Is brain hyperactivity to blame?
People who literally jumped off the shovel at the last second often report amazing near-death experiences. One reason for this could be an overactive brain at the moment of death. At least that is what the study by a US research team suggests, the results of which were published in the journal “Proceedings” of the US National Academy of Sciences (PNAS).
A white light at the end of the tunnel, your own dying body from above, or life in fast forward: Such experiences are repeatedly reported by people who have survived a cardiac arrest, for example. However, the scientific explanation for such near-death experiences is still being discussed. Now, a study led by University of Michigan brain researcher Jimo Borjigin provides evidence of a surge in activity that correlates with awareness in the dying brain.
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Already ten years ago, Borjigin’s research team had shown with experiments on rats that in the first 30 seconds after a cardiac arrest in the animals, conspicuously synchronous patterns of very specific brain waves could be measured. From that study, the scientists concluded that the brain is capable of well-organized electrical activity in the early stages of clinical death.
Gamma waves show striking patterns in the dying
In the new work, the team reports similar signatures in the brains of dying people who have suffered cardiac arrest. Specifically, the researchers recorded the brain activity of four comatose, dying patients using electroencephalography (EEG).
An EEG visualizes the brainwaves that occur when neurons communicate with each other via electrical impulses. Different brainwaves oscillate in different frequency ranges depending on the state of consciousness: the delta waves, which are particularly strong during deep sleep, oscillate at a frequency of one to three hertz per minute, for example, while this frequency is between 25 and 140 hertz for the very fast gamma waves.
Those same gamma waves showed striking patterns in at least two of the patients: in them, stopping the ventilators triggered a transient and widespread increase in gamma wave activity and an increase in heart rate. Gamma oscillations are associated with increased alertness and concentration, information processing, and memory retrieval in the healthy brain. In addition, they can be measured during dreaming and deep meditation.
Brain can be active during cardiac arrest
A paper published last year in the journal Frontiers in Aging Neuroscience reported similar brain wave patterns in a single patient whose brain activity was recorded 15 minutes around the time of death. This patient had suddenly presented with epileptic seizures after an operation on the head.
The two patients described in the current study with the increased gamma wave activity had previously had seizures, but not in the hour before their death. They were also found to have activity in an area of the brain previously associated with dreams, visual hallucinations in epilepsy, and altered states of consciousness.
Overall, the authors conclude, their study suggests that the human brain can be active during cardiac arrest and lays the groundwork for further research into human consciousness. In view of the small number of samples, however, they warn against making sweeping statements about the meaning of the results. In addition, it is impossible to know what the patients experienced since they died.
The research paper states: “We cannot rule out that the increase in gamma values is a sign of a pathological process that only occurs in the dying phase and has nothing to do with conscious processing.”
Is there a hidden consciousness in the dying?
In fact, the lack of oxygen that occurs after death leads to a whole series of changes in the brain that make it difficult to clearly recognize signs of consciousness: If the blood circulation stops, the brain stops communicating between the nerve cells, certain rhythms in the brain’s electrical system shift, the cells once again have an electrical output.
As early as 2018, German and US neurologists described in the journal “Annals of Neurology” that this happens in the form of a spreading discharge wave. Nonetheless, the results now published are exciting and provide a new framework for our understanding of hidden consciousness in the dying human, says co-author and neurologist Nusha Mihaylova.
“How vivid experiences can emerge from a dysfunctional brain during the dying process is a neuroscientific paradox,” adds co-author George Mashour, founding director of the Michigan Center for Consciousness Science. The study helps to elucidate the underlying neurophysiological mechanisms.
However, larger, multi-centre studies of EEG-monitored ICU patients who have survived cardiac arrest would be helpful: they could provide much-needed data to determine whether the bursts of gamma activity are evidence of latent consciousness in the immediate vicinity of death .
RND/dpa
