Key changes in the brain enable taxi drivers to remember the best routes, a study suggests.
Drivers of London's black cabs have a famed knowledge of the city
Researchers in the United States have found that driving can trigger certain cells into action.
These cells or neurons are activated in areas of the brain associated with learning and memory.
Writing in the journal Nature, the researchers said this may explain why taxi drivers can remember even the most obscure routes.
Dr Michael Kahana of Brandeis University and colleagues studied seven people while they played a taxi-based computer game.
As part of the game, the players had to drive around a virtual town, search for passengers and deliver them to various shops.
As they did so, the researchers measured the activity of key neurons in their brains.
They found that neurons in the hippocampus responded to particular locations.
The hippocampus is associated with learning and memory.
They found that neurons in the parahippocampal cortex responded more to landmarks.
Tests on rats have shown similar results.
"Cells throughout the frontal and temporal lobes responded to the subjects' navigational goals and to conjunctions of place, goal and view," they said.
Other studies have also shown that regular driving can affect the brain.
Three years ago, researchers at the Institute of Neurology in London showed that cab drivers' grey matter enlarges and adapts to help them store a detailed mental map of the city.
Taxi drivers given brain scans by scientists had a larger hippocampus compared with other people.
The scientists also found part of the hippocampus grew larger as the taxi drivers spent more time in the job.
Dr Eleanor Maguire, who led that study, described these latest findings as interesting.
"It is a very interesting paper whose findings seem to be
entirely in line with what we have shown with our previous work, namely that the hippocampus is crucial for navigation, from rats to humans," she told BBC News Online.
"As far as I know, this is the
first study in humans to look at the response of individual neurons in the hippocampus and other areas during interactive navigation."
She added: "It is very encouraging that the data sit so well with ours."
In London, black-cab drivers can spend years training before they are allowed to get behind the wheel of a taxi.
In order to drive a traditional black cab in London drivers have to gain "the knowledge" - an intimate acquaintance with the myriad of streets in a six-mile radius of Charing Cross.
It can take around three years of hard training, and three-quarters of those who embark on the course drop out.