There may be a scientific explanation for the vivid
near-death experiences, such as seeing a shining light, that some people report
after surviving a heart attack, US scientists said.
Apparently, the brain keeps on working for up to 30 seconds
after blood flow stops, according to a study published in the Proceedings of the National Academy of
University of Michigan scientists did their research on nine
lab rats that were anesthetised and then subjected to induced cardiac arrest as
part of the experiment.
How the study was
In the first 30 seconds after their hearts were stopped,
they all showed a surge of brain activity, observed in electroencephalograms
(EEGs) that indicated highly aroused mental states.
"We were surprised by the high levels of
activity," said senior author George Mashour, 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."
Similar results in terms of brain activity were seen in rats
that were asphyxiated, the researchers said.
"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," said lead author Jimo Borjigin.
"It also provides the first scientific framework for
the near-death experiences reported by many cardiac arrest survivors."
About 20% of people
who survive cardiac arrest report having had visions during a period known to
doctors as clinical death.
Mainstream science has long considered the brain to be
inactive during this period.
Borjigin said she hopes her team's latest study "will
form the foundation for future human studies investigating mental experiences
occurring in the dying brain, including seeing light during cardiac