On Aug 13, 8:00 pm, Stathis Papaioannou <[email protected]> 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 -- You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/everything-list?hl=en.
