The brain continues to work for up to 30 seconds after the heart stops beating, according to a new study from the University of Michigan.
Using anesthetized lab rats, researchers induced cardiac arrest and watched the rats' brain activity, observed in electroencephalograms (EEGs). For 30 seconds after blood flow stopped, there was a flurry of brain activity indicating a highly aroused mental state, according to the study published in the Proceedings of the National Academy of Sciences.
The brain activity they observed was characteristic of conscious perception.
What does this mean about the last moments of life?
Scientists said Monday the brain activity could explain vivid near-death experiences. About 20 percent of those who experience cardiac arrest report some kind of near-death experience while they are “clinically dead.”
“We were surprised by the high levels of activity,” said senior author of the study George Mashour, a professor of anesthesiology and neurosurgery at the University of Michigan. “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 study is a landmark finding in the neuroscience of dying.
“This study, performed in animals, is the first dealing with what happens to the neurophysiological state of the dying brain,” said lead 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 said.
While there are reports of near-death experiences, there was no previous evidence that the human brain was capable of such activity.
“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 said.
Until now there has been no systematic study of the brain after cardiac arrest.
“This study tells us that reduction of oxygen or both oxygen and glucose during cardiac arrest can stimulate brain activity that is characteristic of conscious processing," she said. "It also provides the first scientific framework for the near-death experiences reported by many cardiac arrest survivors.”