From: ae553@yfn.ysu.edu (David Jameson)
Subject: Re: Near Death Experiences
Reply-To: ae553@yfn.ysu.edu (David Jameson)
Organization: St. Elizabeth Hospital, Youngstown, OH
Date: Fri, 16 Oct 1992 07:39:51 GMT


In a previous article, mcgrath@cs.uiuc.edu (Robert McGrath) says:

>In article <1992Oct14.123406.10213@news.ysu.edu>, ae553@yfn.ysu.edu (David Jameson) writes in part:
>|> >|> neurons to keep firing even after being deprived of oxygen for a few
>|> >|> minutes?  This would apply for all the NDEs i.e. if the "light at the
>|> >|> end of the tunnel" is purely a result of brain activity then obviously
>|> >|> a lot of neurons will need to be firing -- would this be possible when
>|> >|> the oxygen supply to the brain has been shut off?
>|> >Yes, definitely.  In fact, this is a very likely physiological model of
>|> >the NDE.  And from what is know of comas, people can receive information
>|> >from their ordinary senses, even though they are apparently unconscious
>|> >for a long time.  So, you don't have to invoke ESP to account for people
>|> >hearing conversations when they are unconscious, this is know to
>|> >happen through the ears.  (This is why well trained nurses are very
>|> >polite, kind, and positive to folks in comas--they know that if and
>|> >when the patient wakes up they might well remember.)
>|> 
>|> Are you sure about this?  In a coma this wouldn't be any problem but
>|> are you sure that the brain can function for extended periods without oxygen?
>|> e.g. after a heart-attack.  In the programme, one surgeon said it was
>|> impossible.  I don't know whether this is true or not as I'm not a
>|> neurobiologist.
>I wasn't very clear.  There are several claims all mushed together here.
>
>I was claiming that a patient in a coma can sometimes receive 
>information from outside.  This is fairly well established, although 
>I don't know that neurologists really understand how this might happen.
>
>I also claimed that brain activity can continue for at least a while 
>with oxygen cut off.  This is clearly possible, as it happens all the 
>time when people are resucitated from heart failure.  Naturally, there 
>may be damage, and the experience may be wierd....
>
>In addition, I was drawing an inference:  if people can receive info
>while in a coma, and if brain function can continue during heart
>failure, then it seems reasonable that the brain could sometimes get
>info about the world while dying for lack of oxygen.  I think this
>is a reasonable speculation, and I think it well might account for
>some of the things that people "see" in NDEs.
>
>One wonders exactly what the surgeon was trying to say.  Is 10
>or 15 minutes an "extended period"?  People often are revived 
>that long after drowning or heart failure.
>

You seem to have missed the point of my question.  You simply stated
that the brain can survive without oxygen for a limited time, but I
was asking whether the brain can actually function without a supply
of blood (something totally different).

It is possible for neurons to survive for between about three and ten
minutes after the blood supply has been shut off, but just because they
haven't died doesn't necessarily mean they can still function.
For a neuron to operate there needs to be an energy supply in the form of
glucose, which is supplied by the blood.  Cut off the blood supply and you
deprive the neurons of the energy necessary to transmit signals.  The only
way neurons could possible operate in this situation would be if they
stored large amounts of glucose somewhere.

Consider, for example, a person fainting.  For some reason or another, the
brain isn't getting enough oxygen and the person gradually begins to lose
consciousness.  First there is a loss of sound and then a loss of vision,
followed by loss of consciousness if the situation continues.  When the
person recuperates there is no brain damage, but while the person was
unconscious certain parts of the brain were unable to function because
of lack of oxygen.  If not (i.e. if the brain can continue to function,
as you seem to be implying), why did the person lose consciousness in the
first place?

Dave.
-- 
 ------------------------------------------
| David Jameson, Email : ae553@yfn.ysu.edu |
 ------------------------------------------
Newsgroups: alt.out-of-body