IT'S certainly different, some might even say distasteful, but there's no doubt that Steve Potter has the strangest lab rat around. Its body is a virtual one, running around inside a computer generated world. And its brain is like nothing you've ever seen—an amorphous mass of brain cells from a real rat, living in a shallow glass dish and wired up to the computer. Potter wants to see if the "rat" can learn its way around, which means the neurons must sense and remember the rat's virtual world and control its movements, just as a real brain would.

For decades, neuroscientists have struggled to understand just how tangles of neurons let us carry out everyday wonders such as learning and moving. They've studied the behaviour of single neurons, eavesdropped on the electrical signals from various areas of the brain and even scanned the brains of people carrying out complex tasks. ...