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- Path: sparky!uunet!usc!cs.utexas.edu!asuvax!ncar!noao!amethyst!organpipe.uug.arizona.edu!news
- From: sfm@manduca.neurobio.arizona.edu (Stephen Matheson)
- Newsgroups: talk.abortion
- Subject: Re: Spoken Like a True ProLifer
- Message-ID: <1993Jan11.065635.16749@organpipe.uug.arizona.edu>
- Date: 11 Jan 93 06:56:35 GMT
- References: <1993Jan10.151453.22562@mnemosyne.cs.du.edu>
- Sender: news@organpipe.uug.arizona.edu
- Organization: University of Arizona UNIX Users Group
- Lines: 185
-
- From article <1993Jan10.151453.22562@mnemosyne.cs.du.edu>,
- by mcochran@nyx.cs.du.edu (Mark A. Cochran):
- > 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
-
-
- [Sigh. Deletia.]
-
- >>> 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?
-
- I suppose if we built in enough redundancy, we might be able to pull
- it off.
-
- >>> (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. :)
-
- Well, large segments of the nervous system function quite nicely
- in the absence of myelin, suggesting that the failure rate is
- not a big issue. Your point that "thought processes" might require
- higher standards for fidelity than, say, the sympathetic nervous
- system is well-taken but little more than an assumption. The
- possibility that fetal mentation is present, but quantitatively
- different from that of adult humans, remains and is, IMO, not
- insignificant.
-
- >>> 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...
-
- You don't need to. It's been cited at least once on t.a in support
- of the must-have-cortex-and-synapses-and-brainwaves-to-think-and-
- therefore-to-be-a-person theory of personhood.
-
- [Large deletion]
-
- >>>>> 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.
-
- Can you prove that consciousness exists?
-
- On a different tack, if I show that the developing brain of a
- 6-week-old fetus is busily firing impulses (long before "brainwaves"
- can be detected by an EEG), then I can make a case for the
- POSSIBILITY of mental function. Of course, I can't prove it
- exists, but this makes the situation quite different than, say,
- the contention that Elvis is alive on Mars.
-
- [More stuff about Mr. Price deleted. Poor guy.]
-
- >>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. :)
-
- Your caution is well-advised, and, in my experience, somewhat rare.
-
- > 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.)
-
- It's more than likely going to grow up to be a rather average
- individual whose value is, IMO, equal to the 2 examples above.
-
- > 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.
-
- I am resigned to the reality of choice being left to women and
- abortion providers. That's why I think it's worthwhile to
- discuss the moral issue of abortion (in this case by discussing
- scientific aspects of the personhood question). While I agree
- that the fetus mustn't outweigh the mother, I reject the notion
- that the conflict is between "potential" and "reality" and assert
- instead that it is between 2 different realities.
-
- > 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...
-
- You left out Hodgkin and Huxley just to irk me, didn't you?! :-)
- Well, you said you're not into neuro, so...
-
- > BTW Steve, you forgot to include a gratuitous insult... Are you
- > slipping up? ;)
-
- Slipping up? No. Cracking up? Why yes, you pathetic pile
- of primordial soup. Was that gratuitous? I'd better look it
- up...
-
-
- --
-
- Steve Matheson Program in Neuroscience University of Arizona
- sfm@neurobio.arizona.edu
-