Since the late 1800s, if someone wants to be a taxi driver in London they have to pass ‘The Knowledge’ and usually this means riding around London on a scooter for a couple of years or more, learning the city. During this time they learn 25,000 streets and all the landmarks, junctions etc. along them. They must know the best way to get from any A to any B within a 6 mile radius of Charing Cross. The qualification includes a written test and 12 or so oral tests. Then, after a few other checks, they can start to drive a London taxi. The question is – what does this do to someone’s head?

One result is a very large hippocampus. A ScienceDaily item summarizes some research on experienced London cabbies.

“The study showed that a region of the hippocampus was enlarged in London taxi drivers compared to the general population… the difference is linked to ‘The Knowledge’ of the city’s 25,000 streets built up by taxi drivers over many years…

Taxi drivers used the virtual reality simulation to navigate the streets of London whilst lying in an fMRI brain scanner. The researchers found that the hippocampus is most active when the drivers first think about their route and plan ahead. By contrast, activity in a diverse network of other brain areas increases as they encounter road blocks, spot expected landmarks, look at the view and worry about the thoughts of their customers and other drivers.

“The hippocampus is crucial for navigation and we use it like a ‘sat nav’,” says Dr Spiers from the Institute of Behavioural Neuroscience at UCL. “London taxi drivers, who have to know their way around hundreds of thousands of winding streets, have the most refined and powerful innate sat navs, strengthened over years of experience.”

In their study, Dr Spiers and Professor Maguire found that a part of the brain called the medial prefrontal cortex increased its activity the closer the taxi drivers came to their destination…Inside the hippocampus and neighbouring brain areas scientists have identified three types of cells which, says Dr Spiers, make up the sat nav. These are called place cells, head direction cells and grid cells.

Place cells map out our location, lighting up to say ‘you are here’ when we pass a specific place. There are thought to be hundreds of thousands of place cells in the brain, each preferring a slightly different geographical place. Head direction cells act like a compass, telling us which way we are facing. Grid cells … tell us how far we have traveled using a grid-like pattern akin to how we use latitude and longitude for navigation.”

Our whereabouts is something we are often very conscious of. Our consciousness also seems to never loss its spatial quality. Everything we are conscious of seems to have a location in our visual space or some other space.