The headline above comes from an August 12 CBS News report (http://is.gd/53gSTe), which continued:
“The brain remains conscious after the heart stops beating, according to University of Michigan researchers. It may even function higher in the moments immediately following cardiac arrest than it does when the body is in a normal state.
The finding supports the shared experience of nearly 20 percent of people who have survived cardiac arrest. These survivors report having internal visions and heightened perception, known as near-death experiences, but the scientific reality of the experience has long been debated.
In a study published Monday in the Proceedings of the National Academy of Science, the team explains that in a study of nine rats, they observed continued brain activity even after the heart stopped beating and blood flow ceased. Compared to anesthetized and waking states, brain activity and coherence actually increased immediately following cardiac arrest. While the sample size is small, the results were observed in all nine of the rats studied.”
The findings, which shed light on the continuing debate over how and whether the dying brain is capable of generating conscious activity, have been widely reported this week.
The online publication medicalxpress.com says (http://medicalxpress.com/news/2013-08-electrical-signatures-consciousness-dying-brain.html):
“This study, performed in animals, is the first dealing with what happens to the neurophysiological state of the dying brain,” says lead study author Jimo Borjigin, Ph.D., associate professor of molecular and integrative physiology and associate professor of neurology at the University of Michigan Medical School.
“It will form the foundation for future human studies investigating mental experiences occurring in the dying brain, including seeing light during cardiac arrest,” she says.
Approximately 20 percent of cardiac arrest survivors report having had a near-death experience during clinical death. These visions and perceptions have been called “realer than real,” according to previous research, but it remains unclear whether the brain is capable of such activity after cardiac arrest.
“We reasoned that if near-death experience stems from brain activity, neural correlates of consciousness should be identifiable in humans or animals even after the cessation of cerebral blood flow,” she says.
Researchers analyzed the recordings of brain activity, called electroencephalograms (EEGs), from nine anesthetized rats undergoing experimentally induced cardiac arrest.
Within the first 30 seconds after cardiac arrest, all of the rats displayed a widespread, transient surge of highly synchronized brain activity that had features associated with a highly aroused brain.
Furthermore, the authors observed nearly identical patterns in the dying brains of rats undergoing asphyxiation.
“The prediction that we would find some signs of conscious activity in the brain during cardiac arrest was confirmed with the data,” says Borjigin, who conceived the idea for the project in 2007 with study co-author neurologist Michael M. Wang, M.D., Ph.D., associate professor of neurology and associate professor of molecular and integrative physiology at the U-M.
“But, we were surprised by the high levels of activity,” adds study senior author anesthesiologist George Mashour, M.D., Ph.D., assistant professor of anesthesiology and neurosurgery at the U-M. ” In fact, at near-death, many known electrical signatures of consciousness exceeded levels found in the waking state, suggesting that the brain is capable of well-organized electrical activity during the early stage of clinical death.”
The brain is assumed to be inactive during cardiac arrest. However the neurophysiological state of the brain immediately following cardiac arrest had not been systemically investigated until now.
The PNAS abstract concludes:
“High-frequency neurophysiological activity in the near-death state exceeded levels found during the conscious waking state. These data demonstrate that the mammalian brain can, albeit paradoxically, generate neural correlates of heightened conscious processing at near-death.”