How the human brain dies: scientists have made an intriguing discovery

Death is still a huge mystery for science. And its study remains a priority, in part because it will allow us to better understand how to delay it in time. And now scientists have made a rather significant discovery related to the death of the human brain.

A team of researchers from the Paris Brain Institute at the Sorbonne was finally able to determine the sequence of events leading to the final cessation of neural activity. These results not only shed light on the strange phenomena reported by people who have had near-death experiences but may also lead to the development of new medical techniques designed to reverse the process of brain death, IFL Science writes.

The process of brain death has remained a mystery to scientists because, unlike the body, it does not die at a certain point but stops working gradually. Most likely, when the body's oxygen reserves are depleted, neurons quickly deplete their reserves of cellular fuel, known as ATP (adenosine triphosphate), and lose stability.

This causes a massive release of the neurotransmitter glutamate, which excites the nervous system. And it causes a surge of nervous activity after a person dies. "At first, it seems that the nerve circuits are disconnected... Then we see a surge in brain activity, in particular, an increase in gamma and beta waves," Severine Mahon, one of the study's authors, explained in a statement.

"Usually, such waves are associated with conscious experience. But in this context, they can be involved in so-called near-death experiences. They are reported by people who at some point found themselves on the verge of life and death, having experienced cardiopulmonary arrest.

Gradually, such activity of the nervous system fades to electric silence, but even this moment is not considered the end of life. This silence is suddenly interrupted by a high-amplitude wave that spreads through the brain, causing irreversible functional and structural changes in it. Scientists call it a "death wave". This phenomenon is caused by the depolarization of neurons in the last moments of their life. "This critical event, called anoxic depolarization (AD), causes neuronal death throughout the cortex," Antoine Carton-Leclercq, another author of the study, explained. He compared this event to a swan song and described it as a true marker of the transition to the cessation of all brain activity.

Researchers claim that this process can be reversed if the brain is saturated with oxygen (reoxygenated) before the "death wave" finally completes its work. But until now, scientists did not know where exactly in the brain this impulse occurs and how it spreads.

To get closer to the answer, scientists from the Paris Brain Institute studied electrical activity in the brains of rats that had suffered from Alzheimer's disease. They found that the death wave begins with the excitation of neurons in the deeper layers of the cerebral cortex. This is probably because this group of nerve cells has a particularly high energy demand. According to scientists, the onset of Alzheimer's disease was not the same in all cortical layers. Initially, it occurred in layers 5 and 6, and then spread bi-directionally, up and down, they explained in their study.

However, when the researchers reoxygenated the brains of the rats, the process was reversed. This helped restore ATP stores and polarize neurons. "We observed the same dynamics in different experimental conditions and believe that it may exist in humans," Mahon explained the team's findings.

Having identified all the stages of brain death, the authors of the study proved that the dying process is not necessarily irreversible. Certain actions can potentially bring a person back to life even after the indicators of brain activity have disappeared. More importantly, the study, published in the journal Neurobiology of Disease, provides new insight into how to protect the brains of patients who have suffered cardiorespiratory failure from damage.

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