From: mcochran@nyx.cs.du.edu (Mark A. Cochran)
Subject: Re: Spoken Like a True ProLifer
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Date: Tue, 12 Jan 93 04:00:01 GMT

In article <1993Jan11.065635.16749@organpipe.uug.arizona.edu> sfm@manduca.neurobio.arizona.edu (Stephen Matheson) writes:
>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):

[Deletions...]

>>>> 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.
>
Redundancy does not help if the signal is *lost*, although it would
help if *multiple* signals were being sent, and only *some* were being
lost. Does your study or neurology indicate tha tthe brain sends out
multiple copies of each signal? I admit I don't know one way or the
other.

>>>> (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.
>
Which large segments function "quite nicely" without myelin? The only
demyelinating disease process I've had experience with is
Guillain-Barre' syndrome (acute ideopathic polyneuritis). In this
case, weakness is followed by paralysis as the disease progresses.
The classic disease affects the ventral roots of the spinal cord,
although the Guillain-Barre'-Strohl variant does affect the dorsal
roots (and causes loss of sensation instead of loss of muscle
response). The demyelination of the roots causes a loss of function,
up to the point at which respiration stops, and the patient is trached
and ventilated mechanically. Function is lost until the myelon
sheathes regrow. Further, we know that in early pregnancy, these same
roots must be myelinated before movement (other then twitches, which
occur as much from random excitability of the muscle tissue as
anything) takes  place i nthe fetus. Considering this, and considering
how much more complex the electrical activity of thought must be, do
you not think it is resonable to say that thought is unlikely to be
present?

>>>> 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.
>
I personally wish that Dr Sagan would stick to astronomy, or whatever
it is he's trained in...

>[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?
>
To my own satisfaction, yes. But if "personhood" is based almost
wholey on subjective data and personal philosophy, isn't
"conciousness" as well?
If we define conciousness as the ability to respond intentionally to
oputside stimulation, then I think we can show it's existance. The
"intentionally" qualifier rules out the reflex motions o a fetus is
capable of, but also puts neonates on shakey ground.

>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.
>
Of course he's not, or I couldn't speak for his ghost. ;-)
The mass of tissue in a 6 week embryo (not fetus, not until week 9, as
you pointed out to another poster... ) which may eventually become a
brain may well be firing impulses. But does it qualify as "mental
function" (which I take to mean some relation (cousin, perhaps) to
intelligence)? Motor neurons fire at random, even in adults (you've
seen peopel twitch), so it can be assumed (or proven, possibly) that
others do as well. But for it to qualify as some omen of developing
intelligence, it would need to be (to me anyway) organized. 
I don't put much faith in the EEG, honestly. I've a friend in the
neurophysiology area who has been known to say "I can get an EEG of 3
cells in a petri dish." It's a far cry from the brainwaves seen in
adults, or even neonates, but it is an EEG...

>[More stuff about Mr. Price deleted.  Poor guy.]
>
Indeed. Maybe he shuld have a telethon?

>>>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.
>
More then somewhat, on both sides, unfortunately. Too much "moral
absolutism", perhaps?

>> 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.
>
Certanly true. I used the other examples because those are the ones
usually drug through the mud here.

>> 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.
>
I don't think this is what you mean, but your first line above makes
it sound as if the woman approaching the abortion provider has not
already decided what she wants. In cases I've seen, the woman has
approached her OB, or GP, who either performs the abortion or refers
her to a suitable provider (especially in late term or other high risk
cases). The only cases I know of in which a physician has encouraged a
woman to abort has been cases of severe abnormality. And even in these
cases, the choice always lies with the woman.
I can agree with you on the different realities idea.
We both see pre-birth "personhood" as a possiblity. I think the main
point of difference we have is that you choose to make any error (wrt
this possibility) in favor of the fetus (subject to the balancing you
mention above), while I prefer to make that possible error on the side
of the woman carrying the fetus.

>> 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...
>
I also left off Abrams and Adams. :)

>> 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...
>
HA! You admit you don't have the dictionary memorized? What sort of
t.a poster are you? Did your last EEG get reverse polarization and fry
that miserable excuse for a brain of yours??

--
                  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.
Newsgroups: talk.abortion