X-Message-Number: 26012 From: Date: Thu, 14 Apr 2005 02:02:43 EDT Subject: Re: CryoNet #26005 To T Donaldson T. Donaldson: > I honestly don't know just what books > would be best for you toread if you want to learn what we know now about how > brainswork. I would suggest THE NEURON, by IB Levitan and LK Kaczmarek;the > most recent edition of Shephard, NEUROBIOLOGY; and FROMMOLECULES TO NETWORKS > edited by JH Byrne and JL Roberts. Youmay also want to consult a book on > biochemistry I have read Biochemistry from L. Stryer (W.H. Freeman ed.) nearly 950 p. Molecular Biology of the CELL from Albert et al. 1146 p. From Molecule to Networks is half that. >Your TRACs may be able to change 8connections (is that the small number they >have?) but lots of neuronsconnect to many more than 8 others. To be fair, >that's not true for ALLneurons, so the TRACs might sometimes fit. I have not described the TRAC concept yet. There is a preview: A TRAC contains a number of logical cells, each cell has one operational amplifier, this one can be configured along 8 different ways, this is sufficient to implement all basic mathematical fuctions: identity, inversion, adding, multiply, derivate, integrate and so on. Assume we want to simulate two linked dendrite section to form an "Y", using the cable equation. This equation is a sum with 3 terms: two are partial second order derivatives and the last is a simple potential. There would be 2 cells configured as derivative function for the first and second terms. One cell would add them and a last one would add the potential. The total is 6 cells for one cylindrical element. Because the "Y" has 3 sections, there will be 6 x 3 = 18 cells used here. The junction performs an integration, it is done by one more cell. This simple configuration use so 19 TRAC logical cells. What is interesting holds in that: You type the equation in a software window and the computer defines how much cells must be used, how to connect them and what functions they must perform. The basic TRAC has 20 cells, a test board has four TRACs or 80 cells. A real neuron may have 4000 dendrite "Y"s. but they display all the same configuration, so this structure is simple to enter in the computer and a big TRAC may accept it. The trick is that the repetitive structure of TRAC simplifies the mask making of the circuit and one generic component fits all the needs. It is possible to build TRACs in the million of cells range. In the example above one neuron would be simulated with 80,000 TRAC cells. 12 neurons would fit at the same time on a single IC used .1% of the time. In time sharing mode, the integrated circuit would support 12,000 neurons. Current TRAC speed is very low, in the MHz range, it could be multiplied by 100 or more with current technology. There would be then more than one million neurons on a single chip. Multiply that by 10 with comming HEMT transistor technology on IC. And that is not the best use for TRACs, I'll come back on the subject later. 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=26012