After death, are you aware that you’ve died?

The moment the heart stops is considered time of death. But does death overtake our mind immediately afterward or does it slowly creep in?

Scientists have studied near death experiences to try to gain insights into how death overcomes the brain. What they’ve found is remarkable, a surge of electricity enters the brain moments before brain death. 

Scientists are beginning to think a near death experiences is caused by reduced blood flow, coupled with abnormal electrical behavior inside the brain. So, the stereotypical tunnel of white light might derive from a surge in neural activity.

Those who have had such experiences talk about floating around the room and being aware of the medical team working on their body.

So how could those who were technically dead be cognizant of what’s happening around them? Even after our breathing and heartbeat stops, we’re conscious for about 2-20 seconds, Dr. Parnia says. That’s how long the cerebral cortex is thought to last without oxygen. This is the thinking and decision-making part of the brain. It’s also responsible for deciphering the information gathered from our senses.

According to Parnia during this period, "You lose all your brain stem reflexes — your gag reflex, your pupil reflex, all that is gone." Brain waves from the cerebral cortex soon become undetectable. Even so, it can take hours for our thinking organ to fully shut down.

Usually, when the heart stops beating, someone performs CPR (cardiopulmonary resuscitation). This will provide about 15% of the oxygen needed to perform normal brain function. "If you manage to restart the heart, which is what CPR attempts to do, you'll gradually start to get the brain functioning again,” Parnia said. “The longer you're doing CPR, those brain cell death pathways are still happening — they're just happening at a slightly slower rate."

One of the objectives is to observe how the brain acts and reacts during cardiac arrest, through the process of death, and during revival. How much oxygen exactly does it take to reboot the brain? How is the brain affected after revival? Learning where the lines are drawn might improve resuscitation techniques, which could save countless lives per year.