blood flow to the brain is cut off. He explained: "Technically, that's how you get the time of death – it's all based on the moment when the heart stops."

Consequently, brain function abruptly ends, and all brain stem reflexes, including the gag reflex and pupil reflex, vanish.

However, studies suggest that the brain may emit a brief burst of energy just before death. A 2013 study at the University of Michigan found that the brains of anaesthetised rats undergoing induced heart attacks showed activity patterns associated with a "hyper-alerted state" in the short period following clinical death.

Dr Parnia said: "In the same way that a group of researchers might be studying the qualitative nature of the human experience of 'love', for instance, we're trying to understand the exact features that people experience when they go through death, because we understand that this is going to reflect the universal experience we're all going to have when we die."