A recent study published in the Proceedings of the National Academy of Sciences has presented preliminary findings suggesting there can be a surge of brain activity linked to consciousness during the dying process.
The new study aimed to investigate 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 highly vivid and real-like experiences. These experiences challenge our understanding of brain function during cardiac arrest when consciousness is believed to be absent.
Previous research has shown that high-frequency brain oscillations, specifically gamma activities, are associated with consciousness. In animal studies, sudden termination of cardiac function or acute asphyxia has been found 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 discover the surge of gamma oscillations in the dying process, in rats (Borjigin et al., 2013; Li et al., 2015), as I was shocked to realize that the science/medicine knows little about the brain during the dying process,” said study author Jimo Borjigin, an associate professor in the department of Molecular and Integrative Physiology with a joint appointment in Neurology at University of Michigan Medical School.
Gamma oscillations are rhythmic patterns of neural activity that occur in the gamma frequency range, typically ranging 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 believed 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 role of the brain during cardiac arrest may 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 from cardiac arrest while under EEG monitoring. These patients were comatose and unresponsive and were determined to be beyond medical help. With the families’ permission, ventilator support was withdrawn.
Two of the patients showed an increase in heart rate and a surge of gamma wave activity upon removal of life support. This activity was observed in the “hot zone” of the brain associated with consciousness, specifically the junction between the temporal, parietal, and occipital lobes.
The research raises the possibility that patients who are experiencing cardiac arrest, and therefore considered clinically dead, may still possess some level of consciousness that is not externally visible or detectable.
“The high levels of organized brain activity remaining in the seemingly comatose patients suggest there are much to be learned about the brain of comatose patients, as they may not be beyond the help of future medicine,” Borjigin told PsyPost.
The findings indicate that the withdrawal of ventilator support can stimulate a transient and widespread surge of gamma activities in certain patients near death. These gamma activities include various features such as increased gamma power, coupling of gamma oscillations with slower oscillations, functional and directed connectivity within the brain, and communication between different brain regions.
According to Borjigin, the study provides evidence that “the human brain can be activated by the dying process.”
“The activated brain shows neural signatures of consciousness. Therefore, NDE is highly 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. Additionally, since the patients did not survive, it is impossible to know what subjective experiences they may have had, if any.
“We found the gamma surge in 2/4 patients. Data from more dying patients need to be analyzed to see how common this surge is among the comatose dying patients,” Borjigin said.
The researchers said that larger, multi-center studies involving ICU patients with EEG monitoring who survive cardiac arrest could provide further insights and data to determine whether these bursts of gamma activity indicate hidden consciousness even near death. Studying the dying process, specifically cardiac arrest, could offer valuable insights into the mechanisms underlying human consciousness, they added.
“I am very optimistic that the neural basis of 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.