Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!leah!itsgw!steinmetz!uunet!sco!carolf
From: carolf@sco.COM (Carol Freinkel)
Newsgroups: comp.ai.neural-nets
Subject: Flexibility of nervous systems
Message-ID: <2400@scolex.sco.COM>
Date: 6 Mar 89 20:14:20 GMT
Distribution: usa
Organization: The Santa Cruz Operation, Inc.
Lines: 48


In article <11945@swan.ulowell.edu> sbrunnoc@hawk.ulowell.edu (Sean Brunnock) writes:
>the human brain is pretty much uniform. This 
>fact becomes dramatically obvious in the cases of people who have
>had accidents resulting in the damage of sections of the brain.
>If the damaged section performed a specialized function, then
>for awhile, the person will not be able to perform that action.
>After some time, the rest of the brain is able to assimilate
>the functions performed by the damaged section and the person
>is able to function normally again. 

This is only partially true.  There are many areas of the brain 
which cannot be replaced if damaged.  If the vision-processing
region at the back of the brain is removed, the person will be
blind.  Also, if both sides of the hippocampus are removed, the
person will not be able to retain long-term memory anymore.
(This operation was performed only once.  When the damage this
causes was realized, it was never done again.  I read about this
case in a neurobiology class.  This man lives in a perpetual
present.  If you were to visit him, leave the room, and walk back
in, he wouldn't know you.)  And the human brain is definitely
*not* uniform.  There is an elaborate architecture on both the
macroscopic and microscopic level.  The list of names which
describes these structures is frighteningly long.

There are many areas of the brain which are mostly
inflexible.  On the other hand, it is true that people can
sustain large amounts of damage to the frontal lobes with
(apparently) minimal effects.  Also, some children born with
brains compressed/damaged from hydrocephaly (water on the brain)
are quite intelligent.  When damage occurs at a younger age,
adapation is more likely to occur.

Generally speaking, animals with larger brains have more
flexibility.  If the eye of a newt is rotated, the newt will
perpetually move its head up to reach food which is below it and
vice versa.  When this experiment was done on kittens, the
kittens eventually adapted to the change and were able to move
appropriately.  With some animals, the circuitry is essentially
"hard-wired."  (As one anatomy professor put it, there might as
well be pulleys and levers in there.)  Creatures with more complex 
nervous systems have more flexibility and possibility of
"reprogramming."


Carol Freinkel
carolf@sco.COM
...!uunet!sco!carolf