From: mcochran@nyx.cs.du.edu (Mark A. Cochran)
Subject: Re: Spoken Like a True ProLifer
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Date: Sun, 10 Jan 93 15:14:53 GMT

In article <1993Jan9.005134.29659@organpipe.uug.arizona.edu> sfm@manduca.neurobio.arizona.edu (Stephen Matheson) writes:
>From article <1993Jan8.222739.20331@mnemosyne.cs.du.edu>,
>by mcochran@nyx.cs.du.edu (Mark A. Cochran):
>> In article <1993Jan8.193440.26552@organpipe.uug.arizona.edu>
>> sfm@manduca.neurobio.arizona.edu (Stephen Matheson) writes:
>>>From article <1993Jan6.200941.13165@mnemosyne.cs.du.edu>,
>>>by mcochran@nyx.cs.du.edu (Mark A. Cochran):
>>>> In article <1993Jan6.183814.1552@organpipe.uug.arizona.edu>
>>>> sfm@manduca.neurobio.arizona.edu (Stephen Matheson) writes:
>>>>>From article <1993Jan6.162256.4767@mnemosyne.cs.du.edu>,
>>>>>by mcochran@nyx.cs.du.edu (Mark A. Cochran):
>>>>>>>=vengeanc
>
>> I think we can state that we *do* know that the brain is necessary for
>> thought. For evidence, consider what happens to victims of cerbral
>> trauma. Or look back at the records of patients who were lobotimized.
>> Consider the alterations in thought processes brought on by
>> glioblastomas, neuroblastomas, etc. Gien tha tthese are affecting the
>> brin, and nothing else, there is no reason not to conclude that the
>> brain is necessary for thought.
>
>Yes.  My use of "necessary" rather than "sufficient" makes your
>point true, somewhat obviously.
>
>> We don't "know" when the fetal brain is sufficiently developed to
>> allow thought. We can, however, make some resonable and logical
>> theories about it.
>
>Your use of the word 'theories' in this context is correct, rare,
>and much-appreciated (at least by me).
>
>> Given that myelination is necessary for proper
>> conduction of impulses in the brain
>
>Just how "given" is this?  Before myelination, aren't most fibers
>nevertheless conducting impulses, albeit much more slowly than after
>myelination?  I'm going to go check this, but I'm rather sure at this
>point that myelination speeds conduction rather than making it possible
>(that's the job of ion channels).  Pre-myelinated fibers, in at least
>some cases, are just as competent to have excitable membranes.
>
Premylinated fibers do conduct some impulses, certainly. They are, as
you pointed out, conducted at a much slower rate. They are also (if I
remember my neuro) subject to transmission failure at a fairly high
rate. 
As an analogy, consider the conversation we are having. If every third
line were dropped, or if random words were deleted, it would no longer
bear any resemblance to rationality.
How could we have rational thought with the same random loss of
impulses?

>> (exam record of patients who have
>> been demylinated for supporting evidence)
>
>Here I can say with confidence: a demyelinated fiber is not the same
>as a premyelinated fiber.  A demyelinated fiber cannot conduct because
>the myelination led to the concentration of sodium channels at the
>nodes.  Removal of the myelin leaves the fiber with widely-separated
>islands of excitable membrane, with no way to regenerate the impulse
>in between.  I believe that some function is regained in chronically
>demyelinated fibers, due to the gradual spreading of the ion channels
>throughout the membrane.  At this point, it becomes similar to a
>premyelinated fiber: capable of conduction, but at a slower velocity
>than in the myelinated condition.
>
A weak analogy on my part, admitedly. However, in the case you cite,
that of chronically demylinated fibers, it should be pointed out that
the function regained is sporadic and subject to severe limitations.
I've said before this is out of my field, but my recollection is that
such regained function is limited to gross motor control. I don't
think thought processes would be possible with such limited neural
activity (strictly an opinion, obviously) no matter how "gross" our
thoughts may be, at times. :)

>I have yet to see a solid scientific argument in favor of the
>"thought needs myelin" theory.
>
>> we can theorise that
>> mylination is at least *one* stage of development that needs to be
>> reached before thought can take place.
>
>Theorize to your heart's content; I love to discuss theories.  If
>you want to see me go ballistic, write up your theory as though
>it's a fact, then publish it in the non-peer-reviewed journal
>_Parade_ magazine.  You'd at least get applause from a misguided
>planetary scientist.
>
I don't even *read* _Parade_ so we don't have to worry about this...

