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Article 6375 of comp.ai.philosophy:
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>From: bill@nsma.arizona.edu (Bill Skaggs)
Newsgroups: comp.ai.philosophy
Subject: Intelligence without a brain?
Summary: It's a myth.
Message-ID: <BILL.92Jun26113658@cortex.nsma.arizona.edu>
Date: 26 Jun 92 18:36:58 GMT
References: <9908@scott.ed.ac.uk> <J1HymB2w164w@cybernet.cse.fau.edu>
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Organization: ARL Division of Neural Systems, Memory and Aging, University of
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In-Reply-To: justin.bbs@cybernet.cse.fau.edu's message of 26 Jun 92 03: 25:06 GMT

justin.bbs@cybernet.cse.fau.edu writes:

   In Michale Talbott's BEYOND THE QUANTUM he cites cases of individuals who 
   are born effectively without a brain, only a thin membrane essentially 
   surrounding the area where the brain should be.

Over the past couple of years I've heard this story a dozen times.  It
seems to have become an urban myth, along the lines of the "thousand
monkey" story, the "you lose a thousand brain cells every day of your
life" story, and the "you only use ten percent of the capacity of your
brain" story.

The fact it is based on is that there are people with hydrocephaly who
have normal intelligence.  In hydrocephaly the flow of cerebro-spinal
fluid in the brain is blocked, so that it builds up and its pressure
increases.  In young children, whose skulls are still soft, this can
cause the head to gradually increase in size, sometimes to a grotesque
degree.  While this is happening, the ventricles -- cisterns of fluid
inside the brain -- also increase in size, turning the tissue of the
brain into a relatively thin layer between the (enormous) ventricles
and the skull.  (The condition is now pretty rare, because it can
routinely be treated by installing a "shunt" in the brain.)

The thing is that the "thin layer" is actually quite broad, and may be
comparable in total volume to a normal brain.  Suppose, for example,
the normal brain were a sphere five inches in diameter.  If this were
blown up to a sphere ten inches in diameter, the original brain would
have the same volume as a spherical shell less than a quarter inch
thick.  (Work it out!)

To my knowledge, there exists no report of a patient with normal
intelligence being brought to autopsy and his/her brain tissue being
found to have dramatically less volume than normal.  (Brain scans,
such as MRI, cannot be trusted because their interpretation is based
on the fluid content of the tissue, which is bound to be abnormal in a
hydrocephalic patient.)

	-- Bill

(Note 1:  There is another condition, called "anencephaly", in which
children really are born essentially without a brain, but such people
are invariably profoundly retarded -- basically lacking all but the
most primitive reflexes.)

(Note 2:  I don't think this topic is particularly appropriate to
comp.ai.philosophy, so I won't follow up on any responses; but I'll be
happy to correspond by Email.)


