Changes in Naturalistic Viewing in Healthy Aging and Amnestic Mild Cognitive Impairment

Visual exploration-where the eyes move and when-is guided by prior experiences. Memory-guided viewing behavior is altered in healthy aging and is further disrupted in amnestic mild cognitive impairment (aMCI), a condition in which there is accelerated structural and functional decline of the hippocampus and associated medial temporal lobe structures (HC/MTL). Computational modeling has demonstrated the potential for rapid information flow from the HC/MTL to regions responsible for the cognitive control of eye movements, such that visual exploration behavior could be impacted in the moment and on an ongoing fashion. It was predicted here, then, that older adults and individuals with aMCI would show changes in naturalistic viewing compared to younger adults, even in the absence of any memory task. Multivariate analyses revealed that viewing for younger adults was characterized by larger saccade amplitudes and a larger area of exploration; the opposite pattern was reliably expressed by individuals with aMCI. Viewing patterns of healthy older adults were associated with shorter gaze durations. The entropy of viewing in older adults was associated with overall cognitive status, as determined by the Montreal Cognitive Assessment, highlighting the top-down influence of cognitive function on active vision. Lower scores on the memory subtest were reliably associated with a pattern of viewing characterized by fewer fixations (with longer durations), saccades, regions explored, smaller area of exploration, and lower entropy, mimicking some of the viewing features of the aMCI group and suggesting that increasing HC/MTL decline results in less exploratory viewing patterns. These findings reveal the ongoing influence of the hippocampus and its extended system on moment-to-moment naturalistic viewing.