Unique graphic characters Greebles may help in detecting signs of Alzheimer’s disease decades before symptoms become apparent, said Emily Mason, a postdoctoral associate in the Department of Neurological Surgery at the University of Louisville.
In an article published online last week in Journal of Alzheimer’s Disease, Mason said that cognitively normal people who have a genetic predisposition for Alzheimer’s disease (AD) have more difficulty distinguishing among novel figures called Greebles than individuals without genetic predisposition.
“Right now, by the time we can detect the disease, it would be very difficult to restore function because so much damage has been done to the brain,” Mason said. “We want to be able to look at really early, really subtle changes that are going on in the brain. One way we can do that is with cognitive testing that is directed at a very specific area of the brain.”
AD is characterized by the presence of beta amyloid plaques and tau neurofibrillary tangles in the brain. Tau tangles predictably develop first in the perirhinal and entorhinal cortices of the brain, areas that play a role in visual recognition and memory. Mason and her colleagues developed cognitive tests designed to detect subtle deficiencies in these cognitive functions. They hoped to determine whether changes in these functions would indicate the presence of tau tangles before they could be detected through imaging or general cognitive testing.
Working in her previous position at Vanderbilt University, Mason identified test subjects age 40-60 who were considered at-risk for AD due to having at least one biological parent diagnosed with the disease. She also tested a control group of individuals in the same age range whose immediate family history did not include AD.
The subjects completed a series of “odd-man-out” tasks in which they were shown sets of four images depicting real-world objects, human faces, scenes and Greebles in which one image was slightly different than the other three. The subjects were asked to identify the image that was different.
The at-risk and control groups performed at similar levels for the objects, faces and scenes. For the Greebles, however, the at-risk group scored lower in their ability to identify differences in the images. Individuals in the at-risk group correctly identified the distinct Greeble 78 percent of the time, whereas the control group correctly identified the odd Greeble 87 percent of the time.
Alzheimer’s disease (AD) is a progressive, irreversible neurodegenerative disease characterized by declining memory, cognition and behavior. AD is the most prevalent form of dementia, affecting an estimated 5.5 million individuals in the United States and accounting for 60 to 80 percent of dementia cases. The ability to detect the disease earlier may allow researchers to develop treatments to combat the disease.