Research report
Age effects on wayfinding and route learning skills

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Abstract

While existing evidence suggests that older adults have compromised spatial navigation abilities, the effects of age on specific aspects of navigational skill are less well specified. The current study examined age effects on spatial navigation abilities considering the multiple cognitive and neural factors that contribute to successful navigation. Young and older adults completed wayfinding and route learning tasks in a virtual environment and aspects of environmental knowledge were assessed. Prefrontal, caudate and hippocampal volumes were obtained in a subset of older adults. Age differences were observed in both wayfinding and route learning. For wayfinding, there were age effects in recalling landmarks, and recognizing environmental scenes. In the route learning condition, older adults evidenced difficulty with the location, temporal order and directional information of landmarks. In both conditions, there was evidence of age-related differences in the acquisition of configural knowledge. Wayfinding was associated with the hippocampus whereas route learning was associated with the caudate nucleus. These results provide indications of specific aspects of navigational learning that may contribute to age-related declines and potential neural substrates.

Introduction

Advancing age is associated with decrements in spatial navigation skills. These age-associated limitations in navigation could potentially lead to restrictions in daily activities, resistance to new environments or difficulty in transitioning to new environments, such as nursing homes [e.g., 1]. Thus, it is important to gain a greater understanding of the nature of age-related difficulties in navigation as well as better delineate the neural substrates of these deficits.

Successful navigation involves identification and knowledge of salient environmental features, critical route events, course-maintaining actions and the temporal and spatial sequence of such events and actions. Navigation may proceed based upon the development of two somewhat distinct representations. Response learning, or learning a specific route through the environment, entails the development of an action-based representation such that the sequence of body movements associated with environmental features is represented. In contrast, in place learning a more flexible internal representation or “cognitive map” of the spatial relationships amongst landmarks in the environment is formed [2]. While a distributed network of cortical and subcortical regions contributes to successful navigation [3], [4], [5], [6], these representations have relatively distinct neural underpinnings. Response learning appears to be more dependent on the striatal system whereas place learning is primarily subserved by hippocampal circuits [2], [7], [8], [9], [10], [11], [12]. Prefrontal regions may contribute to both types of learning [13], [14], [15], [16].

Previous literature provides some indications of the nature of age-related deficits with effects observed for both types of learning. Studies involving the learning of routes indicate that older adults perform more poorly than their younger counterparts [17], [18], [19]. Younger adults also outperform older adults on tasks designed to be more reliant on place learning and thus the acquisition and use of a cognitive map [20], [21], [22], [23], [24], [25]. Rather than solely a global age-related deficit, there is also evidence that age effects are apparent on specific component processes of navigation including selecting critical rather than only salient environmental features (e.g., landmarks), temporally and spatially organizing the relevant features, landmark recall, scene recognition, landmark location identification and self-orientation [19], [26], [27], [28], [29], [30], [31], [32].

While advancing age is associated with deterioration of the neural substrates of response and place learning, such as frontostriatal and hippocampal circuits [see 33 for a review], there is only limited direct evidence of the contribution of these regions to the behavioral deficits. Structural neuroimaging investigations have linked navigational success to frontostriatal [25] and hippocampal regions [21] in older adults. Both of these investigations used a virtual Morris Water Maze task, which although associated with use of a cognitive map may also incorporate aspects of response learning [23]. Route encoding has been associated with age-related alterations in neural activity in prefrontal, caudate, parahippocampal and parietal regions whereas place learning has been associated with age-related reductions in prefrontal, hippocampal, parahippocampal, retrosplenial, and parietal regions [20], [34], [35], suggesting differential involvement of the caudate and hippocampus in response and place learning, respectively, consistent with the animal literature.

The primary goal of the current study was to characterize age effects on spatial navigation abilities taking into account the multiple components that contribute to successful navigation. Performance on tasks of wayfinding (i.e., place learning) and route learning (i.e., response learning) in a virtual reality environment and the degree to which individuals were acquiring the environmental knowledge that facilitates navigation and learning new environments and routes were examined in young and older adults. In addition, associations between structural brain volumes and navigation performance were examined in older adults with the expectation that the hippocampus would be associated with wayfinding performance and the caudate nucleus would be associated with route learning. The prefrontal cortex was also examined as it has been suggested that executive deficits may at least in part underlie age effects on navigational skills [25], aging is associated with differential declines in the prefrontal cortex [33] and animal studies suggest a potential role for the prefrontal cortex in place and response learning [13], [14], [15], [16]. Thus, we hypothesized that prefrontal cortex volume would be associated with both wayfinding and route learning in the current study.

Section snippets

Participants

Older adults were recruited from a prior unpublished study on older adults in the lab that included an MRI scan to address the question regarding the neural correlates of spatial navigation in older adults. Additional older adults were recruited from an established subject pool in the Psychology Department at Washington University and young adults were undergraduate students at Washington University for the behavioral analyses. All participants were screened using a health questionnaire for

Visuomotor expertise and experience with computers, computer games and virtual reality

Although all participants completed the visuomotor expertise task in the allotted 2 min, there were age differences in the time to completion (F(1, 44) = 6.22, p < .05). There was not an effect of gender on time to complete the visuomotor maze (F < 1). In addition, there were age-related reductions in the amount of experience with computers (F(1, 44) = 16.19, p < .001), computer games (F(1, 44) = 5.67, p < .05) and with virtual reality (F(1, 44) = 22.98, p < .001). There were no significant gender differences in

Discussion

The present investigation examined age differences in spatial navigation and the role of individual differences in neural substrates. We used experimental paradigms to separately examine wayfinding and route learning and additionally assessed specific component processes that contribute to successful performance. Results confirm an age-related deficit in these two strategies for navigating and further provide indications of specific component processes and brain regions that may contribute to

Acknowledgments

This work was supported in part by the McDonnell Center for Higher Brain functions. We thank Paul Speigel and Rachel Bock for virtual reality programming, and Dana Cooper, Jennifer Travis and Tanya Antonini for assistance with data collection.

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