Thursday, September 22, 2011

Brain Modeling Computational Trajectory

SGI is a manufacturer of high-performance computers, what might be called small supercomputers. I was listening to their analyst day (I own stock in SGI) this morning and saw an interesting slide, which I reproduce here:
brain modeling projection

With regard to machine understanding, this is the direct assault method. At some point when the human brain is modeled in sufficient detail the construct should display human memory, intelligence, and even consciousness or self-awareness. It is conceivable that a detailed computer model might exhibit artificial intelligence or understanding but leave us still unable to comprehend the essence of what is happening. More likely we will be enlightened and therefore able to construct working machine entities that have true intelligence and understanding, but are not exactly modeled on the human nervous system.

There are different levels for modeling biological systems of neurons and brain matter. We might model on the atomic, molecular, sub-cellular, cellular, or neural-functional level. It is not clear what level of detail is assumed in the SGI projection. Best guess is that is has a model for individual neurons, but the complexity is added by adding additional neurons to the network. That would be the main difference between modeling a "cellular neocortical column," a mesocircuit, a rat brain, and a human brain.

SGI already makes computers for researchers in this field. Of course other vendors' computers can be used. The advantage SGI brings to the table today is the ability to build a large model in computer memory chips (the processors see a big, unified memory), as opposed to hard disks.

I would be very impressed if someone could correctly model a functioning rat brain by 2014. Keep in mind that just because the computer power is available to do it, does not mean that any given team's model is correct. I wonder what proof on concept would consist of? To test such a brain you would need a test environment. That might be a simulation, but it could also be robotic. Keep in mind that much of what a rat brain does relates not to what we think of as awareness of the environment, but to maintaining body functions.

Another issue is the initial state problem. Suppose that you "dissect" a rat so that you know the relative placement of every neuron in its central nervous system. Still, to make your model work, you would need a functional initial state for all the the cells. You need to know how synapses are weighted. Probably someone is working on the boot-up of mammal brains during embryonic development. Even just getting the genetically re-programmed neurotransmitter types for each synapse to each cell seems like a more difficult problem that making a generalized computer model based on a neural map plus a generalized neuron.

Apparently there is plenty of work on this project for everyone.

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