>>>> Late term, it has developed the hardware, but has it the
>>>> software? (the experiences, the intereaction with an environment) Late
>>>> term, the issue of sentience (part of my definition of personhood)
>>>> becomes debatable. And it would be necessary to prove the existance
>>>> (not the lack of) that sentience before it could be considered a
>>>> factor in termination of the pregnancy.
>
>>>I think most people would agree that "sufficient reason to doubt"
>>>the absence of sentience would be enough to refuse to pull the
>>>plug on a comatose individual.  If (and I do mean if) we have
>>>sufficient reason to doubt the absence of sentience (or pick any
>>>other undefined phenomenon) in a given embryo/fetus, I argue we
>>>have at least something to consider.
>
>> I think the analogy to a comatose patient has a weakness here. With a
>> comatose patient, we have someone we who *was* a functioning person,
>> complete with whatever we choose to describe as intelligence. In the
>> fetus, we have a being that has never yet displayed this same
>> functionality. 
>
>Granted.  The analogy has a weakness.  I'll need some convincing that
>it's a significant one.
>
Since we seem to have agreed that "personhood" per se is of limited
use in this discussion, I don't think it's worth the time or bandwidth
needed for us to mutually rip our interpretations of this analogy to
shreds, do you?

>>>> The reson I insist on proof of
>>>> presense, not the absense, is simple. Lack of proof in favor of
>>>> existance can be considered to resonably show nonexistance.
>
>>>True, it *can* be considered as such.  But should it?  Jeffrey James
>>>Price just got a taste of the consequences of a similar (but admittedly
>>>not equivalent) assertion.  (Check it out.  I predicted that he would
>>>see a truckload of examples of the consequences of his idiotic
>>>reasoning.  My favorite: "There are exactly 223 chemical elements.")
>
>> I missed this, sounds like it was a real fun flamewar. :)
>
>Pretty one-sided, actually.  His contention (paraphrased with
>amazing accuracy): you can't prove it (z/e/f personhood) false,
>therefore it's true.  Fun it was.
>
I tend to take the opposite (and less absolute view) that if you can't
prove it exists, then it is safe to assume that it does not. While
there are plenty of examples of cases where this turned out to be
false, it can be defended as making judgements based on the best
available information. 

>>>Condider: there is no evidence for the existence of any sort of
>>>logical intelligence on the part of Mr. Price.  This, however,
>>>does not "reasonably show" the nonexistence of intelligence.  It's
>>>quite possible (perhaps likely) that the individual possesses
>>>intelligence but chooses not to exercise it.
>
>> While the humor is appreciated, I think we have to admit that the
>> ability to post to Usenet does show at least minimal intelligence. The
>> intelligence may be severely flawed, and even irrational, but it's
>> still (minimal) intelligence. :)
>
>I said "logical intelligence".  Whatever that is, their ain't no
>evidence that it's there.  I have witnesses.
>
Having read a couple of his posts after responding to yours, I'm going
to have to completely concede this issue. I couldn't find any evidence
either.

>>>As a scientist, I can say that one of the scourges of science is
>>>"negative data": I looked and couldn't find X.  Therefore it's not
>>>there.  In fact, such data is considered insufficient (by many I've
>>>spoken with) for the awarding of a Ph.D.
>
>> I'm going to speculate that this is because the aim of a PhD candidate
>> is to contribute something original to the science, not merely deny
>> the existance of something.
>
>Well, no, that's not really correct.  If one were able to "deny the
>existence of something" and the proof had any significance at all,
>it would be a contribution worthy of a Ph.D.  
I thought I said that... Maybe I didn't make myself clear, but in
this, we are in agreement.

>My point was that
>looking for something and failing to find it is *NOT* tantamount
>to disproving its existence.  People looked at nervous tissue
>through microscopes for generations, and couldn't see synapses.
>Some concluded that they didn't exist, and their "reticular
>theory" of the structure of the nervous system survived till the
>50's, when Palay and Palade took the first electron micrographs
>of synapses.  I think there's a lesson there.
>
I think I understand your point. The problem I see is that we aren't
*just* discussing theory. If we were, there would be no controversy. I
am not about to claim that the information we have is 100% accurate.
I'm not that fond of being flamed. :)
But we do have to make decisions. Despite the uncertainty of our
theoretical knowledge, there are real women with real pregnancies
trying to figure out what to do about them. I'll admit that we are
destroying a fetus of unknown potential. (It's just as likely to grow
up to be a serial axe murderer as it is to find a cure for the common
cold, though.)
So what do we do?
I don't think there is going to be a good answer, not for everybody.
That's my main reason for advocating leaving the choice to the
pregnant woman. I don't think the potential of the fetus can outweigh
the reality of the woman.

On another note... Have you ever noticed the tendancy of researchers
and authors of medical texts to work with others with similar names?
Examples: Palay and Palade, Waley and Wong, Potter and Perry, Hill and
Howlett...

BTW Steve, you forgot to include a gratuitous insult... Are you
slipping up? ;)

--
                  Mark Cochran          merlin@eddie.ee.vt.edu
These are the views of my employer, your employer, your government, the
Church of your choice, and the Ghost of Elvis. So there.
Member, T.S.A.K.C.
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