A new study reveals that our brains have a "homing signal" mechanism that continually updates itself as we move through our environment. Thus, not only can it tell which way we are facing - like a compass - but it can also tell which way we should face in order to reach our goal.
The study explains why some people are better navigators than others - they have stronger homing signals. This is according to researchers from University College London (UCL) in the UK.
The team reports their findings in the journal Current Biology.
The ability to find our way home or to the nest is a fundamental behavior for humans and other complex animals. And a crucial first step in navigating the journey is knowing the right direction to face.
We already know how brain cells can tell which direction we are currently facing.
That discovery was celebrated when UCL professor John O'Keefe was awarded the 2014 Nobel Prize in Physiology or Medicine for discovering the brain's "inner GPS".
This new study adds to that discovery by revealing where our "sense of direction" comes from. It shows that the part of the brain that signals which direction we face - called the entorhinal region - also signals the direction we need to travel.
Study leader Dr. Hugo Spiers, senior lecturer in UCL's Department of Experimental Psychology, says scientists have thought for years that this type of "homing signal" exists, but until now, it was just speculation:
"Studies on London cab drivers have shown that the first thing they do when they work out a route is calculate which direction they need to head in. We now know that the entorhinal cortex is responsible for such calculations, and the quality of signals from this region seems to determine how good someone's navigational skills will be."
Strength of homing signal influenced navigation performance
For the study, Dr. Spiers and his team invited 16 healthy volunteers to navigate a computer simulation of a simple square environment with four walls. Each wall showed a different landscape and each corner contained a different object.
The volunteers familiarized themselves with the environment using the computer simulation. Then, they were placed in a certain corner and asked to navigate to an object in another corner while the researchers recorded their brain activity using functional magnetic resonance imaging (fMRI).
Dr. Spiers says it was a simple test where they just wanted to see which areas of the brain were active as the volunteers thought about different directions.
But they were surprised, he notes, by how "the strength and consistency of brain signals from the entorhinal region noticeably influenced people's performance in such a basic task."
"We now need to investigate the effect in more complex navigational tasks, but I would expect the differences in entorhinal activity to have a larger impact on more complex tasks," he adds.
Lead author Dr. Martin Chadwick, also of UCL's Experimental Psychology department, says the study supports the idea that our "internal compass" updates itself as we move through our environment:
"For example, if you turn left, then your entorhinal region should process this to shift your facing direction and goal direction accordingly. If you get lost after taking too many turns, this may be because your brain could not keep up and failed to adjust your facing and goal directions."
In further tests, the team found that the entorhinal region references what they called "geocentric" information - that is, the internal compass uses the external environment as its reference point and not the body's axis.
The entorhinal region is one of the first areas of the brain affected by Alzheimer's disease, so the study may explain why getting lost and confused about direction is an early symptom.
The team hopes to develop the computer simulation so it can be used as a simple aid to diagnosing and monitoring the disease.
The study was funded by the Wellcome Trust.