Simulated brain mimics human quirks

A new computer simulation of the brain can count, remember and gamble. And the system, called Spaun, performs these tasks in a way that’s eerily similar to how people do.

Short for Semantic Pointer Architecture Unified Network, Spaun is a crude approximation of the human brain. But scientists hope that the program and efforts like it could be a proving ground to test ideas about the brain.  

Several groups of scientists have been racing to construct a realistic model of the human brain, or at least parts of it. What distinguishes Spaun from other attempts is that the model actually does something, says computational neuroscientist Christian Machens of the Champalimaud Centre for the Unknown in Lisbon, Portugal. At the end of an intense computational session, Spaun spits out instructions for a behavior, such as how to reproduce a number it’s been shown. “And of course, that’s why the brain is interesting,” Machens says. “That’s what makes it different from a plant.”

Like a digital Frankenstein’s monster, Spaun was cobbled together from bits and pieces of knowledge gleaned from years of basic brain research. The behavior of 2.5 million nerve cells in parts of the brain important for vision, memory, reasoning and other tasks forms the basis of the new system, says Chris Eliasmith of the University of Waterloo in Canada, coauthor of the study, which appears in the Nov. 30 Science.

Input takes the form of written or typed characters, which Spaun “sees” with its vision system. The incoming information flows through the system, bouncing to and from various brain areas as it gets compressed into clear directions. Then, Spaun makes a decision about what to do. Finally, the decision gets expanded into action — it generates precise instructions on how to write out an answer. Because of the size and complexity of the system, the process is slow — in Spaun’s world, one second of work takes two real hours of computations.