Route repetition and route retracing: effects of cognitive aging

Retracing a recently traveled route is a frequent navigation task when learning novel routes or exploring unfamiliar environments. In the present study we utilized virtual environments technology to investigate age-related differences in repeating and retracing a learned route. In the training phase of the experiment participants were guided along a route consisting of multiple intersections each featuring one unique landmark. In the subsequent test phase, they were guided along short sections of the route and asked to indicate overall travel direction (repetition or retracing), the direction required to continue along the route, and the next landmark they would encounter. Results demonstrate age-related deficits in all three tasks. More specifically, in contrast to younger participants, the older participants had greater problems during route retracing than during route repetition. While route repetition can be solved with egocentric response or route strategies, successfully retracing a route requires allocentric processing. The age-related deficits in route retracing are discussed in the context of impaired allocentric processing and shift from allocentric to egocentric navigation strategies as a consequence of age-related hippocampal degeneration. - See more at: http://journal.frontiersin.org/Journal/10.3389/fnagi.2012.00007/abstract#sthash.xK4Htsfy.dpu

Maladaptive bias for extrahippocampal navigation strategies in aging humans.

Efficient spatial navigation requires not only accurate spatial knowledge but also the selection of appropriate strategies. Using a novel paradigm that allowed us to distinguish between beacon, associative cue, and place strategies, we investigated the effects of cognitive aging on the selection and adoption of navigation strategies in humans. Participants were required to rejoin a previously learned route encountered from an unfamiliar direction. Successful performance required the use of an allocentric place strategy, which was increasingly observed in young participants over six experimental sessions. In contrast, older participants, who were able to recall the route when approaching intersections from the same direction as during encoding, failed to use the correct place strategy when approaching intersections from novel directions. Instead, they continuously used a beacon strategy and showed no evidence of changing their behavior across the six sessions. Given that this bias was already apparent in the first experimental session, the inability to adopt the correct place strategy is not related to an inability to switch from a firmly established response strategy to an allocentric place strategy. Rather, and in line with previous research, age-related deficits in allocentric processing result in shifts in preferred navigation strategies and an overall bias for response strategies. The specific preference for a beacon strategy is discussed in the context of a possible dissociation between beacon-based and associative-cue-based response learning in the striatum, with the latter being more sensitive to age-related changes

The use of landmark-based wayfinding strategies across the adult lifespan

Individuals can employ different landmark-based wayfinding strategies to acquire spatial knowledge and support navigation. Allocentric strategy use is associated with a cognitive representation of a learned environment that allows flexible navigation, while egocentric strategy use is associated with uni-directional knowledge that only supports accurate navigation in tasks that involve reproducing learned behaviours. While many studies have investigated strategy use during navigation, how strategy use develops during spatial learning remains under- researched. Therefore, this thesis primarily investigated the processes underlying strategy selection. Participants’ strategy preference during various navigation tasks, including a novel strategy assessment paradigm developed specifically for this research, revealed that individuals adopt the most accurate strategy available – be it allocentric or egocentric – in accordance with the demands of the concurrent navigation task. Interestingly, when allocentric knowledge was required for accurate navigation, participants initially employed a suboptimal egocentric strategy before switching to an allocentric strategy, suggesting that egocentric knowledge precedes allocentric knowledge. Finally, participants were not subject to performance-related decrements associated with the effort of switching strategies. Interestingly, during spatial learning, participants acquired spatial knowledge related to alternative strategies, and selectively encoded landmarks that were compatible with the use of multiple strategies, which may explain why switching wayfinding strategies is cognitively efficient. This thesis also investigated the effects of aging on strategy selection. Strategy preference changes across the adult lifespan, with decreasing allocentric strategy use primarily attributed to reduced hippocampal function, and impaired egocentric strategy use associated with age-related learning and memory deficits. Analysis revealed that older adults exhibited a task-independent preference for egocentric strategy use, and therefore experienced difficulty with tasks that required allocentric knowledge. However, when egocentric strategy use most efficiently supported accurate navigation, younger and older adults performed similarly, suggesting that egocentric strategy use is largely unaffected by aging. Finally, age differences in strategy preference and spatial learning were observed when the most efficient route learning strategy differed between decision points, supporting findings of increasing susceptibility to switching costs with age. In summary, young adults flexibly employ a variety of strategies to optimise navigational efficacy, while older adults' strategy choices are affected by age-related difficulties with allocentric strategy use and increased vulnerability to strategy switching costs

Differences in navigation performance and postpartal striatal volume associated with pregnancy in humans.

Pregnancy is accompanied by prolonged exposure to high estrogen levels. Animal studies have shown that estrogen influences navigation strategies and, hence, affects navigation performance. High estrogen levels are related to increased use of hippocampal-based allocentric strategies and decreased use of striatal-based egocentric strategies. In humans, associations between hormonal shifts and navigation strategies are less well studied. This study compared 30 peripartal women (mean age 28 years) to an age-matched control group on allocentric versus egocentric navigation performance (measured in the last month of pregnancy) and gray matter volume (measured within two months after delivery). None of the women had a previous pregnancy before study participation. Relative to controls, pregnant women performed less well in the egocentric condition of the navigation task, but not the allocentric condition. A whole-brain group comparison revealed smaller left striatal volume (putamen) in the peripartal women. Across the two groups, left striatal volume was associated with superior egocentric over allocentric performance. Limited by the cross-sectional study design, the findings are a first indication that human pregnancy might be accompanied by structural brain changes in navigation-related neural systems and concomitant changes in navigation strategy

Human place and response learning: navigation strategy selection, pupil size and gaze behavior.

In this study, we examined the cognitive processes and ocular behavior associated with on-going navigation strategy choice using a route learning paradigm that distinguishes between three different wayfinding strategies: an allocentric place strategy, and the egocentric associative cue and beacon response strategies. Participants approached intersections of a known route from a variety of directions, and were asked to indicate the direction in which the original route continued. Their responses in a subset of these test trials allowed the assessment of strategy choice over the course of six experimental blocks. The behavioral data revealed an initial maladaptive bias for a beacon response strategy, with shifts in favor of the optimal configuration place strategy occurring over the course of the experiment. Response time analysis suggests that the configuration strategy relied on spatial transformations applied to a viewpoint-dependent spatial representation, rather than direct access to an allocentric representation. Furthermore, pupillary measures reflected the employment of place and response strategies throughout the experiment, with increasing use of the more cognitively demanding configuration strategy associated with increases in pupil dilation. During test trials in which known intersections were approached from different directions, visual attention was directed to the landmark encoded during learning as well as the intended movement direction. Interestingly, the encoded landmark did not differ between the three navigation strategies, which is discussed in the context of initial strategy choice and the parallel acquisition of place and response knowledge