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machine brains

Jerry Hull ZZZghull at stny.lrun.com
Tue Feb 16 17:06:33 EST 1999


On Tue, 16 Feb 1999 13:59:11 -0500, Michael Edelman <mje at mich.com> wrote:

>
>
>Ray Scanlon wrote:
>
>> 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.
>
>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.
>
>> What we simulate is what interests us. We are interested in the neuron as an
>> electromechanical device that influences other neurons. The myriad of
>> molecular activities that have to do with the maintenance of a living cell
>> are not involved.
>
>Ah, but they are. Axonal transport regulates the rate at which an axon can
>produce vesicles of transmitter. Availability of calcium can regulate firing
>activity. All these can be influenced by metabolism, mitochondrial activity and
>so on. The cell wall is pivotal in transmission of an AP to an axon. We need at
>least a functional understanding of the relationships.
>
>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?

This stuff is pretty interesting.  Can you recommend a good not-too-technical
read on the current state of scientific understanding VAV neurons & the
interesting things that can be built from them?

--
Jer
"However far you may travel in this world, you will still occupy 
the same volume of space".  Traditional Ur-Bororo saying.



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