My Aunt Peggy recently shared this interesting story with me about researchers studying London cab drivers to learn about how their brain's work. They're looking for clues about how Alzheimer's disease starts and unfolds. You'd think at this point we'd already understand the disease well enough to not need seemingly esoteric studies, but we don't. Alzheimer's is an incredibly complex disease. It seems that whenever we think we have something figured out, we're soon back at the drawing board. So novel ways of investigating the disease are still welcome.
It's a lot harder to get a permit to work as a cabbie in London than it is here in our town. It's been that way for a long time, since 1865. (Maybe it was easier back then when cabbies drove horse and buggy?) License applicants must demonstrate a knowledge of 400 possible routes within six miles of Charing Cross -- the center of London.
If you read Beating the Dementia Monster, you know that the hippocampus is the structure in the brain that keeps track of where you are in time and space. It encodes a map of the floor plan of a new hotel where you're staying or the streets of your town. (It's also important to memory.) So, to pass their license exam, London cabbies must memorize the layout of the city streets and be able to mentally construct routes between any given points. Without a GPS. And there are somehow 26,000 streets to consider. A London cabbie's hippocampus is a pretty busy place.
If you've followed my experience, you know that the hippocampus shrivels up in people with Alzheimer's disease. (Unless you apply the tools of the Dementia Toolkit in Beating the Dementia Monster.) But it's also known that the hippocampi of London cab drivers actually grow. Apparently, the more the hippocampus is used the more new neurons will blossom from stem cells located there.
Is that true? And if so, does a growing hippocampus correspond to better memory and cognition? This makes sense, but it turns out that the relationship is not at all clear in research. So can we learn more from the cabbies?
In a project from University College London called "Taxi Brains," they're putting about 30 taxi drivers in MRI machines and then having them construct taxi routes throughout London. I'm guessing these are "functional MRIs" that show levels of activity in different parts of the brain as the subject solves mental problems.
So what do they hope to accomplish with this investigation? According to the article, they're looking for new ways to detect the onset of Alzheimer's disease. This makes sense, since, more often than not, the first symptoms of disease are in those cerebral functions driven by the hippocampus. Most notable is memory, since it's the hippocampus that translates short term memories into long term memories.
Are we seeing any interesting results yet? According to this story from the BBC, the rear quadrants of both the left and right hippocampi of London cabbies was larger than those of control subjects, but the frontal quadrants were actually smaller.
This research has gotten some recent attention, but the researchers have been at it for a while. According to this Scientific American article from 2011, how the cabbies' hippocampus changes has been known for a while. What has also been known is that, as the cabbies increase their spatial memory, they do less well on a memory test called the Rey-Osterrieth Complex Figure Test. (I've been given this test annually since 2015.) A thought is that as one part of the hippocampus grows another part atrophies -- taking with it some cognitive ability.
I couldn't find any information on whey they'll publish the results of the latest tests. I'll be on the lookout for some news.
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