Measuring changes in how humans find their way could enable earlier diagnosis of dementia in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) or Alzheimer’s disease, a new review study suggests.
The influence of aging on how humans map their surroundings, and visualize and choose different routes to get from one place to another, has remained unexplored, compared to the alterations induced by memory and learning. However, researchers believe that the decline in navigational ability could aid earlier diagnosis of dementia.
“In humans, navigation is much more cumbersome to research than learning or memory,” Thomas Wolbers, lead author of the study, said in a press release. Wolbers is the Laboratory Head of the Aging & Cognition Research Group at the German Center for Neurodegenerative Diseases, in Magdeburg, Germany. “But it has such a dramatic impact on everyday life, and the key structures of the ‘navigational network’ in the brain are very sensitive to both ordinary healthy aging and pathological factors.”
As humans age, the strategies to chart directions alter. Healthy, older individuals prefer to map landmarks or boundaries relative to their body position (an egocentric strategy). This contrasts with the allocentric strategy, done in relation to external objects, which enables much more efficient learning of the spatial layout. Of note, the egocentric approach can lead to reduced mobility, which is a worrisome sign in younger people.
Current Alzheimer’s disease diagnosis is based on an individual’s medical history, genetic risk factors, and performance on cognitive tests that assess memory, language, and reasoning. Importantly, the research team indicates that navigational dysfunction is among the earliest symptoms of the disease. Likewise, a comprehensive, neuropsychological evaluation is warranted in ALS to assess cognitive and behavioral impairments.
“It can take up to 10 years after the onset of [Alzeimer’s disease] for someone to show abnormal results on the standard cognitive tests that are available today, and that’s 10 years that you’ve lost for treating it,” Wolbers said. “This is where navigation-based diagnostics could contribute, by reducing that window.”
In order to reliably test navigational ability, researchers still need consistent standard tests. One promising path toward that goal is the development of less expensive and portable virtual reality technology. The study’s co-author Jan Wiener, PhD, from Bournemouth University in the United Kingdom, is involved in the creation of a mobile app to gather population data on navigation decisions to help the study of dementia.
Another obstacle that needs to be addressed is the variability in navigational behaviors from person to person, which is greater than in memory or other cognitive functions, Wolbers observed. An effective diagnosis may require tracking an individual’s navigation ability throughout life, in search of signs of early or accelerated alterations.
“We need longitudinal human data to be able to definitively say whether a change in navigational function can be used to predict whether [Alzheimer’s disease] or any other neurodegenerative disease will develop later on,” Wolbers said.
Overall, these improvements may enable the creation of a navigational battery of tests similar to those used for memory and learning. For now, people should train their own navigational skills, instead of relying too much on technology such as GPS, as “it can have a detrimental effect on your navigational ability and in the long term may even be a risk to develop pathological conditions,” Wolbers said.
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