LONDON taxi drivers are helping neuroscientists understand how people create
a 鈥渃ognitive map鈥� that allows them to navigate. The brain鈥檚 cartographer appears
to be the hippocampus, a sea-horse-shaped structure thought to play a vital role
in storing and retrieving memories.
Eleanor Maguire of University College London wanted to find out which parts
of the brain are active when people plan a route. She worked with London taxi
drivers because they probably memorise similar mental maps during their years of
training.
Maguire and her colleagues asked 11 blindfolded taxi drivers to describe the
different routes they would take, for example, from Grosvenor Square to Bank
underground station. As the drivers spoke, the scientists ran scans measuring
brain activity and blood flow. They found that the right hippocampus, along with
several other brain regions, lit up when the cab drivers talked their way
through the best route to take.
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To confirm that the right hippocampus plays a special role in navigation, and
not simply in recalling a sequence of events, the team asked the drivers to
relate the plots of familiar movies such as Top Gun. They also asked
the drivers to describe famous landmarks that they had never visited, such as
the Statue of Liberty, as well as still movie scenes, since the brain doesn鈥檛
have to put these isolated images into a spatial context in order to recall
them.
The drivers鈥� descriptions of films and famous landmarks triggered some of the
same brain regions as the navigational task, but not the hippocampus. 鈥淭hese
regions may be primed to respond to any topographical stimuli,鈥� says Maguire,
鈥渂ut only the hippocampus puts the landmarks in context.鈥� Her findings will
appear in the 15 September issue of The Journal of Neuroscience (vol
17, p 7103).
Previous research on cognitive mapping has included monitoring the brain
activity of rats as they run through mazes, and looking at the abilities of
people with hippocampal damage. Both types of study have suggested that the
hippocampus is the mental map maker, but researchers who monitored the brain
scans of people navigating in environments set up for research have found
inconsistent results.
John O鈥橩eefe, also of University College London, who did many of the early
studies on rats, says Maguire 鈥渄eserves enormous credit鈥� for opening up the
study of how humans navigate through real-world environments. 鈥淟ondon taxi
drivers are fabled to know where everything is,鈥� he says. 鈥淚t鈥檚 an extremely
clever thing that she鈥檚 done.鈥�
O鈥橩eefe notes that there is growing evidence that the hippocampus is
responsible for processing memories specific to a particular time and place. A
report that appeared in Science (vol 277, p 376) in July described
children with early hippocampal damage who could remember general information
about the world, such as arithmetic and history, but not what they had done
earlier in the day.