At a certain point, each person on this planet must figuratively find their own path in this life. Of course, it’s also helpful to be able to navigate one’s way in a literal sense as well.
Some people naturally have a better sense of direction than others, but a new study finds frequent spatial navigation problems are often observed in adults at a greater genetic risk of developing Alzheimer’s later in life. It’s well established that Alzheimer’s patients suffer from disorientation and can become lost in the simplest of pathways, but this is the first research to suggest that navigation problems appear years before any other symptoms.
Spatial navigating, broadly speaking, means one’s ability to remember and move through different environments. Now, a key element of human (and animal) spatial navigation is path integration.
Path integration refers to our ability to keep track of our location in reference to the surrounding environment in the absence of visual cues. So, say you were to close your eyes right now and attempt to make your way to the closest bathroom. Chances are you would have a pretty good idea of what moves you’ll have to make to get to the toilet. That’s path integration.
“If you get up at night and want to find your way to the bathroom in the dark, you need – in addition to knowing the arrangement of your own home – a mechanism that tracks your own position in the room without using external cues,” explains lead study author Anne Bierbrauer in a university release.
An essential aspect of this study was the research team’s working assumption that grid cells located in the brain’s entorhinal cortex are responsible for each individual’s path integration skills. Why did they make this assumption? In past experiments, these grid cells have displayed a “unique activity pattern” while participants navigated a spatial environment. Moreover, scientists have long agreed that the entorhinal cortex facilitates spatial navigating in general.
The entorhinal cortex has also been shown to be one of the first brain regions, in general, to be affected by Alzheimer’s.
In addition to all that, the researchers had also already conducted an earlier study that discovered the aforementioned grid cells function differently in people at genetic risk of Alzheimer’s. However, that study didn’t find any evidence that those individuals were dealing with any navigation problems.
“We assume that they used compensatory mechanisms to find their way,” notes study co-author Nikolai Axmacher, “presumably via external cues in their surroundings. In Bochum, for example, the winding tower of the Bergbau-Museum can be seen in many places, as it is often visible over the rooftops of other buildings.”
So, this time around, to do away with any helpful towers or other large buildings, the study’s authors created a “computerized navigation task” for participants. All in all, the navigational skills of 202 adults with no signs of a genetic predisposition for Alzheimer’s were compared to the performance of 65 others with a confirmed genetic risk for dementia.
Overwhelmingly, participants at genetic risk of Alzheimer’s performed worse on the digital navigation task than other study subjects.
“In this study, we demonstrated a very specific deficit in healthy people with a genetically increased risk for Alzheimer’s,” concludes study co-author Lukas Kunz. “In the future, such behavioural changes might perhaps help diagnose Alzheimer’s disease earlier, before any serious symptoms appear.”
Alzheimer’s is a terrifying condition, and it’s tough for anyone to hear they may develop the disease at a later date. On the other side of that coin, though, is the fact that earlier detection may go an incredibly long way toward improving the effectiveness of drug therapies and other dementia interventions.
It’s also worth mentioning that a second experiment was conducted with a new group of participants, this time with each subject wearing a device that recorded their brain activity. This round of testing confirmed researchers’ initial assumption regarding grid cells in the entorhinal cortex. These cells are indeed linked to the ability to move around efficiently without visual cues.
The full study can be found here, published in Science Advances.