On Tue, Oct 18, 2011 at 1:01 PM, Craig Weinberg <whatsons...@gmail.com> wrote:
>> The speech centres must, through a relay of neurons, receive >> information from the visual centres if the subject is to make any >> statement about what he sees. > > What makes you think that's the case? That's a blatant fallacy, isn't > it? "The windshield wipers must, through a relay of mechanical parts, > receive music from the from the radio station" > > Visual centers don't talk, and speech centers don't see. People see > and talk. When you speak about what you see the information carried in the light that comes into your pupils must somehow get to the motor neurons controlling your vocal cords. How do you think this happens? >> If the visual centres are artificial, >> but producing the same neural outputs to the rest of the brain, > > They probably won't though. They can't because they don't feel the > appropriate qualia to repspond to events in the same way over time. It > depends how close they are to natural neurons, maybe even the neurons > which are genetically specific to that individual. > >> then >> the rest of the brain will respond as if vision is normal: > > If there is some part of the natural visual centers there, they may > very well be able to use the artificial ones as a substitute - like a > cane, but you can't use a cane as a substitute for your whole arm. > >> the subject >> will say everything looks normal, he will grasp things normally with >> his hands, he will paint or write poetry about what he sees normally. >> His motor cortex cannot be aware that the visual cortex has changed, >> since the only awareness of the outside world the motor cortex can >> have must come through the surrounding tissue. > > I understand how you are thinking about it, but I think that would > make sense if there were a such thing as functional equivalence of > qualia, but qualia has no function. There is no way to know if you can > make something that feels just like a neuron unless it is in fact a > natural neuron. > >> >> > Since we know absolutely that we have experiences which cannot be >> > observed directly in the tissue of the brain, there is no sense in >> > imagining that replicating what we observe in the brain will not be >> > missing crucial capacities which we can't anticipate. Even replacing >> > simpler organs with actual human organs have a risk of rejection. Why >> > would the brain, which is presumably infinitely more sensitive than a >> > kidney, have no problem with a completely theoretical and unrealizably >> > futuristic artificial device? >> >> We assume that the artificial device reproduces the pattern of neural >> firing and nothing else. Do you think that is *impossible*? Why? > > Sure, it might be impossible. Because the pattern is context > dependent. If you have a bunch of separate heart cells, they will all > beat regularly but not synchronized. So you make an artificial heart > cell that beats regularly at the same interval as any of the other > heart cells. When you put all of the separate heart cells in a dish > together, they all will synchronize - except the artificial ones. If > you were to put enough artificial heart cells in a living heart, you > would cause an arrhythmia and kill the person who is using that heart > to live. Cadrdiac myocytes in culture can synchronise their beating through direct contact. Artificial myocytes, if they were to replicate this behaviour, would have to be sensitive to the action potential of the natural myocytes. In general, any observable behaviour of the biological system that you want to replicate can be replicated by some technology. Qualia are not observable and it is an open question whether they can be replicated, so we assume that they can't and consider the consequences. The consequences are that a person's qualia might change but, because the inputs to the motor neurons controlling speech are the same, he would declare that nothing has changed. > Neurons are orders of magnitude more interconnected than that. The > idea that there is a fixed 'pattern of neural firing' which can be > derived from a single neuron in isolation that can be extrapolated out > to the brain as a whole is just factually incorrect. It's not some > exotic wackiness that I dreamed up, it's actually not at all the way > that the brain, or any living organism works. Neurons aren't just > miniature brains, and brains aren't just a pile of neurons. It's like > assuming that if you make a mannequin that acts like a nomadic hunter > gatherer, you should have no trouble repopulating New York, London, > and Hong Kong with a large group of them. I keep repeating that there is no "pattern of neural firing" to replicate. Whether a biological neuron fires or not depends on its present state and its inputs. A neuron that would fire if the temperature is 37 degrees and the extracellular potassium concentration is 5 mM might not fire if the temperature is 39 degrees and the potassium concentration 6 mM. The model of the neuron has to incorporate knowledge about how the neuron is affected by these variables, and this knowledge is obtained through research. But the model cannot predict what the temperature or the potassium concentration is going to be at a particular time, since neither can the biological neuron. -- Stathis Papaioannou -- You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to firstname.lastname@example.org. To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/everything-list?hl=en.