An
analysis of brain activity was carried out in seven sedated, critically
ill
patients as they were removed from life support. Using
EEG recordings of neural
electrical activity, a brief but significant spike
was observed at or near the
time of death—despite a preceding loss of blood pressure and
associated drop in
brain activity.
What is unusual with this is that it
occurs at a
very peculiar time point near death, when most people would think that
the brain
would physiologically die because of an absence of blood to the brain.
The
jolts lasted 30 to 180 seconds and displayed properties that are normally
associated with consciousness, such as extremely fast electrical oscillations
known as gamma waves. Soon after the activity died down (pardon the pun),
the
patients were pronounced dead.
The researchers who carried out this
study think
that the predeath spikes are most likely brief, “last hurrah” seizures
originating in brain areas that were irritable from oxygen starvation.
Living
nerve cells constantly maintain an electrical charge gradient, similar
to the
difference in charge on the poles of a battery. Keeping up this
polarity takes energy—in
this case, energy created from oxygen. As blood flow slows and oxygen
runs out,
the cells can no longer maintain polarity and they fire, causing a
cascade of
activity that ripples through the brain. If these seizures were to
occur in
memory regions, they could explain the vivid recollections often
reported by
people who are brought back from near death.
It
is difficult to draw further conclusions because in these patients only
the
forebrain was monitored. The end of a person’s is a poorly researched
area –
not surprisingly given the ethical red tape that you would have to go
through
to get permission to do these studies. However, the scientists are
hoping to
use more sophisticated brain imaging on a larger patient population to
assess
the entire brain in greater detail during near-death episodes.
References:
Lakhmir
S.
Chawla, Seth Akst, Christopher Junker, Barbara Jacobs, Michael G.
Seneff. Surges
of Electroencephalogram Activity at the Time of Death: A Case Series. Journal
of
Palliative Medicine. December 2009, 12(12): 1095-1100.
Peter
Sergo. Going out with a Bang.
Scientific American Mind. May/June 2010, volume 21(2), 10.
It
is difficult to draw further conclusions because in these patients only
the
forebrain was monitored. The end of a person’s is a poorly researched
area –
not surprisingly given the ethical red tape that you would have to go
through
to get permission to do these studies. However, the scientists are
hoping to
use more sophisticated brain imaging on a larger patient population to
assess
the entire brain in greater detail during near-death episodes.