MadSci Network: Neuroscience

Re: Does the brain continue to live after decapitation?

Date: Wed Mar 29 17:58:28 2000
Posted By: Ed Bartlett, Post-doc/Fellow, Neuroscience, University of Wisconsin-Madison
Area of science: Neuroscience
ID: 948325735.Ns

I apologize that I took so long to answer your question.The answer is that 
if a person can perceive sensation or think after decapitation, these 
perceptions or thoughts only persist for about 5-30 seconds. This estimate 
is based on two pieces of evidence. First, deprivation of oxygen to the 
brain for about 10 seconds causes a loss of consciousness in humans, at 
which point there is no conscious perception. 

Second, studies in rats have investigated the persistence of electrical 
brain activity after decapitation using an electroencephalogram (EEG). 
These studies were originally performed to determine whether decapitation 
was a humane method of killing the animal without anesthetic. These 
techniques are occasionally necessary to avoid the effects of anesthetics 
on the body tissue being studied.  By 30 seconds after decapitation, there 
was no electrical activity, indicating complete brain death. However, up to 
15 seconds following decapitation, it was found that  electrical activity 
similar to that in the waking brain or during the rapid-eye movement (REM) 
phase of sleep was present. 

It is somewhat difficult to interpret this activity. The EEG signal in 
waking or REM sleep is characterized by different regions of the brain 
working asynchronously (out of phase)and at higher frequencies, whereas 
deep sleep is characterized by synchronous (in phase) and lower 
frequency activity throughout the brain. However, when neurons are injured,  
which would likely occur following decaptitation, they often respond with a 
higher frequency discharge of electrical activity. It is possible that this 
is the response observed in the post-decapitation EEG. Concerning 
perception and thought during the 15 seconds in which waking-like EEG 
activity is present, I can suggest a grisly experiment that could attempt 
to answer the question. In normal animals, sensory activation such as a 
light or sound will cause a noticeable change in the EEG activity over the 
appropriate portion of the skull. So if the animal could be decapitated 
while recording EEG responses to sensory stimuli, it might be able to 
address whether the animals can still sense for a few seconds.   

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