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Signs of Consciousness in Dying Brains

A brief burst of brain activity with the neural signatures of consciousness follows cardiac arrest in rats. 

By | August 13, 2013

FLICKR, VESTMAN

Neuroscientists have recorded intense bursts of neural activity, lasting about 30 seconds, in rats after experimentally stopping their hearts. The researchers claim that the after-death brain activity is associated with a heightened conscious experience and may be a neural correlate of near-death experiences—a suite of euphoric, hyper-real experiences reported by nearly 20 percent of cardiac arrest victims. The findings were published Monday (August 12) in the Proceedings of the National Academy of Sciences.

The University of Michigan researchers, led by Jimo Borjigin, implanted six electrodes each into the brains of nine rats, gave the animals lethal injections of potassium chloride, and measured neural activity as they died. Immediately after the rats’ hearts stopped, the electrodes measured a sustained doubling of synchronized, high-frequency brain activity called gamma waves, which have been implicated in connecting perception and awareness to produce the experience of consciousness.

“By presenting evidence of highly organized brain activity and neurophysiologic features consistent with conscious processing at near-death, we now provide a scientific framework to begin to explain the highly lucid and realer-than-real mental experiences reported by near-death survivors,” wrote Borjigin’s team.

“It shows us in considerable more detail than ever done before what happens when the brain is dying,” Christof Koch, a neuroscientist at the Allen Institute for Brain Science in Seattle, told NPR. “The brain doesn't immediately go off, but it shows a series of sort of complicated transitions.”

Similar neural signatures have never been found in dying humans who have been hooked up to electroencephalography devices. Borjigin told Wired that the signals they observed in rats were rather weak and may not have registered in EEG records of human patients because those measurements are taken from electrodes placed on the scalp, not the brain itself.

Other scientists were not convinced that the study revealed anything about what happens in the human brain following death.

Sam Parnia, a critical care physician at Stony Brook University and director of the Human Consciousness Project’s AWARE study, which documents near-death experiences, urged caution in interpreting the findings.

“I don't think that this particular study helps in any way to explain near-death experiences in human beings,” Parnia told NPR. “We have no evidence at all that the rats had any near-death experiences or whether animals can have any such type of experience, first of all.”

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Comments

Avatar of: platonica

platonica

Posts: 2

August 14, 2013

"gamma waves, which have been implicated in connecting perception and awareness to produce the experience of consciousness"

hmmm... really? how exactly? ... that is just mumbo jumbo

 

Like Sam Parnia says, this study tells us nothing.

It is just a record of the brain wave response to dying after a lethal injection of KCl.

 

 

Avatar of: Nerdsauce

Nerdsauce

Posts: 1

August 15, 2013

hmmm... really? how exactly? ... that is just mumbo jumbo

Nice response, love the way you used facts to back up your view that this is "mumbo jumbo", and this entire study shows us "nothing". Neuroscientist, are we? No? Then how do you know gamma waves are mumbo jumbo? How do you know this study shows nothing?

Personally, I find this fascinating - and I'm keen to see if they can detect similar brain activity in a human brain upon death. At the very least, this study shows "brain death" isn't the simple "switch off" we thought it was, and that the brain actually goes through a complex series of events before finally going dark once and for all.

Avatar of: Yceb

Yceb

Posts: 1

August 15, 2013

What I think it is is that if the brain has evolved to ultimately survive, it must have a mechanism of "wake up and overstimulate all neural centers" upon a detection that death is imminent, just to have a last chance of keeping alive just in case something in the body is failing because some neural center malfunctions or it's damaged and another neural center can take over that. 

The fact that this mechanism exists and it's hardwired means that, evolutively, it has been useful for survival, so it has worked in many cases along all the species procreation. Maybe an organism with problems experiences this process several times and can avoid death in certain cases, prolongating the chances of that organism to reproduce.

In fact we, humans, have this same mechanism based upon the experiences of terminal patients reported by familiars and investigators, when many dying persons have had a spike of strong lucidness moments before death.

Avatar of: mightythor

mightythor

Posts: 44

August 16, 2013

Needs to be replicated with other mechanisms of death, to rule out that it is a KCl effect.  Should be easy.  I'm sure scientists have figured out thousands of ingenious ways to kill lab rats.

Avatar of: silver

silver

Posts: 1

August 17, 2013

potassium chloride? You must be kidding.

That's a ion not a molecule that binds specifical histologic districts. By saturating the extracellular environments with IV potassium you're affecting everyting.

Besides, potassium is deeply involved in neural transmission.

Not exactly what one may wish for when checking for natural EEG activity duh!

Avatar of: discgolfdc

discgolfdc

Posts: 2

August 20, 2013

Potassium chloride is not an ion, but a salt. It does dissociate into ions, however.
Avatar of: discgolfdc

discgolfdc

Posts: 2

August 20, 2013

And salts are, by definition, molecules.
Avatar of: Electro

Electro

Posts: 1

August 20, 2013

Using KCL simply caused the neurones to depolarise and fire a high frequency train of action potentials: This is not related to "near death". As suggested by others the cardiac arrest should be caused by another mechanism . Potassium is known to regulate the membrane potential of neurons  and muscle cells therefore increasing extracellular levels will of course cause death due to arrest of heart muscle (which depolarises) and a parallel depolarisation of neurones.

It is likely that other mechanisms may increase neuronal activity transiently by reducting available ATP, reducing the Na/K pump activity and depolarising nerve cells, bring them closer to the firing threshold for producing action potentials.

Avatar of: Prof Bókkon

Prof Bókkon

Posts: 1

August 23, 2013

Bókkon I, Mallick BN and Tuszynski JA (2013). Near death experiences: A multidisciplinary hypothesis. Front. Hum. Neurosci. 7:533. doi: 10.3389/fnhum.2013.00533. 

Here is the link:
http://www.frontiersin.org/Human_Neuroscience/10.3389/fnhum.2013.00533/abstract
You can also download provisional PDF of this paper at this link.

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