On Aug 13, 8:00 pm, Stathis Papaioannou <stath...@gmail.com> wrote:

> The artificial device must replicate all the I/O behaviour of the
> original neurons at the interface with the rest of the brain. This is
> purely a problem for engineers who neither know nor care about qualia.

What I and others are pointing out is that how you define 'I/O
behavior' is the determining factor of the thought experiment. For
example (from http://themedicalbiochemistrypage.org/nerves.html):

"Acetylcholine (ACh) is a simple molecule synthesized from choline and
acetyl-CoA through the action of choline acetyltransferase. Neurons
that synthesize and release ACh are termed cholinergic neurons. When
an action potential reaches the terminal button of a presynaptic
neuron a voltage-gated calcium channel is opened. The influx of
calcium ions, Ca2+, stimulates the exocytosis of presynaptic vesicles
containing ACh, which is thereby released into the synaptic cleft.
Once released, ACh must be removed rapidly in order to allow
repolarization to take place; this step, hydrolysis, is carried out by
the enzyme, acetylcholinesterase. The acetylcholinesterase found at
nerve endings is anchored to the plasma membrane through a
glycolipid."

So, in order to replicate the I/O behavior of a single axon of a
neuron that traffics in ACh, are you talking about engineering a
nanotech factory which eats the right amount of choline (if not, you'd
have an excess of choline building up in the replaced areas of the
brain), and produces genuine ACh? Are you talking about having an
artificial glycolipid holding a supply of acetylcholinesterase to
accomplish hydrolysis to enable repolarization like the other neurons
of that type? You can't simulate the production of those substances
electronically or produce them inorganically, so any replacement
system would be based on organic chemistry. If you were able to
accomplish the production of those substances as well as conduct
electric signals properly, that still only scratches the surface of
the physiological issues. From 
http://www.mind.ilstu.edu/curriculum/neurons_intro/neurons_intro.php
:

"While we are considering numbers, it is worth noting that there are
as many as 50 times more glia than neurons in our CNS! Glia (or glial
cells) are the cells that provide support to the neurons. In much the
same way that the foundation, framework, walls, and roof of a house
prove the structure through which run various electric, cable, and
telephone lines, along with various pipes for water and waste, not
only do glia provide the structural framework that allows networks of
neurons to remain connected, they also attend to the brain's various
house keeping functions (such as removing debris after neuronal
death). "

If your replacement neurons don't die, then you're changing the
relationship of them to 98% of the cells in the brain and the I/O is
different to the ecosystem overall. If you could manage to engineer a
replacement component which satisfies all of those electrical,
biological, and chemical roles, but still somehow manages to be, in
some significant way 'not a living cell' then there is still the
matter of whether or not the cell body itself is the thing that
actually experiences the various inputs and determines the outputs
according to uncomputable awareness-based algorithms or whether
experience somehow arises metaphysically through the aggregate of
unexperienced mechanical I/Os which can be replicated
deterministically.

If the former case is true, the replacement cell body may not be able
to produce the organic sense required to modulate the functions of the
cell in it's native improvisational mode so that it will neither fool
surrounding tissues nor perform the critical experiential function in
between inputs and outputs which would form the meat of perception and
awareness. If the latter case is true, there is no way to tell whether
the metaphysical requirements form instantiating high level awareness
could be satisfied by the design of the replacement. The exact
mechanism by which dumb I/Os are translated into nonphysical emergent
properties would have to be fully understood in order to accomplish
substitution by engineering.

Craig

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