Researchers from the University of California have found a low-cost, non-invasive method to aid in diagnosing Alzheimer’s Disease (AD) before cognitive decline begins. Given that AD begins to alter and damage the brain years, perhaps even decades, before symptoms appear, researchers hope that this technique for early recognition of the illness could help develop preventative measures to help slow down in its onset.
In a new study published in Neurobiology of Aging, scientists say that soon it may be possible to screen individuals for an increased risk of AD from measuring how quickly their pupils dilate when taking cognitive tests. Their research focuses primarily on pupillary responses by the locus coeruleus (LC), a group of neurons in the brainstem involved in the regulation of arousal and the modulation of cognitive function.
Building upon previous research identifying two factors that likely cause AD: the accumulation of protein plaques in the brain known as amyloid-beta, and clusters of protein called tau, the researchers investigated how the build-up of both substances influences the early stages of AD. As both lead to progressive cognitive dysfunction, and are known to damage and kill off neurons, the researchers were particularly interested to track any physiological changes occurring from the regions in which they develop first.
With tau first appearing in the LC, the researchers began by investigating how tau affects its function. As the LC is responsible for the pupillary response, the size of one’s pupil at a given time during cognitive tasks, they found that it may be possible to measure a build-up of tau in the LC from measuring pupil dilation. With pupils tending to get larger the more difficult the mental task at hand, the researchers found that adults with mild cognitive difficulties, a common precursor to AD, tended to demonstrate greater dilation of their pupils and cognitive effort than cognitively normal individuals, even if both groups produced the same results.
According to the study's lead author, William S. Kremen, "Given the evidence linking pupillary responses, LC and tau and the association between pupillary response and AD polygenic risk scores (an aggregate accounting of factors to determine an individual's inherited AD risk), these results are proof-of-concept that measuring pupillary response during cognitive tasks could be another screening tool to detect Alzheimer's before symptoms appear.”
University of California, San Diego: Science Daily
Kremen, William S. et al: El Sevier