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Electronic circuit simulates wiring of the human brain (June 21, 2000 1:56 p.m. EDT http://www.nandotimes.com) - Scientists have developed an electronic circuit that mimics the wiring of the human brain in some ways -- an achievement that could improve biological understanding of how nature's most powerful processor works. The circuit, built on a silicon chip the size of a fingernail, is far from the thinking machines of science fiction. For one thing, it cannot learn, the way the brain can. But researchers say it could result in better speech and object recognition by computers. "This is a demonstration of what's possible when circuits compute in biological ways," said Rahul Sarpeshkar, a computer science professor at the Massachusetts Institute of Technology who worked on the project. "We're still far away from building a brain." The findings were published in Thursday's issue of the journal Nature. The project is the culmination of more than two decades of work using transistors and silicon to mimic the natural circuitry in the brain. It is the first time a circuit inspired by the brain's cortex has been created in hardware. Traditional circuits work in one of two ways: They are either digital and specific such as computer processors, or analog and nonspecific like radio amplifiers. Research suggests the brain is able to do digital and analog computing at the same time. Someone watching a highway, for instance, can sort out distinct objects like a police cruiser, and also perceive changes in direction, speed and color. Traditional digital circuits in computers are not nearly as efficient as the brain in perceptual tasks. The latest research, done at Lucent Technologies' Bell Labs in New Jersey, combines both digital and analog processing by using artificial neurons that either excite or inhibit each other based on responses, or feedback, from other neurons. "In one simultaneous circuit, both digital selection and analog amplification can co-exist," Sarpeshkar said. Researchers applied simultaneous electrical currents to two artificial neurons in their circuit. It selected the stronger of the stimuli and suppressed its response to the weaker. That is not unlike, say, a frog choosing which of two flies to eat, the researchers said. And the circuit, like a brain, maintained its selection as the weaker current was increased and the stronger decreased. Another unique aspect of the circuit is that no single element made the decision. "If you take a Pentium chip and cut a single wire, then it would probably stop functioning," said Richard Hahnloser, another MIT researcher. "If you took our circuit, you could cut a wire and it would still work the same." It will be at least 50 years before artificial neural circuitry approaches the abilities of the brain and its 240 billion neurons, Sarpeshkar said. But even simple circuits are useful in demonstrating how biological networks operate, said Dean Buonomano, a neurobiology professor at the University of California at Los Angeles. By MATTHEW FORDAHL, Associated Press Copyright 2000 Nando Media janet paterson 53 now / 41 dx / 37 onset 613 256 8340 / PO Box 171 Almonte Ontario K0A 1A0 Canada visit my website "a new voice" at: "http://www.geocities.com/janet313/"