A recent study published in Proceedings of the National Academy of Sciences have presented preliminary results suggesting that there may be an increase in brain activity associated with consciousness during the dying process.
The new study aimed to examine the brain activity of patients during the dying process, particularly focusing on whether there are any neural correlates of consciousness. Near-death experiences (NDEs) have been reported by some cardiac arrest survivors and are described as very vivid and life-like experiences. These experiences challenge our understanding of brain function during cardiac arrest, when consciousness is thought to be absent.
Previous research has shown that high-frequency brain oscillations, specifically gamma activities, are associated with consciousness. In animal experiments, sudden cessation of cardiac function or acute asphyxia has been shown to stimulate gamma activities. However, no studies have examined the neural correlates of dying humans that could explain the subjective experiences reported in NDEs.
“My lab has been studying the dying brain since 2013 and was the first to detect the increase in gamma oscillations in the dying process in rats (Borjigin et al., 2013; Li et al., 2015), when I was shocked to realize , that science/medicine knows little about the brain during the death process,” said study author Jimo Borjigin, an associate professor in the Department of Molecular and Integrative Physiology with a joint appointment in Neurology at the University of Michigan Medical School.
Gamma oscillations are rhythmic patterns of neural activity that occur in the gamma frequency range, typically from 25 to 100 Hz (cycles per second). They are a type of high-frequency brain wave activity observed in the electroencephalogram (EEG), which measures the electrical activity of the brain.
Gamma oscillations are thought to play a crucial role in various cognitive processes, including perception, attention, memory and consciousness. They are thought to coordinate and synchronize neural activity across different brain regions, enabling efficient communication and information processing.
“A better understanding of the brain’s role during cardiac arrest can help save dying patients. It will also help with a better understanding of the NDE phenomenon,” Borjigin told PsyPost.
The researchers identified four patients who died of cardiac arrest while under EEG monitoring. These patients were comatose and unresponsive and determined to be without medical assistance. With the families’ permission, ventilator support was withdrawn.
Two of the patients showed an increase in heart rate and an increase in gamma wave activity when life support was removed. This activity was observed in the brain’s “hot zone” associated with consciousness, specifically the junction between the temporal, parietal and occipital lobes.
The research raises the possibility that patients who experience cardiac arrest and are therefore considered clinically dead may still have some level of consciousness that is not externally visible or detectable.
“The high levels of organized brain activity remaining in the apparently comatose patients suggest that there is much to learn about the brains of comatose patients, as they may not be beyond the help of future drugs,” Borjigin told PsyPost.
The results indicate that withdrawal of ventilatory support can stimulate a transient and widespread increase in gamma activities in certain patients who are close to death. These gamma activities include various functions such as increased gamma power, coupling of gamma oscillations with slower oscillations, functional and directed connectivity in the brain, and communication between different brain regions.
According to Borjigin, the study provides evidence that “the human brain can be activated by the process of death.”
“The activated brain shows neural signatures of consciousness. Therefore, the NDE is most likely the product of the activated brain.”
But the researchers noted that their study had a small sample size, and they cautioned against making broad conclusions based on the findings. As the patients did not survive, it is also impossible to know what subjective experiences they may have had.
“We found the gamma increase in 2/4 patients. Data from more dying patients need to be analyzed to see how common this increase is among those dying in coma,” said Borjigin.
The researchers said larger multicenter studies involving ICU patients with EEG monitoring who survive cardiac arrest could provide further insight and data to determine whether these bursts of gamma activity indicate hidden consciousness even near death. Studying the process of death, specifically cardiac arrest, could provide valuable insight into the mechanisms underlying human consciousness, they added.
“I am very optimistic that the neural basis of the NDE will be fully elucidated in the near future,” Borjigin said.
The study, “Surge of neurophysiological coupling and connectivity of gamma oscillations in the dying human brain”, was authored by Gang Xua, Temenuzhka Mihaylova, Duan Li, Fangyun Tian, Peter M. Farrehi, Jack M. Parent, George A. Mashour , Michael M. Wang and Jimo Borjigin.