Retrospectacle: A Neuroscience Blog

In a recent article on CNN, it was mentioned that while GPS navigation is becoming quite “the” thing to have, London cabbies want none of it. GPS systems were just allowed into cabs earlier this year, but very few drivers have opted for them; they prefer to rely on their own memory rather than any device prone to glitches. There’s a good reason they should do exactly that.

Every one of London’s cabbies has to take the grueling test known as “The Knowledge” in order to get a taxi license. The test consists of learning 320 routes as well as the city’s many confusing streets, shortcuts, and alleys.

The test is so tough — it can take up 34 months of study, albeit part-time, to pass — that academic studies have shown part of the brain of successful applicants actually enlarges.

Scientists found London taxi drivers have a larger hippocampus, the part of the brain associated with navigation, than other people.

This blurb refers to a 2000 Maguire et al. study published in PNAS, entitled “Navigation-related structural change in the hippocampi of taxi drivers.” (More below the fold!)

Essentially, the researchers compared structural MRIs of London cabbies’ brains with the brains of controls. The cabbies (who all passed “The Knowledge” test) were assumed to have “extensive navigational experience” while the controls were not. Their findings indicated that the posterior hippocampi (thats plural for hippocampus!) of the cabbies were significantly larger than controls, while the anterior hippocampi region was larger in controls.

i-8752ef26d93a5b824bec1741d10492f9-cabbie brain.bmp

It is of note that a greater difference was seen in the left hemisphere hippocampus versus the right hemisphere. This can likely be attributed to the fact that only right-handed cabbies were tested, which indicates that their left hemisphere is dominant in handedness and perhaps spatial preference. (The cut-off part on the y-axis says “Hippocampal cross-sectional area”).

In addition, posterior hippocampal size correlated positively with the time spent as a cabbie, and anterior hippocampal size correlated negatively!

i-b4d272afc8b1b57b42bc08748f9744da-cabbie 2.bmp
For better resolution, a popup: View image

These findings make sense when you consider that posterior hippocampus is thought to store information regarding spatial representation of an environment, and has been proven to expand in people who depend on this skill.

In humans, as in other animals, the posterior hippocampus seems to be preferentially involved when previously
learned spatial information is used, whereas the anterior hippocampal region may be more involved (in combination
with the posterior hippocampus) during the encoding of new environmental layouts.

This is a fascinating finding which substantiates a model, as well as illustrates the ability of the adult brain to remain plastic and adapt to complex environments. Hat tip to Darkman.

Comments

  1. #1 JaysonB
    August 15, 2006

    Are you done with being a sick Shelley?

  2. #2 Shelley Batts
    August 15, 2006

    Yes, thank you for asking! No more T-Bell for me for awhile. Just because its “Mexican” doesn’t mean it goes well with Tequila, either. FYI.

  3. #3 JaysonB
    August 15, 2006

    Oh dear shelley, you should know by now…………tequila doesn’t go with anything that doesn’t involve regretting it the morning after.

  4. #4 Shelley Batts
    August 15, 2006

    Yes, a wise (wo)man surely said, “You never buy Tequila, you only rent it.”

  5. #5 The neurophilosopher
    August 16, 2006

    A good university friend of mine did his final year undergrad project, and his PhD, in the lab which carried out these studies. He’s been in the same lab ever since, using fMRI to investigate spatial memory.

    I once volunteered as a subject for his experiments. He was using an altered version of a computer game called Doom to test subjects’ spatial memory.

    I first sat at a computer and navigated through a virtual town, meeting various characters en route, who gave me objects.

    Then I was put in the scanner (which after nearly an hour, began feeling like a coffin!) and shown locations, characters or objects from the computer game. I was required to remember which character I had met at a particular location, or what object I was given by a particular character, or the location in which I was given an object etc., etc.

    The idea was that the performance of controls would be compared with that of people with Alzheimer’s. As I remember, I performed so well that my friend had to change the parameters of the task!

    I also have a friend who drives a black taxi. He spent 4 years memorizing the routes – a PhD in streetology? – and is very proud of his knowledge of London’s streets.

    I sometimes helped him with learning the routes. He’d give me a book of routes, and I’d look at them while he recited one of the routes off the top of his head.

    “Left at such & such street, bear right here, straight forward there…” etc. He memorized all the routes by rote learning (or ‘parrot fashion,’ as it’s sometimes called – appropriate for you, Shelley!).

    People doing the knowlegde not only have to learn those 320 routes, they also have to learn what are called ‘points,’ or landmarks such as tourist attractions and nightclubs.

    I once asked him if he’d like to participate in the research my other friend was carrying out. When he found out that he’d only be paid ?10 an hour, he declined, saying that he could earn much more from an hour’s-worth of fares in his taxi!

  6. #6 film izle
    October 11, 2008

    thanks for you. very..