Abstract
Memory-related viewing behavior is diminished in older adults, and lacking in amnesic cases who have reduced integrity of the medial temporal lobe (MTL), including the hippocampus, a region involved in memory. Given the link between viewing behavior and memory, the present study investigates perturbations in eye movements as a consequence of declining MTL integrity with normal and abnormal aging. Younger adults, healthy older adults, and older adults with amnestic mild cognitive impairment (aMCI) participated in a scene viewing task in which they freely viewed images presented on the screen as their eye movements were monitored. Amnestic MCI is typically associated with volume declines in the MTL, specifically the hippocampus, and is associated with subjective and objective cognitive impairment. Therefore, this group may provide key understanding of how eye movements are perturbed due to abnormal aging. We analyzed eye movement metrics to quantify the manner and extent of scene exploration. A multivariate analysis, partial least squares (PLS), was used to test if the three groups differed on the eye movement metrics. PLS results revealed that the pattern of viewing for aMCI adults was associated with more gaze fixations, more saccades, more regions sampled, yet their effective area of exploration was limited (i.e., lower root mean square deviation), saccade amplitude was lower, and viewing entropy was higher. The opposite pattern was expressed by younger adults; older adults did not express either pattern. These results demonstrate that, even in the absence of an overt memory task, patterns of eye movements recorded during free viewing can be used to differentiate groups with varying integrity of memory-related brain regions. Such findings suggest that eye movements may reveal disturbances in the moment-to-moment formation of representations in memory.