Correlates and Determinants of Eye Movements Across the Adult Lifespan

Abstract

Eye movements reflect a multitude of perceptual, cognitive and motor processes. However, it is unknown what added value an oculomotor test battery has to the study protocol of cohort studies on aging and age-related diseases. To answer this question, a better understanding of the determinants and correlates of eye movements across the adult life-span is required. I based my research on data from the Rhineland Study, which is a population-based cohort study in Bonn, Germany. The oculomotor battery in the Rhineland Study includes fixation, smooth pursuit, prosaccade and antisaccade tasks. To learn the extent to which eye movement measures can serve as markers for biological aging processes, I first examined age-related variability and sex differences in eye movement performance. The analyses revealed that age was associated with all but five antisaccade measures and blink rate during fixation. Sex differences in eye movement performance were present only in smooth pursuit velocity gain and blink rate during fixation, but they were of small size. Eye movements are also known to be altered in several diseases, including schizophrenia and Alzheimer’s disease (AD). Since both aforementioned diseases represent polygenic disorders, genetic liability can be quantified using genetic risk scores. First, I investigated whether I could provide genetic evidence for antisaccades and smooth pursuit eye movements as endophenotypes for schizophrenia by associating genetic risk scores for schizophrenia with performance in the smooth pursuit and antisaccade tasks. I found that the genetic risk scores for schizophrenia were associated with antisaccade performance, supporting the endophenotype status of antisaccades for schizophrenia. I then tested which, if any, classical cognitive tasks or eye movement outcomes are sensitive to genetic susceptibility for AD. I found that Corsi forward performance and the probability of correcting antisaccade errors may be the best candidates to capture genetic liability for AD across the adult lifespan. Lastly, I investigated whether interindividual differences in cognitive performance are reflected in the mean pupil size during a fixation task. Pupil size was correlated with interindividual differences in speed of processing and response generation, but not with working memory or global cognition. On the basis of the overall work, I conclude that eye movement tasks add value to population-based studies on aging and age-related diseases as oculomotor data are language-independent and culture-free assessments of normal age-related and pathophysiological changes in brain activity.