The role of attention in spatial (dis)orientation of older adults.

Abstract

Human ageing is accompanied by deficits in spatial navigation abilities. These changes are widespread and affect many components of the navigation system. Such changes have profound effects on an individual’s independence as their ability to learn and find their way through novel environments diminishes. Among the widespread age-related changes are declines in landmark-based place and route learning, which are the focus of this project. The work presented in this thesis seeks to enhance our understanding of the cognitive mechanisms which contribute to declining navigation ability, with a particular emphasis on attentional processes. Two place recognition experiments confirmed age-related deficits in overall place learning ability. These deficits were particularly pronounced when recognition depended on object- location binding mechanisms to encode the spatial arrangements of landmarks, as compared to recognition from object identity alone. Analyses of eye-tracking data revealed a specific visual encoding strategy which involved linking landmarks together through sequences of eye-movements. Importantly, the use of this strategy predicted place recognition performance. Older adults were less likely to use this encoding strategy than younger adults, reflecting a difference in the underlying visual attention mechanisms which aid place learning. These experiments also revealed that perspective taking mechanisms during place recognition were not affected by cognitive ageing. Four route navigation experiments demonstrated a persistent deficit in route learning and recall. Specifically, during learning older adults are slower at learning landmark-direction associations and the sequence in which places and landmarks are encountered. We found that after a route was learned successfully, which took longer for older adults, landmark- direction memory was similar between age groups, but the age-related deficit in landmark sequence knowledge remained. We suggest that this pattern of results can be explained by the prioritisation of limited attentional resources by older adults to acquire specific types of route knowledge at the expense of others. Additional analyses showed that memory for sequences of landmarks exhibited similar serial memory patterns to those found for other sequences, such as word lists, in both younger and older adults. Eye-tracking measures from one of the route navigation studies were related to navigation performance but did not differ between age groups. This finding suggests that unlike place learning, visual attention mechanisms do not contribute to age-related differences in route navigation ability. Consistent with this result, measures of attentional engagement in the same study also revealed similar regulation of attentional resources along different portions of a route for older and younger adults. Overall, the work presented in this thesis provides evidence of both intact and degraded mechanisms which contribute to navigation ability in older adults. Our findings show that regulation of attentional engagement, the control of overt visual attention during route learning, encoding of landmark identities, and perspective-taking mechanisms are similar between younger and older adults. In contrast, visual encoding strategies during place learning differ between age-groups, as does object-location binding mechanisms. Associating directions with landmarks during route learning does show age related slowing, which is overcome with several learning attempts. Age-related decline in landmark and place sequence learning remains impaired even after a route is learned. These results improve our understanding of the cognitive mechanisms which underlie navigation impairment in ageing humans, as well as shedding light on which cognitive mechanisms can still be relied upon for successful navigation.