The brain surges with activity just before death

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Scientific American

Mind - April 27, 2010

Going Out with a Bang

The brain surges with activity just before death

By Peter Sergo

 

 

 

 

 

People who are resuscitated from near death often report strange

sensory phenomena, such as memories âflashing before their eyes.â

Now a rare assessment of brain activity just before death offers clues

about why such experiences occur.

Anaesthesiologist Lakhmir Chawla of George Washington University

Medical Centre and his colleagues recently published a retrospective

analysis of brain activity in seven sedated, critically ill patients as

they were removed from life support. Using EEG recordings of neural

electrical activity, Chawla found a brief but significant spike at or

near the time of deathâdespite a preceding loss of blood pressure and

associated drop in brain activity.

âTo our knowledge, this is the first time that this event has been

shown to occur,â Chawla explains. âIt occurs at a very peculiar

time point, when most people would think your brain would

physiologically die [because of] an absence of blood flow.â

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

abated, the patients were pronounced dead.

Chawla posits that the pre death spikes are most likely brief,

âlast hurrahâ 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

energyâin 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 resuscitated from

near death, Chawla says.

Further speculation is difficult because in these patients only the

forebrain was monitored, notes Chawla, adding that the end of life is a

poorly researched area. Next he and his colleagues would like to use

more sophisticated imaging on a larger patient population to assess the

entire brain in greater detail during near-death episodes.