Surge of brain activity may explain near-death experience
Itâs called a near-death experience, but the emphasis is on
ânear.â The heart stops, you feel yourself float up and out of
your body. You glide toward the entrance of a tunnel, and a
searing bright light envelops your field of vision.
It could be the afterlife, as many people who have come close
to dying have asserted. But a new study says it might well be a
show created by the brain, which is still very much alive. When
the heart stops, neurons in the brain appeared to communicate at
an even higher level than normal, perhaps setting off the
last picture show, packed with special effects.
âA lot of people believed that what they saw was heaven,â said
lead researcher and neurologist Jimo Borjigin. âScience hadnât
given them a convincing alternative.â
Scientists from the University of Michigan recorded electroencephalogram (EEG) signals in nine anesthetized rats
after inducing cardiac arrest. Within the first 30 seconds after
the heart had stopped, all the mammals displayed a surge of
highly synchronized brain activity that had features associated
with consciousness and visual activation. The burst of electrical patterns even exceeded levels seen during a normal, awake state.
In other words, they may have been having the rodent version of
a near-death experience.
âOn a fundamental level, this study makes us think about the neurobiology of the dying brain,â said senior author and anesthesiologist George A. Mashour. It was published Monday online
by the Proceedings of the National Academy of Sciences.
Near-death experiences have been reported by many who have
faced death, worldwide and across cultures. About 20 percent
of cardiac arrest survivors report visions or perceptions
during clinical death, with features such as a bright light,
life playback or an out-of-body feeling.
âThereâs hundreds of thousands of people reporting these experiences,â Borjigin said. âIf that experience comes from
the brain, there has to be a fingerprint of that.â
An unanswered question from a previous experiment set her down
the path of exploring the phenomenon. In 2007, Borjigin had been monitoring neurotransmitter secretion in rats when, in the middle
of the night, two of her animals unexpectedly died. Upon reviewing the overnight data, she saw several unknown peaks near the time
This got her thinking: What kinds of changes does the brain go through at the moment of death?
Then last year, Borjigin turned to Mashour, a colleague with expertise in EEG and consciousness, for help conducting the
first experiment to systematically investigate the brain after cardiac arrest. EEG uses electrodes to measure voltage
fluctuations in the brain caused by many neurons firing at once.
A normal, awake brain should show spikes depending on what types
of processing are going on; in a completely dead brain, it
When the heart suddenly stops, blood flow to the brain stops
and causes death in a human within minutes. A likely assumption
would be that, without a fresh supply of oxygen, any sort of
brain activity would go flat. But after the rats went into
cardiac arrest, Mashour and his colleagues observed the
âWe saw a window of activity with certain signatures typically associated with conscious processing,â he said.
Those signatures include heightened communication among the
different parts of the brain, actively seen in an awake state. Mashour speculates this could be a marker of consciousness â" in
which the brain integrates disparate aspects of the world,
like visual in one area and auditory in another.
âThe brain kind of gets it all together so we have this unified, seamless experience,â he said.
In the rats, this connectivity went above and beyond the levels
seen during the awake state â" which could possibly explain the hypervivid, ârealer-than-realâ perceptions reported close to
death, Borjigin said.
Scientists are still trying to pin down a clear-cut electrical
marker of consciousness because there are many gray areas â" for instance, being under anesthesia or in a vegetative state or having
âWe donât have any rough and ready way to take a measurement
and assign a meaning to it with regards to conscious content,â
said neurologist Nicholas D. Schiff of the Weill Cornell Medical College, who was not involved in the study.
Borjigin also noted an increase in a certain type of EEG pattern
that has been tied to visual stimulation in humans that could possibly explain the very bright light that survivors describe.
âMy hypothesis would be that during the near-death process,
the visual process is highly activated,â she said.
The researchers also confirmed the effect using another form
of death, asphyxiation via carbon dioxide inhalation. The same
highly aroused features were seen in a nearly identical pattern.
Schiff finds the study âvery interestingâ and novel but is
skeptical about any near-death interpretations.
âThereâs no intrinsic reason to believe that these rats are in
some heightened state of awareness,â he said. He believes the
spike in activity is simply a shock-to-the-system response by
the brain cells to a major change in physiology.
âThe majority of near-death experiences cannot be explained by such
a study,â said radiation oncologist and near-death researcher
Jeffrey Long, who thinks it is another in a long line of possible scientific explanations that havenât panned out.
The EEG surge fails to explain the out-of-body feeling and
reuniting with long-lost loved ones reported by many, he said.
Long, a skeptic-turned-believer, has been researching near-death moments for more than 14 years. He set up the Near Death
Experience Research Foundation, which has collected more than
3,000 accounts from survivors around the world.
Borjigin and Mashour hesitate to state a direct connection
between their findings and near-death experiences. The links
are merely speculative at this point and provide a framework for
a human study, Borjigin said.
Even if the EEG patterns after cardiac arrest appear similar to
the those of the awake state, Schiff cautioned that the same interpretation may not be possible because the brainâs playing
field has changed drastically because of lack of blood flow. He
does think that this surge in activity recorded in rat brains
would probably be similar in humans.
Some case reports by doctors describe similar EEG sequences in
their patients at the point of death, but no systematic study
has been done.
By Meeri Kim, Published: August 12, 2013
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