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Article 2365 of comp.ai.philosophy:
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>From: harwood@umiacs.umd.edu (David Harwood)
Newsgroups: comp.ai.philosophy
Subject: Re: Scaled up slug brains
Message-ID: <45350@mimsy.umd.edu>
Date: 22 Dec 91 18:13:45 GMT
References: <12788@pitt.UUCP> <45210@mimsy.umd.edu> <12804@pitt.UUCP>
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In article <12804@pitt.UUCP> geb@cs.pitt.edu (Gordon Banks) writes:
>In article <45210@mimsy.umd.edu> harwood@umiacs.umd.edu (David Harwood) writes:
>>issue of handedness in monkeys, for example. I have not heard of
>>lateralization related to spatial function in animals, such as you
>>describe, related to territoriality. You see a big difference, though,
>>don't you? There is very direct psychological and neurological evidence
>>for laterization of function in humans, in many respects. You have not
>>(so far) made evidently clear what kind of function is supposed to
>>be involved, or what you mean by "lateralization." Also, in my other
>
>Actually, I don't see a big difference.  Lateralization is just another
>form of brain specialization that occurs in other areas.  There is plenty
>of neurological and psychological evidence that it occurs in other
>species.  There is also a lot of evidence that the strength of the
>lateralization is dependent on fetal androgens both in animals and in
>humans.  In animals, spatial cognitive functions are the lateralized
>ones.  In humans, both spatial and language.  
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	I don't disagree with this, but it is not quite an answer to what
I asked. (I think brain specialization in humans is marked; as I have
observed we have several unusual features: expressive faces, vocal cords
and complex speech production and recognition, color vision, great
dexterity - these are qualtitative features, they involve a lot of the
human brain; they all are manifest very early on. They do not even exist
in slugs.)
	I want to clarify something else - circuits in the brain involve
physically and functionally different kinds of neurons; circuits are not
simply formed as in NN models by modifying links and coefficients; rather 
curcuits are formed among types of cells according to a chemical code:
a cell of type A recognizes and accepts a link to a cell of type B. There
are many types of cells and circuits. They are not ordinarily interchange-
able. (It would be  profoundly useful medically if they were; especially
if animal cells and neurons could be grafted into our brains; of course
some people have propose grafting human fetal tissue or even tissue from
clones. Some attempts at brain injection have been successful, others 
have failed, according to what little I have read about it.)
	But what bothers me about replying to you is that you do not
quite reply to what I asked? You referred to the work of a colleague,
and I asked (not as a criticism) what was the connection between 
territoriality and spatial perception vis a vis lateralization. You did
not answer. Would you simply give me a reference to a publication, and
I will be happy to read for myself?
	(I previously referred to effects of sex hormones on brain
development; I recall that there is some controversial evidence in humans
that certain human spatial abilities are sex-linked.)
	What is the role of sex-hormones in neonatal development of the
two animals - one territorial and spatially lateralized, the other not?

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>
>I am a human neurologist and know very little about birds.  I know
>these things about mammals because they bear on human brain function.
>The further away you get from humans the more different the brains
>are, obviously.  In your own field, you are undoubtedly aware that
>bird vision is primarily tectal.
\\\\\\\\\\\\\\\\\
	So you agree that mammals are not "scaled-up" slug brains,
anymore than they are not "scaled-up" bird brains? I think there is
some hope here.
\\\\\\\\\\\\\


>
>>of brain functions" (as you quote me). I am still not aware that other
>>species show such pronounced lateralization of function as do humans
>>ordinarily. (This is not to say that humans cannot use or repair to
>>use both hemispheres, to some degree, with difficulties sometimes.)
>
>Actually, the right hemisphere is capable of taking over language functions
>in some people.  In women and left-handed people, this is much more
>likely.  After a stroke which damages Broca or Wernicke's areas, 
>some patients will have recovery of language function.  A second
>stroke damaging the corresponding areas in the right hemisphere
>will wipe out language permanently.
\\\\\\\\\\\
	I would be interested to read any of your publications in
your field of human neurology, which you feel might be relevant to
our discussion. (Mine are in computer science in the fields I mentioned,
except for two or three many years ago in the psychology of language.)
	Yes - but don't these patients, unless they are very young,
have difficulties? And even if they are older, don't they often fail
to recover their full language abilities? And don't many people who
fail to show "normal" lateralization in various respects also often
show various linguistic disabilities? And aren't isn't there some
lesser verbal processing by the right brain even in "normal" people?
And don't people with major parts of right hemispheres damaged or
surgically removed still have relatively normal verbal abilities and
reasoning, while the opposite is disastrous, even detroying apparent
self-conscisoness?
	(There are many people showing variations in lateralized brain
function, and they are not necessarily less intelligent or permanently
linguistically disabled. In fact, such (genetic) variations could be 
advantageous in some respects. For example, possibly Einstein may have 
been somewhat dislexic, and verbally retarded as a very young boy, and
while his mathematical skills perhaps were not outstanding (see his
correspondence with mathematicians; he even had assistants to help him
mathematically), his spatial/geometrical and physical/kinesthetic
intuitions were extraordinary. It could be that there are trade-offs.)





