In a study from Caltech and the Huntington Medical Research Institutes, scientists developed a new behavioral test to detect early risk of Alzheimer’s disease.
Before the onset of the disease, by definition, cognitively healthy people do not have behavioral symptoms—and thus it’s not possible to do traditional behavioral assessments for the disease because there are no behavioral symptoms yet.
In the current study, the team tested 40 people with an average age of 75 and all cognitively healthy, who underwent tests related to Alzheimer’s risk.
From these biological markers, individuals could be categorized as high-risk or low-risk.
The team developed a task in which a participant undergoes a so-called Stroop Paradigm test. In this common test, a person is shown a word—the name of a color—displayed in colored ink.
However, the word itself does not necessarily match the color of the printed word—for example, the word “RED” is printed in the color green.
In each iteration of the task, the participant is asked to name either the color of the word or the word itself.
Compared to naming the word itself, naming the color of the text is considered “high effort”—it is more challenging than it might seem.
In this study, the researchers also added a hidden element to the Stroop Paradigm. Right before the actual target is shown, a colorless word is flashed rapidly on the screen—so rapidly that a participant cannot detect it consciously.
The colorless word is intended to unconsciously distract the participant and measure “implicit cognition.”
In addition to conscious and intentional information gathering or “explicit cognition,” our brains have a separate system in which sensory information is digested without conscious awareness—this is known as implicit cognition.
The test showed that the people with high-risk biological factors slowed down by about 4% on the Stroop test when unconscious and inconsistent word was flashed.
This suggests that the conditions that lead to Alzheimer’s may affect implicit cognition far before conscious cognition.
Thus a test to measure implicit cognitive performance may be able to detect a high risk of developing Alzheimer’s disease without the need for invasive physical measurements.
The researchers emphasize that this test is not diagnostic yet—that is, this particular test cannot measure an individual’s risk for Alzheimer’s, but simply shows a correlation between the group of high-risk individuals and worse performance on the test when an unconscious distracting word is present.
The next steps are to combine the test with other noninvasive physical measurements, such as heart rate and other neurophysiological markers, with the goal of making it more predictive.
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The study was conducted by Shinsuke Shimojo et al and published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring.
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