X-Message-Number: 26096 From: Date: Wed, 27 Apr 2005 02:39:51 EDT Subject: Uploading (3.ii.1) First bits. Uploading (3.ii.1) First bits. There is a first attempt to define the rough needs in term of bits allocation inside an artificial neuron. The action potential is a simple rectangular signal, it needs only one bit. The presynaptic vesicle release needs at most 9 bits, these split into: 7 for one site and 2 for up to 4 sites. The probability P must rule a seven levels system, if it has far more than 7 levels itself, there is a waste of information, so P must have 3 bits. The post synaptic dendrite spine head may have up to some hundreds receptors of a given kind and may be 3 or 4 kind. It seems that 10024 levels would fit nearly all needs. That define a 10 bits signal. The dendrite head, for a given neuron kind, may be defined by 4 receptor species, each with 256 possibilities, from 0 receptor to 255. This would take 8 bits and for 4 species: 32 bits. This give 4 billions possibilities for a spine, hardly a standardization. In fact, we may be unable to count the receptor number in a given spine head after some hours of ischemic decay. If we stardardize the number with 16 level or 4 bits, that would say that we count the receptor number as 0 to 7 with code size 0000, 8 to 15 with code 0001, and so on up to between 248 and 255 receptors in code 1111. There would be 16 bits used for the spine size or 16,000 possibilities. The next element is a dendrite section with Green's function differential solution. There may be from zero to 20 amplifier spines. the number and position matter here, this give one million of possible solution. More: One spine may have different gate levels from another for different signal intensity, because of different channels types. So we can't assume a single probability table for all spines. Depending on the trafic density for excitatory or inhibitory signals, the probability table can be shifted to another. At synaptic level, 16,000 spine heads possibilities have been assumed, this translate here into 16,000 different probability tables. The probability curve is defined by a number of point. Each channel block define one such point. There was 16 blocks at most for one channel species and 4 species. This give 64 possibilities to adjust the probability curve. Each table has so 64 element. At a given potential intensity, it would be useless to have a probability defined on more bits than the gap to the next channel number. Because the block here have 8 channels, this may be expressed with 3 bits. To take into account the Shannon's theorem on digitized signal, we may use x2 more states or 16. A probability would then be expressed with 4 bits and would run from 0/15 to 15/15. So we have 16,000 probabilities tables, each with 64 entries and each entry defined on 4 bits. The memory to hold that would need 22 bits. I understand such computations are somewhat tedious. I think two lessons can be drawn from this: 1/ The computing requirement for uploading quality neurons is well in the range of present day technology. 2/ The serious thinking is no more at the philosophical level or even the biological data collecting, it is at the electronics implementation state of the model. It bite a lot! Yvan Bozzonetti. Content-Type: text/html; charset="US-ASCII" [ AUTOMATICALLY SKIPPING HTML ENCODING! ] Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=26096