X-Message-Number: 26034 Date: Sat, 16 Apr 2005 09:20:46 -0400 From: Thomas Donaldson <> Subject: Once more for Yvan For Yvan: It would be nice if you would listen. All the theorems etc which you invoke do not normally deal with the problem of TIME. Turing did not deal with the problem of time. Computers weren't originally invented to deal with the problem of time (in their work, not in physics equations they might be used to solve). This remains a factor in their design. And certainly even with the fast sequential computers we have now, they work quite well to solve problems with do not require solution within the next nanosecond. And if they work fast enough on ordinary jobs, time sharing remains quite useful. Brains and nervous systems, however, did not evolve in a quiet world in which they had plenty of time to solve the problems they were presented with. They had to solve those problems fast or they would turn into nutriment for some faster animal. Time sharing neurons simply weren't an option --- except possibly for some animals now long extinct and hardly noticed. This is why our brains operate not only as parallel computers, but (as is usually not done with even our parallel computers) with all those neurons working in parallel on different but related jobs. The world is full of simultaneous events, and we could not deal with them otherwise. You may argue, with a bit of reason, that if the processors involved are much faster than neurons then time sharing once more becomes an option. The problem is that simultaneous means SIMULTANEOUS. PERHAPS a computer using time-sharing might be fast enough to deal with some simultaneous events, but sooner or later it will not deal with all. As a simple example, it may be faced with a need to physically balance itself for an instant. If its limbs and muscles don't work simultaneously it falls over and will eventually be consumed (perhaps by other better designed devices). If the balance test is hard, then even a few nanoseconds delay leads to falling. Second, you claim that growth is quite possible IN SOFTWARE. This statement verges on the ridiculous. Yes, you can simulate growth in software. Yet suppose that the growth of new synapses and even new neurons, in our dentate gyrus and elsewhere, turns out to be essential for long term memory. (Many but not all neuroscientists think that). Exactly how does your computer version of a brain do that growth in software if it needs new neurons even to remember long term? The brain changes required are changes in the physical anatomy of the brain. If you ran out of fuel in your car, and told me that you could solve this problem with software in your car's computer, I would suspect you of insanity. As for your reading in neuroscience, please say just what books and articles you've read. The book by Byrne and Roberts is good (FROM MOLECULES TO NETWORKS) but hardly more than a start. I am glad that you've at least read some biochemistry. Best wishes and long long life for all, Thomas Donaldson Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=26034