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Monday, February 12, 2007 Building the Cortex in SiliconModels of the brain built from specially designed computer chips could reveal the secrets of our cerebrum. By Emily Singer
An ambitious project to model the cerebral cortex in silicon is under way at Stanford. The man-made brain could help scientists understand how the most recently evolved part of our brain performs its complex computational feats, allowing us to understand language, recognize faces, and schedule the day. It could also lead to new neural prosthetics. "Brains do things in technically and conceptually novel ways--they can solve rather effortlessly issues which we cannot yet resolve with the largest and most modern digital machines," says Rodney Douglas, a professor at the Institute of Neuroinformatics, in Zurich. "One of the ways to explore this is to develop hardware that goes in the same direction." Neurons communicate with a series of electrical pulses; chemical signals transiently change the electrical properties of individual cells, which in turn trigger an electrical change in the next neuron in the circuit. In the 1980s, Carver Mead, a pioneer in microelectronics at the California Institute of Technology, realized that the same transistors used to build computer chips could be used to build circuits that mimicked the electrical properties of neurons. Since then, scientists and engineers have been using these transistor-based neurons to build more-complicated neural circuits, modeling the retina, the cochlea (the part of the inner ear that translates sound waves into neural signals), and the hippocampus (a part of the brain crucial for memory). They call the process neuromorphing. Now Kwabena Boahen, a neuroengineer at Stanford University, is planning the most ambitious neuromorphic project to date: creating a silicon model of the cortex. The first-generation design will be composed of a circuit board with 16 chips, each containing a 256-by-256 array of silicon neurons. Groups of neurons can be set to have different electrical properties, mimicking different types of cells in the cortex. Engineers can also program specific connections between the cells to model the architecture in different parts of the cortex. "We want to be able to explore different ideas, different connectivity patterns, different operations in these areas," says Boahen. "It's not really possible to explore that right now." Boahen ultimately plans to build chips that other scientists can buy and use to test their own theories of how the cortex operates. That new knowledge can then be built into the next generation of chips.
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Comments
spicker on 02/12/2007 at 4:57 AM
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TRAyres on 02/13/2007 at 4:59 AM
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What, its not good enough for you to only have modelled two parts of the brain, they have to get the whole thing done before you take notice? Let me guess: You aren't very good at investing. Just a thought.
Honestly, saying this kind of research is hot air is like saying these 'darn computers' are just passing fads.
spicker on 02/13/2007 at 5:30 AM
4
Do not mistake, I think it is great that people model the various parts of the brain. However, one needs to carefully look at the assumptions and conditions set up for the model.
When Kwabena Boahen is planning to create 'a silicon model of the cortex' I think it is a bold statement to claim that he replicated it. No doubt he will find interesting answers and I am eager to see the results but also hesitant to expect the final solution.
When a transistor models a neuron, it models parts of its electrical properties and perhaps also wiring pattern. But seldomly, it takes into account all of its intricate chemical and physical functionality. The temporal aspects stemming from deprivation of neurotransmitter, enhancement of synapses, gene expression leading to additional receptors and the like, are most often not inherent in the silicon models presently suggested and I would question whether they are part of Boahen's but will appreciate it if it is the case.
No doubt Boahen's model will bring further understanding but I miss to see why this attempt is more special than the silicon attempts made previously.
NNemec on 02/13/2007 at 7:37 AM
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Of course, one can try to model at various levels of refinement, but still everything that you put into the computer and call it "neuron" will be a model, unless it is a atom-by-atom simulation.
Obviously, such a complete simulation is impossible with todays and probably also next week's technology. But even more: it would not help us a bit in understanding. A replica is - by definition - exactly as complex as the original, so it is exactly as complicated to understand.
Only a reasonable model helps understanding. Scientists have to try different models to find out which aspects are important to capture the working of the original.
bshi on 02/13/2007 at 11:00 AM
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> of refinement, but still everything that you put
> into the computer and call it "neuron" will be a
> model, unless it is a atom-by-atom simulation.
Nope; the atom is still a physical model.
spicker on 02/13/2007 at 3:31 PM
4
Sorry for the confusion.
I was triggered by the title 'Building the cortex in silicon' and failed to be as brief as the reply from stevenzenith.
ms on 02/12/2007 at 7:22 PM
54
reluctantelitist on 02/20/2007 at 7:44 AM
1
rajamouli2000 on 02/13/2007 at 2:58 AM
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randcraw on 02/13/2007 at 11:19 AM
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Also, large numbers of CPU ops/second are an easy claim when you ignore RAM bandwidth. To wit: a CPU with 64 bit registers + 3 GHz clock = 192 GigaOps. Multiply that by 3-4 functional units per CPU, and your laptop approaches a TeraOp.
So is every three year old PC a supercomputer?
Todd on 02/13/2007 at 12:37 PM
5
According to Ray Kurzweil, a desktop around the year 2020 should have the computing capacity to function at the speed of the human brain (2*10^16 cps).
There also have been models of the cerebellum, not just the inner ear.
spicker on 02/14/2007 at 3:50 AM
4
... or when feeling discomforted about having been too sarcastic in a comment to an article in a magazine.
stevenzenith on 02/13/2007 at 12:15 PM
2
WickedWitch on 02/13/2007 at 5:46 PM
1
vznuri on 02/14/2007 at 7:39 PM
1
computing? maybe something hebbian, or
similar to the SVD, singular value decomposition.
check for & discuss related cutting edge developments in algorithmics & mathematics at
the theory-edge mailing list,
http://groups.yahoo.com/group/theory-edge/
dallassmeltser on 03/15/2008 at 5:35 PM
1
Make a real brain like the rat heart.Then the testing could be better and easier..