It's not so much they've forgotten where they're going. It's just that they can't figure out how to get there.
New research has shown that the brain actually uses two separate parts to navigate from one place to another. The straight-line distance function (where is it from here?) is managed in the entorhinal cortex, but the posterior hippocampus kicks in when you're keeping track of your path and making decisions such as where to turn.
Dr Hugo Spiers and his team at UCL used film footage to recreate the busy streets of Soho in London inside an MRI scanner. Study participants were asked to navigate through the district, famous for its winding roads and complex junctions, while their brain activity was monitored. The researchers analysed brain activity during the different stages of the journey: setting course for the destination, keeping track of the destination while travelling, and decision making at street junctions.
These two regions of the brain are among the first to be impacted at the onset of Alzheimer's disease, which explains why so many Alzheimer's patients lose their way. It is hoped that this reseach will lead to a better understanding and new treatments that will benefit victims of this disease.
The results also reveal what happens in our brain when we use sat nav or GPS to get to a destination. By recording brain activity when participants used sat-nav-like instructions to reach their goal, the researchers found that neither of the brain regions tracked the distance to the destination and in general the brain was much less active.
Does this mean it would be better for our brains if we used our cars' GPS systems less?