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Time of death is considered when a person has gone into cardiac arrest, which is the cessation of the electrical impulse that drives the heartbeat. As a result, the heart locks up. At that time when when the heart stops is considered by medical professionals to be proved that someone has died.
But what is going inside our mind during this process? Does death immediately overtake our subjective experience or does it slowly creep in?
Scientists have studied near-death experiences (NDEs) to gain the awareness into how death overcomes the brain. What they’ve found is remarkable: A surge of electricity enters the brain moments before brain death. One 2013 study, which examined electrical signals inside the heads of rats, found that the rodents entered a hyper-alert state just before death.
Some scientists think that NDEs are 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. Dr. Sam Parnia is the director of critical care and resuscitation research, at NYU Langone School of Medicine, in New York City. He and his companions have detected exactly how the brain dies.
In previous work, Dr. Parnia has conducted animal studies looking at the moments before and after death. He’s also detected near-death experiences. “Many times, those who have had such experiences talk about floating around the room and being aware of the medical team working on their body,” Dr. Parnia told us. “They’ll explain watching doctors and nurses working and they’ll explain having awareness of full conversations, of visual things that were going on, that would otherwise not be known to them.”
Medical staff confirm this, he said. But how could people who were technically dead be aware of what’s happening around them? Even after our breathing and heartbeat stop, we remain conscious for about two to 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.
