Alzheimer’s Disease (AD) is a disease that starts to alter and damage the brain years or even decades before symptoms in a person appear. Being able to identify early if a person is at risk of having this disease would be of great help for the person, as he or she can prepare for the disease, and probably prevent it.
Scientists at the University of California San Diego School of Medicine, in a new study recently published online in the Neurobiology of Aging, state that, with further developments, measuring how fast an individual’s eyes dilate while he or she takes a cognitive test might be a “low-cost, low-invasive method” that can help in screening individuals at increased genetic risk for Alzheimer’s Disease, even before the cognitive decline begins.
In recent years, researchers investigating the pathology of AD have primarily directed their attention at two causative or contributory factors: the accumulation of protein plaques in the brain called amyloid-beta and tangles of a protein called tau. Both have been linked to damaging and killing neurons, resulting in progressive cognitive dysfunction.
The new study focuses on pupillary responses which are driven by the locus coeruleus (LC), a cluster of neurons in the brainstem involved in regulating arousal and also modulating cognitive function. Tau is the earliest occurring known biomarker for AD; it first appears in the LC; and it is more strongly associated with cognition than amyloid-beta…
The LC drives pupillary response — the changing diameter of the eyes’ pupils — during cognitive tasks. (Pupils get bigger the more difficult the brain task.) In previously published work, the researchers had reported that adults with mild cognitive impairment, often a precursor to AD, displayed greater pupil dilation and cognitive effort than cognitively normal individuals, even if both groups produced equivalent results. Critically, in the latest paper, the scientists link pupillary dilation responses with identified AD risk genes.
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