Generally, doctors consider the surest indication that someone has died when the person goes into cardiac arrest, the cessation of the electrical shock that drives the heartbeat. As a consequence, the heart stops.
What happens in our mind during this process?
Scientists have studied near-death experiences (NDEs) to try to understand how death overtakes the brain. What they have discovered is surprising: a surge of electricity enters the brain moments before brain death. A 2013 study, which examined electrical signals inside the heads of mice, found that the rodents went into a hyper-alert state just before death.
Some scientists are beginning to think that NDEs are caused by reduced blood flow, coupled with abnormal electrical behavior within the brain. Thus, the stereotyped tunnel of white light could derive from an increase in neuronal activity.
Dr. Sam Parnia is director of critical care and resuscitation research at NYU Langone School of Medicine in New York. He and his colleagues have investigated exactly how the brain dies.
The medical staff confirms it.
But how is it possible for technically dead people to be aware of what is happening around them? According to Dr. Parnia, even when our breathing stops and our heart stops beating, we remain conscious for between 2 and 20 seconds. That is how long the cerebral cortex is thought to last without oxygen. It is the part of the brain responsible for thinking and making decisions. It is also responsible for deciphering the information our senses collect.
According to Dr. Parnia, during this period, “all the reflexes in the brainstem are lost: for example, the pupillary reflex, all of that disappears.” Brain waves from the cerebral cortex soon become undetectable. Even so, our thinking organ can take hours to completely shut down.
Normally, when the heart stops beating, someone performs CPR (cardiopulmonary resuscitation). This will provide approximately 15% of the oxygen needed for normal brain function. “If you can restart the heart, which is what CPR tries to do, little by little you will start to get the brain working again,” says Dr. Parnia.
Other research by Dr. Parnia and his colleagues examined the large number of Europeans and Americans who have suffered cardiac arrest and survived. “We are trying to understand the exact characteristics that people experience when they go through death, because we understand that this is going to reflect the universal experience that we are all going to have when we die.”
One of the objectives is to observe how the brain acts and reacts during cardiac arrest, both in the death process and in the resuscitation process. How much oxygen is needed exactly to revive the brain? How is the brain affected after resuscitation? More knowledge about it could improve resuscitation techniques, which could save countless lives each year.
“At the same time, we also study the human mind and consciousness in the context of death,” said Dr. Parnia, “to understand whether consciousness annihilates or continues after death for some period of time – and how that relates to what is happening inside the brain in real time.”
Keep reading:
* She was clinically dead for 3 minutes and revealed her experience in the “afterlife”
* “It was endless”: She was clinically dead for 7 minutes and this was her experience
* “I did not see the light at the end of the tunnel”: Británico narrates his experience after being declared dead