The 'sat nav' in our brains
12 September 2008
The brain's navigation mechanism resides in an area know as the hippocampus, which is responsible for learning and memory and famously shown to be different in London taxi drivers in a Wellcome Trust-funded study carried out by Professor Eleanor Maguire at UCL (University College London).
The study showed that a region of the hippocampus was enlarged in London taxi drivers compared to the general population. Even bus drivers do not have the same enlarged area, and general skill at navigating is not related to hippocampus size, suggesting that the difference is linked to 'The Knowledge' of the city's 250 000 streets built up by taxi drivers over many years.
In a follow-up study, Dr Spiers and Professor Maguire used the Playstation 2 video game ‘The Getaway’ to examine how taxi drivers use their hippocampus and other brain areas when they navigate. Taxi drivers used the virtual reality simulation to navigate the streets of London while 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. However, it is still unclear how the brain knows which way we need to go to reach our destination, and it is this question that is the subject of Dr Spiers's ongoing research, also funded by the Wellcome Trust.
Inside the hippocampus and neighbouring brain areas scientists have identified three types of cells that, 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, discovered in 2005 by Professor Edvard Moser’s group at the Norwegian University of Science and Technology, tell us how far we have travelled, using a grid-like pattern akin to how we use latitude and longitude for navigation.
"Over the millennia, humans have invented and utilised many different navigation tools such as maps, compasses and latitude and longitude," says Dr Spiers. "Nature is far ahead of us and seems to have developed these tools inside our heads for our survival."
In a further twist on the research, Professor Maguire and Dr Spiers studied a taxi driver whose hippocampus had been damaged by a viral infection, leading to amnesia. While he was able to navigate using major or 'A' roads, he was no longer able to navigate through the winding, minor streets of the capital.
Dr Spiers gave the Charles Darwin Award Lecture at the BA Festival of Science 2008, University of Liverpool.
Image: Dr Eleanor Maguire and Dr Hugo Spiers with the videogame they used in their research; Wellcome Images
Contact
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Media Officer
Wellcome Trust
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c.brierley@wellcome.ac.uk
Notes for editors
About the BA Festival of Science
The
BA Festival of Science will take place in Liverpool from 6-11 September bringing over 350 of the UK’s top scientists and engineers to discuss the latest developments in science with the public. In addition to talks and debates at the University of Liverpool, there will be a host of events happening throughout the city as part of the European Capital of Culture celebrations.
About the Wellcome Trust
The
Wellcome Trust is the largest charity in the UK. It funds innovative biomedical research, in the UK and internationally, spending over £600 million each year to support the brightest scientists with the best ideas. The Wellcome Trust supports public debate about biomedical research and its impact on health and wellbeing.
About UCL
Founded in 1826,
UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender, and the first to provide systematic teaching of law, architecture and medicine. In the Government's most recent research assessment exercise, 59 UCL departments achieved top ratings of 5* and 5, indicating research quality of international excellence.
UCL is in the top ten world universities in the 2007 THES-QS World University Rankings, and is the third-ranked UK university in the 2007 league table of the top 500 world universities produced by the Shanghai Jiao Tong University. UCL alumni include Marie Stopes, Jonathan Dimbleby, Lord Woolf, Alexander Graham Bell and members of the band Coldplay.