Losing your bearings in an unfamiliar environment might be more telling than forgetting where you left your keys. A new study suggests that subtle navigation difficulties could be an early sign of Alzheimer’s disease before standard memory tests detect any decline.
Researchers tested approximately 100 older adults in a virtual reality experiment designed to challenge the brain’s built-in sense of direction.
Their findings show that people with subjective cognitive decline (SCD) – a condition in which individuals feel their memory is worsening despite normal results on clinical tests – were less accurate at orienting themselves than their healthy peers.
“People with SCD are known to be at an increased risk of developing Alzheimer’s dementia later in life,” said Prof Thomas Wolbers, one of the study’s authors.
In the experiment, participants, aged 55 to 89, donned VR headsets and walked across an empty, featureless digital plain.
Their task was to follow a floating ball along a winding path and then point back to where they had started. They then had to turn and face the original direction they had been facing at the start of their initial path.
Although everyone performed within the normal range on conventional memory and thinking tests, those with SCD consistently made larger errors in the navigation task.
“These orientation difficulties did not arise from movement dynamics, such as walking faster or looking at the ground more often while walking,” says Dr Vladislava Segen, first author of the study. “The causes of the imprecise orientation were not related to motion, but cognitive in nature.”
According to the researchers, the SCD group may have performed poorly due to a “memory leak”, whereby participants struggled to keep track of the sequence of past positions needed to update their location in real time.
The researchers believe this may stem from dysfunction in grid cells – specialised neurons that build a mental coordinate system of our surroundings.
The team hopes this kind of spatial testing could one day complement existing tools for diagnosing Alzheimer’s.
“In the long term, I also see potential for use in clinical routine, specifically in the early diagnosis of Alzheimer’s disease,” Wolbers said. “However, this technique first needs to be further tested and simplified.”
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