Date: Thu 22 May 2003 - 20:48:15 GMT
> on 5/19/03 1:26 PM, Keith Henson at email@example.com wrote:
> > Do you have any doubt that the physical representation of a meme in
> > a brain (where memes exist as a class of memory) can be found?
> > (Given fine enough tools of course.) Here is a thought experiment
> > on how to do it:
> > Take a snapshot of the places and states of every atom in a
> > brain. Immediately have the brain learn a new a new phone number,
> > snapshot again. Subtract. Ignoring the (eventually solvable)
> > engineering problems, what is left is the physical representation of
> > the encoded phone number or meme or whatever. Might be hard to
> > figure out how it is encoded, but that's just detail.
> I don't doubt that physical changes happen in the brain as a result of
> learning this that and the other thing. That's not an issue. But
> there is no good reason to regard any of those changes as evidence for
> In any event, you have more faith in our engineering capacity than I
> do. I haven't got the faintest idea whether or not we'll ever be able
> to do what you propose. But, assuming we can do that, there's another
> problem with your thought experiment. As others have said, the brain
> is a very fluid world, cells are always dying, etc. So, when we get
> your difference image, not only does that difference image reflect the
> results of learning the phone number, but it reflects other things as
> well. And we have no way to sort those things out.
> But let's assume we can solve that problem as well, for the sake of
> your thought experiment. Let's go through that procedure with Jack.
> Now we snapshot Jill's brain and Jack gives her a sheet of paper with
> the phone number on it and asks her to memorize it. When she's done
> that we snapshot her brain and make the difference image.
> Let's compare the difference image for the two brains. We have no
> particularly good reason be believe that they will be very much like
> one another. What is even worse, we don't even have any principled
> way to make a comparison. One of the interesting characteristics of
> the nervous systems of small invertebrates, like C. elegans (and, I
> suspect, your slug) is that each phenotype has the same numbers of
> neurons in the same arrangement. Thus each individual nematode (C.
> elegans) has 302 neurons in its nervous system, no more, no less. This
> means that it is easy to put the neurons in one nematode into 1-to-1
> correspondence with the neurons in another.
> But vertebrate nervous systems are not like that. We have many more
> neurons and we have no reason whatever to believe that one person has
> the same number of neurons as another. Given the range of sizes from
> one brain to another it is obvious that different brains have
> different numbers of neurons. So we can identify some neuron in
> Jack's brain but there is no way, not even in principle, to identify
> the corresponding neuron in Jill's brain. And if we can't establish a
> 1-to-1 mapping between neurons, we can't do it for synapses either.
> So how can compare the difference images to see if the meme has
> "replicated" from one brain to the other?
> With that in mind, let's add a step to our experiment. When we've
> made our "before" image of Jill's brain we're going to use our
> "before" and "after" images of Jack's brain to predict the "after"
> image of Jill's brain. If we really understand how the encoding
> works, and if replication really is involved, then we should be able
> to come up with a pretty good prediction of what Jill's "after" image
> will be like.
> But how could we make a prediction? If we don't know what neurons in
> Jill's brain correspond to the neuron's in Jack's, then how can we
> make a prediction? It's quite meaningless.
As has been said here by me before, the encoding of the selfsame meme in differing cognitive gestalts will be similar but not identical, since it must accommodate to and be assimilated by the differing gestalt already present. This does not mean that the same meme ain't in both minds, just that it is incoded slightly differently for each. Most likely, though, the respective brain regions will be the same (such as the occipital lobe for visual memories, the temporal lobe for auditory memories, etc., and these and the association cortex for language coded memes, association + temporal for spoken memes; association and occipital for written, with some bleed-over into the temporal, since we tend to talk the text to ourselves as we read, but not vice-versa, since we do not typically visualize a textual representation of spoken discourse, although, if we try, we can).
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