Alzheimer's Symptoms: Navigational Skills May Deteriorate Long Before Memory
Typically, when we think of the early signs of Alzheimer’s disease we think of memory problems. Words go missing, names escape one's grasp, daily tasks are forgotten. Now, researchers at Washington University in St. Louis have shown that making mental maps of where we have been and where we are going is a process the brain may lose before memory problems begin to show. People with these early symptoms can no longer navigate even a familiar area as they once did.
“These findings suggest that navigational tasks designed to assess a cognitive mapping strategy could represent a powerful new tool for detecting the very earliest Alzheimer’s disease-related changes in cognition,” senior author Denise Head, associate professor of Psychological and Brain Sciences, noted in an interview published in the Journal of Alzheimer’s Disease.
How the study was conducted
The study used computer programs to test 71 participants. Results showed that mapping deficits can occur when there has been damage to several areas of the brain -- specifically, deterioration and shrinkage in the brain’s prefrontal cortex, hippocampus, and caudate. This experiment was designed knowing that people tend to navigate using two different forms of spatial representation and navigation.
While these deficits have been long recognized in people with early-stage Alzheimer’s, people without Alzheimer’s symptoms hadn’t been studied in depth for this problem. If the results of the study are supported in larger studies, people who show a deficit in this area -- but who have no other symptoms related to Alzheimer’s -- will be assigned the status of pre-clinical Alzheimer’s.
For this small study, participants were tested on how well they could learn and follow a pre-set route and how well they could form and use a cognitive map of the environment.
The researchers found that “people with cerebrospinal markers for preclinical Alzheimer’s disease demonstrated significant difficulties only when they had to form a cognitive map of the environment... This same preclinical Alzheimer’s disease group showed little or no impairment on route learning tasks."
_ “As the disease progresses, cognitive mapping deficits worsen, the caudate becomes involved, and route learning deficits emerge.”_
— Samantha Allison, a psychology doctoral student at Washington University
When compared with cognitively normal study participants who lacked the cerebrospinal fluid markers of Alzheimer’s, those with preclinical Alzheimer’s disease scored lower on their ability to learn the locations of objects in the environment in relation to each other during the initial study phase.
The researchers stressed that while the results of their study suggest deficits in the ability to form a cognitive map, these same preclinical Alzheimer’s disease participants “eventually managed to overcome these map-learning deficits, performing almost as well as cognitively normal participants during a subsequent wayfinding navigation task.”
In other words, while the people who exhibited a deficit during testing had more trouble learning the environmental information, with more training they were able to retain what they learned nearly as well as those who exhibited no deficit.
The researchers emphasize that this was a small study and that they didn’t have “direct information about brain regions and networks that have a role in spatial navigation and wayfinding.”
The study was supported by grants from the National Institutes of Health and the National Institute on Aging.
The value of the study rests on the fact that the researchers can now move forward to see if larger studies will show value in testing people for navigational skills to learn if they may be developing pre-clinical dementia. Most likely, this sort of testing isn’t going to be practical for the general public; however, people who have relatives with Alzheimer’s disease may want to know earlier on if they themselves might be at risk.
As with most studies, time will tell how reliable this test is. In the meantime, don’t become anxious if you sometimes have problems remembering a route when out driving or deciding the best way to drive to a new location. An important way to stay healthy is to lower stress levels. In my opinion, one way to lower stress levels is to take the studies for what they are: additional information that may or may not end up being important to your future.
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