Scientists have wondered if the commonalities of these experiences point to a fundamental biological process that underlies them.
The new study, published Monday in the journal PNAS, provides the first evidence of an increase in brain activity correlated with consciousness in dying comatose patients.
“How a living experience can emerge from a dysfunctional brain during the dying process is a neuroscientific paradox”said in a statement the co-author of the study, George Mashour from the University of Michigan in the USA.
It was determined that the patients could no longer be helped medically and, with the permission of their families, they were disconnected from life support.
When ventilator support was removed, two of the patients showed an increase in heart rate, along with an increase in “gamma” brain wave activity, considered the fastest brain activity and associated with consciousness.
The researchers also detected activity in the so-called “hot zone” of the neural correlates of consciousness, the junction between the temporal, parietal and occipital lobes, present in the back of the brain.
Previous studies have found that this area of the brain is linked to dreaming, visual hallucinations in epilepsy and altered states of consciousness in other brain studies.
While the two patients had previous reports of seizures, none were observed during the hour before their deaths.
According to the scientists, the other two patients did not show the same increase in heart rate when they were disconnected from life support, nor did they have increased brain activity.
Because the study’s sample size was very small, the researchers caution against making conclusive remarks about the implications of the research, but added that the findings are “certainly interesting” and provide a new framework for understanding consciousness in dying people.
Also, it is impossible to know exactly what the patients experienced, because they did not survive.
The latest research follows a landmark study last year that involved the brain activity of a dying person and revealed patterns around the time of death similar to those seen during dreams and recollection.
In this study, scientists were analyzing the brain waves of an 87-year-old patient with epilepsy to detect seizures using an EEG device, but the patient suffered a heart attack and died in the middle of the research.
An analysis of the EEG recordings showed that while the person was dying, there was an increase in gamma brain wave activity, leading scientists to speculate that the dying 87-year-old may have made a ” last reminder of life”.
“Given that cross-coupling between alpha and gamma activity is involved in cognitive processes and memory recall in healthy subjects, it is intriguing to speculate that such activity might underpin a last ‘recall of life’ that might occur in state of near death“, the researchers wrote in the previous study.
The latest findings also highlight the need to reassess the role of the brain during cardiac arrest, the scientists said.
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