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machine brains

Joe Kilner jjmk2 at hermes.cam.ac.uk
Wed Feb 17 13:22:15 EST 1999


>>> What do we wish to simulate and at what level? Are we talking, for
>instance,
>>> of the brain of rat? This is a mammalian brain, it has all the parts of
a
>>> man's brain, just not so many neurons? What is the unit of our
>simulation?
>>> The neuron?
>>>
>>> The neuron is a large assortment of neurons, I have no idea how many. I
>>> would be happy if someone would give me a guess or a citation as to how
>many
>>> in an average neuron. Some would say that until we know the story of
>every
>>> molecule we cannot simulate a neuron. This is hogwash.
>>
>>We can simulate a neuron, but we need to know more about how neurons
>>interconnect. At one time we thought all neronal connections were
>>axon-to-dendrite. Then we found axon-axonal, electrical, even
>dendrite-dendrite
>>connections. Without an understanding of all those mechanisms we can't
>>completely model a single neuron.
>
>Yes! And you can add ephaptic and hormonal effects. I say we must work with
>what we have. If you insist on the life history of every molecule you are a
>latter day Luddite.
>

I think the point being made here was that we don't know what is salient and
what is simply coincidental.  If you dismiss the inner workings of neurons
you may well be throwing out a particularly important baby with the
bathwater.

>>Moving up to small networks, it's only recently that the role of nitrous
>oxide
>>has been revelealed as a diffuse, local neurotransmitter; unless you model
>that
>>as well, you don't have a full model of the physical level of the brain.
>And
>>there's no doubt more to be discovered.
>
>
>These are all just excuses for a return to contemplation of our beautiful
>thoughts, our marvelous soul (mind).
>

You have a habit of redefining the words people use to suit your arguments!
When people say you can't explain thought without mind you say that thought
is a purely mechanical process, while here you are implying that thought is
a property of the mind.  The meaning of words is particulalry important in
science - an electron means an electron and nothing else - and neuroscience
should be no different.  If you want to speak of two different types of
thought then give (or use) two different names to them otherwise all you do
is confuse.


>>There's a danger here in defining the question down to the point where
it's
>>simple, but uninteresting. Supposing you assemble 200 million of your
>synthetic
>>neurons into a mass and start generating S-R pairs. Do you have a mind, or
>just
>>an interesting programable array?
>
>
>You misunderstand me. First we are to understand how the brain works, then
>we are to speak of designing a thinking machine (if we wish). Note that we
>talk only of design, no one should be so foolish as to think of actually
>implementing such a machine.
>

I think the point being made here is that you might _want_ to model the
brain, but how do you know that you have done it?  What are your success
criteria?  A machine that appears to exhibit a mind?  Something you can talk
to?  And why would no one want to implement it?

>>> The endless molecular activity of a synapse can be lumped
>>> together with a few parameters. The synapse is strengthened or it is
>>> weakened. The synapse disappears. there is axonal growth and new
synapses
>>> appear. All these are subject to a time dependence (from birth to death
>of
>>> the organism). A synaptic event involves a local change in the potential
>>> difference between the interior and the exterior.
>>>
>>> This is not very much as simulation goes.
>>
>>It's an incomplete picture. There's a lot more going on than simple
>>axonal/dedritic transmission.
>
>
>Lord, yes! But not so much as to justify a throwing up of hands and a
>retreat to religion.
>

I've not heard anyone else here retreat to religion!  Every time someone
mentions mind or soul in a non-dualist sense you dismiss this and say that
mind/soul (your equality) is a matter for religion.  Just saying that we
don't know enough at the moment to explain the mind scientifically does not
mean we never will!

>>> There is no problem as long as we keep the soul (mind) out of it.
>>
>>Hmm. I think I'd argue this point. What are we trying, in the end, to
>explain?
>>Mind. If our brain model doesn't actually make a stab at explaining mind,
>what
>>good is it? It's just another hypothetical model of nothing in particular,
>like
>>so many other AI models.
>
>
>Artificial Intelligence has nothing to do with the brain. AI is concerned
>with the mechanization of the manipulative algebra of the sentential
>calculus.
>

Ooooohhhhh.... long words....... ;)  As far as I'm concerned it's just
another lecture course....

>Explanations of the soul (mind) belong to religion. I say that theology
>should be put to one side until the brain is explained. When this is done
>one may turn to religion and talk about the soul (mind).
>

Why do you keep on relegating questions of the mind to religion?  Just
because the most prevalent theory happens to mean that the mind can't fit
into scientific thinking doesn't mean that you should always dismiss any
theories that _do_ allow the mind to be a scientific object  Untill you have
a decent reason to dismiss such theories then could you at least accept the
possibility that mind may be an area reachable by rational thought.  I would
like to think about the mind and how it interacts with / is part of the
brain without feeling that I am turning into a religious nut.

>>> The brain
>>> is simple and its activities are simple. We are overwhelmed by the
number
>of
>>> neurons, by the number of nuclei, by the number of tracts, but if we
lump
>>> the trees together we shall see the forest.
>>
>>Of course, I think the forest is Mind.
>
>
>Good enough! But save it until we get the brain explained.
>

I think what we need here is a language we can all agree on.  It is, I
think, quite clear that we are talking about different "brains" "minds" and
"souls" to eachother, and I think that is where most of the argument /
misunderstanding stems from.  Within Ray's view of the soul / mind  then his
arguments make perfect sense but if you have a different view of the soul
and a different view of the mind (as I do) then his arguments no longer hold
much ground and quickly become self refferential (and of course vice versa -
I would not dream of claiming that my arguments have any kind of God given
validity!)

So what we need to have are several words for mind / soul / brain / thought
so that we can all know what we are infact talking about!  Rather than
complicating matters I think you will find it suddenly makes all our
arguments go away as we discover that we are talking about totally different
things.  From this point we can then try to see which system fits our
observed real world best and from that draw conclusions about the progress /
non-progress of a scientific understanding of the brain with or without the
mind.


        Joe

--  Churchill College Cambridge  --
--  http://choo.chu.cam.ac.uk/  --







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