by Researchers at the Paris Brain Institute have made a groundbreaking discovery regarding the brain dynamics during the phenomenon known as the “wave of death.” This wave, which is observed when brain oxygenation is cut off for an extended period, causes the electrical activity of the cerebral cortex to rapidly diminish. However, it has now been found that the wave of death originates deep within the cortex and gradually spreads until consciousness is extinguished. Importantly, this wave does not necessarily indicate permanent death, as a wave of resuscitation can follow if the brain is successfully reoxygenated.
Published in the journal Neurobiology of Disease, the research provides crucial insights into identifying the populations of neurons most susceptible to damage during cardiorespiratory arrest. Understanding this vulnerability could help reduce the risk of neurological complications. The concept of death is complex, and from a neurological perspective, it is not defined by a specific moment but rather a process that can last several minutes and potentially be reversible in some cases.
In a previous study conducted by the Dynamics of Epileptic Networks and Neuronal Excitability team at the Paris Brain Institute, it was revealed that when the brain experiences oxygen deprivation, known as anoxia, a cascade of changes occurs in brain activity. The depletion of ATP, the cells’ fuel source, disrupts the electrical balance of neurons and triggers a release of glutamate, an essential excitatory neurotransmitter.
The initial phase following oxygen deprivation involves a shutdown of neural circuits, followed by a surge in brain activity marked by increased gamma and beta waves. These waves are typically associated with conscious experiences and could potentially be linked to near-death experiences reported by individuals who have survived cardiorespiratory arrest. As neuronal activity gradually diminishes, the brain reaches a state of electrical silence, characterized by a flat electroencephalogram. However, this silence is swiftly interrupted by a depolarization of neurons known as the wave of death. This wave causes structural and functional alterations in the brain and serves as a definitive marker of the cessation of all brain activity.
The recent study sought to determine the origin and propagation of the wave of death within the cortex. By measuring local field potentials and recording the electrical activity of individual neurons in the primary somatosensory cortex of rats, the researchers made significant observations. They found that the wave of death originates in pyramidal neurons located in layer 5 of the neocortex and spreads upward towards the brain’s surface and downward towards the white matter. This pattern was consistent across different experimental conditions and suggests that the deeper layers of the cortex are particularly vulnerable to oxygen deprivation due to the high energy needs of the pyramidal neurons in layer 5.
Moreover, the researchers demonstrated that reoxygenating the brains of the rats enabled the replenishment of ATP reserves in the cells, resulting in the repolarization of neurons and the restoration of synaptic activity. This finding highlights the potential for restoring brain functions even after a flat electroencephalogram has been observed.
These findings improve our understanding of the neural mechanisms underlying changes in brain activity as death approaches. It emphasizes that death is a gradual process that cannot be strictly separated from life based on physiological observations. Additionally, a flat electroencephalogram does not necessarily signify the definitive cessation of brain functions.
Moving forward, the researchers aim to establish the conditions under which brain functions can be restored and develop neuroprotective drugs to support resuscitation during cardiac and respiratory failure. This research opens up new avenues for potentially saving lives and minimizing the neurological consequences of oxygen
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1. Source: Coherent Market Insights, Public sources, Desk research
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