The findings, if borne out in future research, might help doctors diagnose Alzheimer's long before someone shows obvious memory problems, said researchers from Washington University in St. Louis.
The study included 16 people with symptoms of early stage Alzheimer's and 13 outwardly normal people with signs of preclinical Alzheimer's in fluid from around their brain and spinal cord (cerebrospinal fluid). A control group of 42 healthy people without the cerebrospinal markers was also involved.
Preclinical Alzheimer's disease refers to brain changes that occur before symptoms develop that lead to its diagnosis.
The study participants were tested on their ability to remember how to navigate a virtual maze on a computer with a series of interconnected hallways with four wallpaper patterns and 20 landmarks. Two specific skills were assessed: how well the participants could learn and follow a pre-set route, and how well they could create and use a mental map of the maze.
The group with preclinical Alzheimer's had little or no trouble learning the pre-set route, but had significant problems in creating a mental map of the maze, according to the study.
However, the participants with preclinical Alzheimer's eventually overcame this map-learning deficit, and performed nearly as well as the control group in later testing.
"These findings suggest that navigational tasks designed to assess a [mental] mapping strategy could represent a powerful new tool for detecting the very earliest Alzheimer's disease-related changes in cognition," said study senior author Denise Head, associate professor of psychological and brain sciences.
Problems with the ability to mentally map a location are well-documented in patients with early stage Alzheimer's disease. But, they had not been studied in seemingly normal people who could be headed toward the disease, the researchers said.
The presence of cerebrospinal fluid markers for Alzheimer's disease does not mean that a person is destined to develop the disease, the researchers said. Nor does difficulty finding your way around new neighborhoods.
"Future research should examine whether cognitive mapping deficits in individuals in preclinical Alzheimer's are associated with an increased risk of developing symptomatic Alzheimer's," the researchers concluded.
Results of the study were published in the April issue of the Journal of Alzheimer's Disease.
The American Academy of Family Physicians has more on Alzheimer's disease.
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