Credit: E. MAGUIRE ET AL.

In terms of mental processes, how do you get from A to B? This question of navigation has been tackled by Eleanor A. Maguire and colleagues, who report their latest findings in the 8 May issue of Science (280, 921-924; 1998). Using positron emission tomography they have mapped brain activity as people find their way through a familiar, yet complex, virtual-reality town.

Subjects were allowed to get their bearings in the virtual town (pictured), and they were then asked to head directly towards a goal. Increased blood flow was found in the right hippocampus and inferior parietal cortex of people who successfully completed this task, indicating that these two regions allow navigation to an unseen goal.

Activity was also seen in these areas of the brain when some of the routes to the goal were blocked, forcing the subjects to make a detour. In this case, the left frontal cortex was activated as well, and the authors infer that this region is involved in planning and making decisions. They also studied average speed, measured in virtual metres per second, and found that it correlates with activity in the right caudate nucleus. So this region probably helps people to get where they're going quickly.

What Maguire and colleagues now have is a map of the areas in the brain that support navigation. These findings agree with results from monkeys and rats, and also with studies of London taxi drivers asked to recall complex routes around the city — all of which goes to show that some experiments on rodents really do bear directly on the human rat race.