In the UK, volunteers underwent a series of simulated tests while fMRIs captured their brain activity. Participants were shown movies of where they were, given a goal of where to go, and then told to either make a left or a right to reach their end destination.
When the volunteers were navigating on their own - without GPS - researchers noted spikes of activity in the hippocampus, which is involved in memory and spatial navigation; and in the prefrontal cortex, a key area for planning and decision making.
Then, when the participants were using GPS, the hippocampus and prefrontal cortex went completely inactive. This told the researchers that, when GPS does the thinking and planning for you, your brain basically checks out.
Using the hippocampus is super important, because we suspect it stores mental maps, sort of like our brain's very own GPS. It help us remember where we've been and where we're going in 3-dimensional space. The hippocampus helps us picture what's in front of us, and the prefrontal cortex helps us decide which way we should turn.
These findings corroborate another study which found that when we rely on GPS, we stare at our screens way more and disengage from the outside world. Do you remember what it was like to drive before GPS? We had to work hard to pay attention to our surroundings, assemble pictures in our heads, remember landmarks, roads, intersections and we had to improvise quicker routes all on our own. But when we rely on GPS, we're focusing more on the blue lines and dots on a screen than on the journey itself.