WASHINGTON, D.C. September 16 -- Immediate left on Puddledock, right on Queen Victoria Street, left on Friday Street. New research for the first time shows through systematic brain imaging tests on London taxi drivers that a human's ability to remember the route to a destination requires the right hippocampus of the brain.
"This research shows that the hippocampus in humans houses the mental maps that we use to find our way around," says the study's lead author, Eleanor Maguire, of London's Institute of Neurology. "The discovery helps to open up the study of human navigation and suggests that different brain networks support different types of memory."
Maguire's study, funded by the Wellcome Trust, is published in the September 15th issue of The Journal of Neuroscience.
"While it has been known for some time that the hippocampus is involved in spatial cognition in animals, Maguire's work is very important because it suggests this also may be true for humans," says Patricia Sharp, a learning and memory expert at Yale University.
In the study, the researchers analyzed spatial navigation by imaging the brains of 11 taxi drivers with positron emission tomography (PET). London taxi drivers have to train for several years and undergo strict testing before they can gain a license to work. "Therefore, they were the ideal people to study in order to ascertain the brain regions that are involved in the use of a well-developed mental map of a large city," says Maguire.
The PET images, which highlight neural activity by measuring changes in brain blood flow, indicated that the right hippocampus was activated significantly when the taxi drivers recalled complex routes, but not during other types of complex memory recall. For example, it was not activated when the drivers were asked to recall the plots of familiar, famous films -- a test that also requires the recall of information involving a sequence of events. The brain areas activated during the film recall test were located in the left frontal lobe. "The results show that the right hippocampus is not merely activated in all types of complex memory recall, but is specially recruited for route recall," says Maguire.
The research also investigates the role of the right hippocampus in navigation. "A network of brain regions may support the construction of a mental map of space, but only the right hippocampus is specifically involved in relating the elements of a route together in an overall framework for navigation," says Maguire. For example, the scientists found that when taxi drivers remembered information about individual world-famous landmarks such as New York's Statue of Liberty, the activated brain regions included the occipitotemporal regions, posterior cingulate gyrus, medial parietal area and parahippocampal gyrus. The route memory test also triggered activation in these brain areas. The right hippocampus, however, was activated only during the route memory test.
In future studies, the researchers plan to investigate further the specific operations that the right hippocampus performs during navigation.
Maguire's co-authors, Richard Frackowiak and Christopher Frith are also from the Institute of Neurology. Maguire and Frackowiak are members of the Society for Neuroscience, an organization of more than 27,000 basic scientists and clinicians who study the brain and nervous system.