X-Message-Number: 3333
From:   (Nancy Lebovitz)
Newsgroups: sci.cryonics,sci.life-extension
Subject: Re: Brain backup proposal
Date: 22 Oct 1994 06:58:32 GMT
Message-ID: <38ad6o$>
References: <389uk6$>

In article <389uk6$>,
Keith F. Lynch <> wrote:
>I'm assuming that a person's personality, memories, aspirations, and
>identity (self-circuit, in Robert Ettinger's words) are completely (or
>at least, sufficently) defined by their neural connectivity diagram.
>This diagram would consist entirely of information on what the odds
>are of each neuron firing, given the current state (firing vs. not
>firing) of all the adjacent neurons, and given the current levels of
>each neurotransmitter chemical in the brain.  If this assumption is
>wrong, my backup method won't work.  (Does anyone have any good evidence
>for or against it?)
I don't have evidence, but I'd bet on general principles that neuro-
transmitters aren't evenly distributed.

(The general principle is that *nothing* is evenly distributed--I
was insufferably smug when I found out that cosmic rays didn't come
in perfectly evenly.)

>The subject would be injected with about 10^12 nanoprobes.  Each probe
>would circulate in the bloodstream until it found itself touching a
>neuron.  Then, it would attach itself to the neuron.  It would emit a
>chemical signal whenever the neuron fires.  That's all it does.
Do you have any ideas about how it would recognize neurons? How
different are brain cells from other nerve cells? Or is that
the kind of question that will have to wait for the level
of technology that will make the probes possible? 

>A tiny proportion of these probes would emit a chemical signal which
>reports the current levels of various neurotransmitters.  (I'm assuming
>that the level of every neurotransmitter is roughly the same across the
>whole brain at any given time.  Does anyone know if this is true?)

Even if I'm right about n-t's not being evenly distributed, there
might be a way around it....especially if something is known about
what parts of the brain tend to accumulate which n-t's. Since the chemical
signal that reports the neurotranmitters will be time-stamped,
it may be possible to reconstruct which regions have which
n-t's at a given moment. 

This is much more likely if the signals record all the n-t's at
a given spot (as you imply) rather than just one n-t/signal. With
luck, there might be chemical cues indicating what part of the
brain the probe was in which could be included in the signal.

All this might mean that you'd need a higher proportion of n-t

If it turns out that n-t levels very importantly every few
cells (which I don't consider likely), I'm not sure what the
solution is.

Do you have any idea about how big the probes will need to
be? I'm at least as concerned about that as I am about the
safety of the chemical signals. 
>So long as the recreated brain (whether it's made of flesh, silicon, or
>something else, and whether there is some particular piece of matter
>which acts as each neuron, or whether it's emulated in software) has
>the same statistics as the original, its behavior should be the same
>as the original subject's.  And given that its behavior is the same,
>I believe its internal subjective experience would be the same.

I suspect that if the brain is simulated in a very different sort
of body, its experience will soon also be very different from what
it was in its previous body. This might or might not be desirable.

Also, I wonder about developing new ideas....is a record of how
my brain operated when I thought something new enough to offer
the same sort of creativity later? 

What about new skills? I can't juggle now, but I could presumably
learn. Would a record of my current non-juggling self be able
to learn? Maybe people recreated from records would have to have
expansion modules. 

If I'm not mistaken, people (past a very young age) don't grow
new brain cells, but do grow new dendrites--a really good simulation
might need to include the person's pattern for growing new dendrites.

On the other hand, a good record of a year plus a generic dendrite-
growing capacity might be enough.

I wonder if we have a philosophical/tempermental difference here.
I get the impression that you think that the current you is enough
to be a satisfying simulation, whereas I'm concerned to have the
same sort of future selves that I would otherwise have. 

>It's not clear to me whether, if a memory isn't recalled for a period,
>that means that certain related neurons won't fire for that period.
>If this is the case, that means that anything the subject doesn't think
>of during the backup won't be picked up, and the restored subject will
>have no recollection of them later.  That possibility is the main reason
>I suggested a backup time of one year.  I'd much rather have *all* my
>memories, but I can live without the ones I don't think of for a year,
>if the only alternative is having no backup.  If I were making a backup,
>I'd be sure to go over my old photo albums, my old usenet files, visit
>places I used to live, and reminisce with old friends.

It's an interesting question--my personal bet is that the memories
are all there in the brain all the time, and that the ones that
aren't in consciousness are just firing less often, which translates
as less vividness. 

If this technology turns out to be workable, I wonder if parents will
start having their children's brain patterns recorded at birth (or
earlier?) so as to have a complete record.

>There are other issues.  For instance, where do the sensory and motor
>nerves hook up?  I'm hoping this would be clear from internal context,
>together with a more advanced knowledge of how brains are typically
>wired.  It should, for instance, be simple enough to not only locate the
>visual cortex, but to reproduce any image that was seen by the subject
>during the backup.  Analogously with the other senses.

This raises some interesting privacy issues. 
That was a very interesting essay--I hope that my comments are of
some use.

Nancy Lebovitz

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