One of the boldest brain-modelling projects ever attempted is about to get under way in Switzerland. A team of neuroscientists plans to use a supercomputer to create a biologically realistic simulation of the neural circuits responsible for higher mental processes in humans and other mammals. But experts elsewhere are divided about its chances of success.

Most brain models focus either on large- or small-scale features. Some teams have connected huge networks of simple units to recreate brain functions such as vision, for example, whereas others have built detailed computer simulations of individual neurons. Now a team from the Swiss Federal Institute of Technology in Lausanne (EPFL) will use the IBM supercomputer Blue Gene/L in an attempt to combine both approaches.

“This is one of the most ambitious computational-neuroscience projects ever planned,” says Alain Destexhe, a modeller at CNRS, France's main basic-research agency, in Gif-sur-Yvette. “Blue Gene is one of the most powerful computers ever made available to neuroscience.”

The Blue Brain Project will simulate part of the neocortex, the intricately folded region on the outside of mammals' brains. The Swiss team will model a column of cells from the rat neocortex, the animal for which the most detailed data are available. Each column is just 2 millimetres high and half a millimetre in diameter, but contains some 10,000 cells connected by 5 kilometres of fibres. In both humans and rats, these columns form a basic circuitry that is repeated across the cortex and controls everything from vision and movement to planning.

“It's as if in evolution this system was cloned and duplicated in mammals — it makes up 80% of the human brain,” says Henry Markram, who leads the project at the EPFL. “The more we look at the neocortex, the more we are in awe of it.”

IBM has built several Blue Gene computers for use in research (see ‘Virtual Big Bangs and digital mushroom clouds’). The EPFL's version, which is worth US$10 million and should be switched on next month, is a rack of four refrigerator-sized units, each containing more than 1,000 processors. It can process over 22 trillion operations per second. If running today, it would probably be the fourth most powerful machine in the world.