On Thu, Apr 05, 2007 at 02:03:32PM +0200, Shane Legg wrote: > I didn't mean to imply that all this was for wiring, just that there > is a sizable > about of information used to construct the brain that comes from the > genes.
No disagreement. Apart from sizable. A few gigabases doesn't give you 10^10 bits. And that's about the last time I'm about to mention it. We're totally on the same page, but for some reason you're extremely literally-mindedly focusing on some isolated phrases instead of what I mean. It is rather obvious what I mean, if you don't start looking at isolated phrases and look at word meaning in an absolute way (yes, Blue Brain is about as complicated and large scale as simulations come. No, it is completely trivial on the code size as far as the classic AI school is concerned. The classic AI school doesn't think that cable theory, calcium dynamics or the Nernst-Planck equations are to be considered nontrivial. > If you want to model the brain then this is the kind of information > that you > are going to have to put into your model. Not if you're looking at short-range processes. The genome has zero activity on second scale, and only very little activity on minute scale. Here you can look at the anatomy, and completely ignore how it came into being, and what it does on hour to day scale (which is where the genome comes in). You have to make the model a lot more complex if you just start with a fertilized egg in machina. > Why does the optic tract project to the lateral geniculate nucleus, > the pretectum > and the superior colliculus and not other places in the brain? Why > does the > lateral genicultate body project to striate and not other parts of > cortex? Why does > the magnocellular pathway project to layer 4Calpha, while the > parvocullular > pathway projects to 4A and 4Cbeta? Why does the cerebral cortex > project to > the putamen and caudate nucleus, but not the subthalamic nucleus? I > could > list pages and pages of examples of brain wiring that you were born > with and > that came from your genetics, it's basic neuro science. We're still in vigorous agreement. In fact, in C. elegans each neuron *does* have an address, and the neural network *is* completely deterministic and genetically wired. But that's a 300 cell network in a 1 kCell animal. > I don't clam that all wiring in the brain is genetic, or even a > sizable proportion of it. You sound about as frustrated about this exchange as I am. > What I am claiming is that the brain wiring that is genetic is > non-trivial and cannot > be ignored if somebody wants to build a working brain simulation. On a time scale of seconds to minute you can absolutely ignore the genetic component. You absolutely need the genetic contribution (including full cell dynamics and migration, and molecular target recognition) if you start from nowhere. > You remember the thread: complexity in the code versus complexity > in the > data? The Blue Brain complexity is all in the data. This is very > different > from the classical AI, which tends to obsessionate about lots of > clever > algorithms, but typically does sweep the data (state) under the > carpet. > > Yes, I agree, it's in the "data" rather than the "code". But I don't > accept > that you can say that their model is simple. As neural emulations go, in terms of lines of code, it's probably the largest and most complex there is. In terms of software project complexity, as measured in MLoCs, especially if you exclude the numerics libraries, no. If compared with a classical AI approach to human cognition, it's effectively zero complexity. Yet Blue Brain (with quite a few extensions) is in touching distance of creating the full cognition of an adult, if loaded with the full data set on appropriate hardware. -- Eugen* Leitl <a href="http://leitl.org";>leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE ----- This list is sponsored by AGIRI: http://www.agiri.org/email To unsubscribe or change your options, please go to: http://v2.listbox.com/member/?list_id=303
