How does the brain navigate?
Humans have been able to find their way long before the GPS was invented. We have long known that information is sent from all our joints via the cerebellum to the cerebrum and that it helps us know where we are in a room, even with our eyes closed. However, that’s not enough to explain how we find our way to the Louvre the first time we are in Paris or find our way to work every day. There is something else.
Deep inside the temporal lobe, on both sides of the brain, there’s a structure that looks a bit like a seahorse: the hippocampus. The hippocampus has been so well-known for its importance to memory that it was believed taxi drivers in London had a larger than average hippocampus due to the enormous number of street names they have to remember.
But it doesn’t help to memorise street names when you are finding your way. London’s taxi drivers are expected to always know exactly where they are in relation to countless sights and places of interest. When you step into one of the black taxis, you can expect to be driven the shortest distance to anywhere in London. And that’s without any other aid than the driver’s own brain.
Two brain areas help you navigate
In 2014, Norwegian husband-and-wife researchers May-Britt and Edvard Moser were awarded the Nobel Prize in Medicine together with Britain’s John O’Keefe. O’Keefe has identified the hippocampus as not only important for memory. He has shown that we have cells in this seahorse that send out signals when we are in a certain place.
So, when you walk around your bedroom, there are nerve cells in the hippocampus that “yell out” each time you are at the corner of your bed, while there are others that “yell out” when you are over at the window. He labelled them place cells and showed that they make up the brain’s positioning system.
While O’Keefe started an important period of detecting how the brain’s navigation system works, May-Britt and Edvard Moser raised our understanding to a completely new level. They didn’t only research the hippocampus, but also the cerebral cortex located just outside it.
In the cerebral cortex the Mosers found separate nerve cells that send signals to a coordinate system. They found fine-meshed nets in small areas and large loose-meshed nets in larger areas. These nerve cells are called grid cells.
Using the brain to navigate makes it grow
There is reason to believe that these cells are as important to the London taxi drivers as the nerve cells that helps store memory. But are they the same? How often do you remember something without also remembering the place it happened? And did you know that the place cells are activated when you dream? The most commonly used memory technique is about how you connect what you remember to a place.
What makes the brains of the London taxi drivers particularly fascinating is how well the studies demonstrate that the way we use our brains leads to physical change. In the past, one might have thought that those who succeeded in the test known as “The Knowledge” (the legendary London taxi driver exam) had larger than average hippocampi, but no. It actually grows. A group of people who wanted to become taxi drivers had their brains scanned before they started to prepare for the test and were later scanned again after the exam. The scans showed that an area of the hippocampus had grown .
We know that new nerve cell connections are formed when we use our brain, to such an extent that the hippocampus grows when we practise finding our way. It has not been shown that it shrinks when it is not used but, logically, this isn’t likely.
Now how about turning off that GPS on your mobile and using what you have in your brain to keep it in shape?