You are probably no stranger to the fact that people who have come back from the verge of death have said that it was as if ‘their whole life flashed before their eyes.’
Very recently, unusual research into brain activity just before death offers clues about why such experiences occur.
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.