Oculomotor indicators of cognitive performance are modulated by neurodegeneration

In this study, the extent to which eye movements can be used to estimate cognitive ability in neurologically intact individuals was evaluated in the absence of clear underlying neurodegenerative processes. In contrast to previous studies of Parkinson's Disease (PD) and multiple sclerosis that demonstrated a strong link between oculomotor parameters and clinical measures of cognition, this relationship is unaffected by disease in healthy participants, enabling a more direct assessment of the connection between eye movements and cognition. Accordingly, a modest portion (≤28%) of the observed variance in cognitive test scores could be explained by oculomotor parameters in 204 participants aged 18-79 with no differences between males and females observed. The relationship between oculomotor parameters and cognitive measures was further compared between neurologically intact individuals and a separate sample of 65 individuals with PD. Oculomotor parameters showed stronger correlations with cognitive measures in PD patients, likely contributing to the greater explanatory power of oculomotor-based models in this population. Finally, given that many oculomotor parameters are affected by age, the ability to estimate an individual's age without confounding neurodegeneration was assessed. As 33% of the variance in participants' age could be explained by oculomotor parameters, age may be estimated from oculomotor parameters, providing insight into the aging brain. Collectively, these findings highlight the connection between oculomotor function and clinical measures of cognition in the absence of neurodegeneration and indicate that these relationships are likely mediated by the functional integrity of brain networks involved in both motor control and cognitive processing.