When was the last time you navigated somewhere using a paper map? Or parked at a stop sign in a strange neighborhood, looking vaguely at the sky, trying to retrace how you got yourself into this godforsaken rabbit warren of one-way streets in the first place?
Thanks to the app on that fancy little pocket computer you carry around but call a phone, you no longer have to exercise the part of your brain to use spatial reasoning to work your way out places you're not very familiar with. In fact, a new study published in the journal Nature Communications suggests that satellite navigation, or satnav, effectively "switches off" our hippocampus and prefrontal cortex — the parts of the brain responsible for simulating routes based on prior knowledge, and planning and decision-making, respectively.
The research team from University College London (UCL) stuck 24 participants in fMRI machines and had them navigate through a computer simulation of streets in the city of London. The scientists monitored the subjects' brain activity while navigating from memory versus when they simply followed the directions given to them by a satnav device. It turned out that there were major spikes in the activity of both the hippocampus and the prefrontal cortex when the participants encountered giant roundabouts similar to London's Seven Dials or the Magic Roundabout of Swindon, but those parts of the brain didn't fire up when the satnav fed them instructions.
"If you are having a hard time navigating the mass of streets in a city, you are likely putting high demands on your hippocampus and prefrontal cortex," said lead author Dr. Hugo Spiers of UCL Experimental Psychology, in a press release. "Our results fit with models in which the hippocampus simulates journeys on future possible paths while the prefrontal cortex helps us to plan which ones will get us to our destination. When we have technology telling us which way to go, however, these parts of the brain simply don't respond to the street network. In that sense our brain has switched off its interest in the streets around us."
Previous research has shown that the gray matter in the memory centers of London cab drivers increases during the 3-to-4-year period of training in which they learn all London's 25,000 streets and countless landmarks, resulting in the hippocampus of these drivers being larger than normal.
So, what's going to happen to our hippocampi and prefrontal cortices now that we don't rely on them to help us get around anymore? Will those part of our brain atrophy, shriveling to useless raisins and unable to do the work related to memory capabilities we take for granted? The answer is: We don't know yet.
"Understanding how the environment affects our brain is important," says co-author Dr. Amir-Homayoun Javadi, who ran the brain imaging analysis at UCL, and is now at the University of Kent. "My research group is now exploring how physical and cognitive activity affect brain activity in a positive way. Satnavs clearly have their uses and their limitations."