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Brains change structure with use -

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Brains change structure with use

Parts of London taxi drivers' brains have been shown to get larger as the drivers learn and absorb
all the information required to be efficient taxi drivers. The brains' structure changes.


Robyn Williams: Let me just reflect on something that Susan Greenfield often says about the ways in
which taxi drivers seem to have a larger hippocampus because they've got such knowledge of usually
London, an incredible knowledge, and in fact before they become taxi drivers the idea is that the
hippocampus is smaller, and as they learn the information it gets bigger. Is that story more or
less accepted these days?

Hugo Spiers: That's what the research is showing. So Eleanor Maguire and her colleagues in the year
2000 discovered that when she compared the structure of taxi drivers' brains to match control
subjects, that within their brains only the hippocampus was different. And the posterior end of it
seemed to be bigger and the anterior end of it seemed to be smaller. So it wasn't just that it got
bigger, it was actually the structure changed, and intriguingly the right posterior hippocampus got
bigger the longer they had spent being taxi drivers. So it seemed to be linked to their experience
in the job.

Following up on that study, Eleanor has carried on doing a number of studies, one I was lucky to be
involved in with Katya Willett comparing these taxi drivers' brains to London bus drivers. London
bus drivers are a wonderful group to compare taxi drivers to in that they also have to drive and
navigate through London streets but they don't really have to think about the multitude of possible
routes, they have to follow a set route. But they also have to deal with enraged customers, the
roar of the traffic and the pollution of London streets.

So compared to these bus drivers, the group found the same effect that the taxi drivers'
brains...the posterior hippocampus was again bigger in this other new sample of the taxi drivers.
So it appears to be a robust finding that there is some sort of structural change in taxi drivers'
brains, and following up on it is an intriguing question. My own research has been looking at how
they use the hippocampus, what happens to the activity within that region and other regions around
it as the taxi drivers navigate.

Robyn Williams: Of course as the taxi drivers navigate it would be a pretty hazardous thing to have
it while they're driving through London. So how did you solve that problem?

Hugo Spiers: That was a huge challenge. So to get brain activity you have to use magnetic resonance
imaging, M.R.I. scanners, and those are huge big devices that you can't take any metal into, so you
certainly can't put one of those in the back of a London cab. So you have to take the world of the
London cab and the streets of London inside the brain scanner. We used a commercial videogame The
Getaway that had been developed by Sony in 2002 where they'd simulated in a high degree of accuracy
London's vast number of streets using ordinance survey maps and all sorts of digital capture
software and so on. But we were able to then, using this video game, have subjects, our taxi
drivers, drive through this virtual simulation of London and capture in our scanner their fleeting
brain activity as they drove through the city.

Robyn Williams: So what were you trying to find out exactly? You already established that the
hippocampus is bigger, what else did you try to establish?

Hugo Spiers: With these subjects, because they're experts we were able to verify they would
navigate well through these streets with a high degree of accuracy, so we were able to for the
first time then really look at what happens as individuals navigate in a familiar setting. And what
happens from moment to moment...prior to the study we really didn't know anything about what
happens as you navigate from second to second. So I was able to pull apart the brain activity, what
was happening in taxi drivers' brains, from second to second, and to do that was another technical
challenge because how do we know what's going on, what's happening to them? And the trick we came
up with was after the taxi drivers had navigated through the virtual simulation, take them out and
supply them with lots of tea and coffee and interview them with a video replay of exactly what they
had been doing inside the scanner.

In this video replay I asked them to describe what they remember thinking during the original
navigation episode, and from these descriptions of their thoughts, across a set of 20 taxi drivers
we could see consistent recurring types of thoughts. And then once we'd identified these we could
look back and find what was the pattern of brain activity that accompanied those thoughts. So, for
example, thinking about your destination, how you are going to get there, we saw just in those
moments increased activity in the hippocampus but at no other time in navigation. So this bit of
the brain that that changes in these taxi drivers is very active for a very brief moment of
navigation in the city but otherwise silent.

