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Tuesday, September 3, 2013

Explaining near death experiences

Many people claim to have had near-death experiences (NDEs). About 20% of cardiac arrest survivors alone report having had some sort of experience while they were clinically dead. There has been much speculation about the validity and the meaning of NDEs, especially since they are commonly described as being extremely vivid, or even ‘more real than real’. Now, researchers led by Jimo Borgigin of the University of Michigan may have a physiological explanation for the phenomenon.

The scientists hooked nine rats up to electroencephalograms (EEG). The rats’ brain waves were recorded during normal wakefulness, anesthesia, and induced cardiac arrest (caused by intracardiac injection of potassium chloride). Cardiac arrest was timed from last heartbeat to loss of oxygenated blood. In other words, I’m sorry to say that the animals were not revived.

All nine rats’ showed the same patterns of brain activity that were distinct during the three different cognitive states. Three seconds after the onset of the cardiac arrest, the rats’ brain waves diverged from either the wakeful or anesthetized patterns. As the arrest progressed, there were surges of highly synchronized activity indicative of a greatly aroused brain. 

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.
If these results apply to humans as well as rats, NDEs may very well be real phenomena that are created by an overactive brain in the throes of death. Of course, we can’t know what the rats were experiencing. That is, did they experience the rat equivalent of an NDE complete with vivid imagery, or was the increased brain activity merely irrelevant background noise? The only way to really apply this data to NDEs would be to perform the experiments on humans, which would pose some ethical problems, to say the least.
You can listen to more about this story on this episode of Skeptics’ Guide to the Universe, starting at 5:15.

Borjigin J, Lee U, Liu T, Pal D, Huff S, Klarr D, Sloboda J, Hernandez J, Wang MM, & Mashour GA (2013). Surge of neurophysiological coherence and connectivity in the dying brain. Proceedings of the National Academy of Sciences of the United States of America PMID: 23940340.