From: sfm@manduca.neurobio.arizona.edu (Stephen Matheson)
Newsgroups: talk.abortion
Subject: Re: Spoken Like a True ProLifer
Date: 9 Jan 93 00:51:34 GMT
Organization: University of Arizona UNIX Users Group

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.

> (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.

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.

>>> 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.

>>> 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.

>>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.

>>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.  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.

[deletia]

--

Steve Matheson   Program in Neuroscience   University of Arizona
sfm@neurobio.arizona.edu