Robyn Williams: So they set that in the beginning and they've got that navigation set and that's
done, and the rest is sort of automatic and they think about beer and sex and whatever else

Hugo Spiers: Yes, we didn't capture a lot of thoughts about beer and sex unfortunately in our
scanner, I think they were so focused on getting to the destination. We did capture all sorts of
thoughts. So, for example, when they spot something they didn't expect to see we see activity in
the right prefrontal cortex, another part of the brain very active during these moments. But
conversely when they saw what they were expecting to see, the landmark that was going to lead them
there, we saw another bit of the brain, the retrosplenial cortex and other regions active. So those
are just some of the examples.

But there's a whole range of different thoughts and brain activity patterns being covered,
including when they, for example, thought about their customers' thoughts. They're not just
navigating looking at the streets, they're sometimes thinking about other things, and activity
during these periods was associated with an area called the posterior superior temporal sulcus, a
bit of a mouthful, but it's a part of the brain known to be part of a region of networks involved
in social cognition, which neuroscientists are currently obsessively trying to understand, social
cognition, and we could see it active in these fleeting moments in our taxi drivers' journeys, they thought about customers' thoughts, this superior temporal sulcus was very

Robyn Williams: What about the difference between taxi drivers and the rest of us in terms of
navigation? Is there anything you can tell us about how effectively to use our brains navigating so
that we don't get lost and get mucked up?

Hugo Spiers: Surprisingly there's not a lot...we didn't really compare in this study the taxi
drivers directly to non taxi drivers. I checked that the approach I'd taken worked and we got the
same sort of thoughts with non taxi drivers. To all intents and purposes it seems that you get the
same sorts of thoughts in people who aren't taxi drivers, it's just that with taxi drivers; boy,
can they bring a lot of information to hand when they need to navigate!

They spend two to four years training to pass an exam in London called The Knowledge, and they
drive around on little mopeds trying to learn it. They have all sorts of little techniques for
imagining moving in their mind's eye through all the streets, picture all the places along the
routes, that helps them learn. So there are established ways taxi drivers have developed to try and
help them learn, but there is nothing like hard graft, getting out there and doing it day after day
after day, driving through those streets and picking it up.

One thing our research did show that intrigued me about the taxi drivers is the minimisation of
effort. Really a lot of them don't want to waste too much of their time thinking and obsessing
about their routes. They become very efficient at optimising, just making sure that they think
first about which direction they need to go in getting the car in the right direction, then
worrying about which major points they need to go through. It's something that I'll have to look
into in more detail later.

Robyn Williams: Final question, a question of animals, I'm thinking of the godwit that flies from
New Zealand 12,000km though the most amazing distances, obviously, and also knows when to turn left
in the North Pacific, and then flies all the way back again and manages to land within just a few
kilometres of where it's supposed to be, doing some weather predictions at the same time and
surfing on the lows. That's an incredible feat.

Hugo Spiers: There are some incredible and remarkable navigational feats that animals can do around
the world. Yes, some of them use the magnetic fields of the Earth to help navigate, others can
sense the current waves under the sea. Sea turtles use the currents in the sea to help them
navigate vast distances in straight lines. So above the skies, on the Earth and beneath the oceans,
animals are all making their way vast distances doing remarkable things. We use our eyes and our
ears predominantly to help us navigate around, I guess.

Part of the lecture I'm going to give today at the British Association Science Festival
lecture...I'm going to talk a little bit about how desert ants navigate because they are absolutely
fantastic. These little ants, Cataglyphis, can travel half a kilometre over a featureless desert,
scurrying all around in different directions, but then once they find their food they can return in
a nearly dead straight line back to their nest. It's the kind of thing that scientists marvel at
and spend their painstaking time trying to capture little ants and chase them. Well, I've spent my
time chasing taxi drivers who are also quite hard to get to convince to come inside a brain
scanner. So yes, there's a certain parallel there, I think, between trying to capture ants and
trying to capture taxi drivers.

Robyn Williams: Huge Spiers is a research fellow at the University College London, and a you heard
he gave a lecture on navigation at the British Association Festival of Science in Liverpool.