Identifying the Relative Contribution of Motoric and Cognitive Engagement on Spatial Memory

Abstract

I investigated the cognitive mechanisms underlying spatial memory, with the aim of differentiating the contributions of motor engagement and decision-making. In Experiment 1, I examined whether volitional motor control or decision-making, during initial exploration of a map within virtual reality, better supported retention of routes travelled. Participants explored virtual cities under three navigation conditions that varied in terms of motor and decision-making demands. During Active navigation, participants had volitional control over their movement using hand-held controllers, allowing head and body rotation in a swivel chair, and made independent decisions about which route to take to reach a target location. During Guided navigation, participants still controlled their movement, but followed a visually guided path overlaid onto the road, eliminating the need for decisionmaking. In the Passive condition participants observed a pre-defined route without having to make any decisions or engage motorically. Following exploration of each environment, participants were asked to “re-trace their steps” using the exact route they had just traveled, from the same starting point. Route memory was significantly better following Active and Guided encoding relative to Passive, suggesting that volitional movement during navigation underlay the benefit. Notably, the complexity of the path chosen by participant at encoding did not predict accuracy of route memory. Experiment 2 assessed the necessity of motor engagement and decision-making by comparing memory benefits following two types of VR implementation: Desktop-VR, in which movement was limited to keyboard input (lower motor engagement), and Headset-VR, in which participants navigated using a steering wheel (higher motor engagement). An effect of navigation strategy emerged only in the Headset-VR group: Active and Guided navigation at encoding led to significantly better route memory relative to Passive. No significant differences emerged between Active and Guided trials, suggesting that motoric engagement, rather than decision-making, is the driver of memory performance. Interestingly, in Headset-VR, a stronger personal preference for Active exploration predicted better route memory, whereas in Desktop-VR, personal motivation predicted route memory accuracy. However, neither motivation nor preference mediated performance, indicating that these factors did not account for the effect of navigation condition on memory. If motor engagement contributes to the formation of route memories, as suggested by experiments 1 and 2, then reduced mobility in older adults may influence performance, and the components underlying it. At the same time, reliance on landmark memory to guide memory may be heightened, as landmarks provide salient external cues that could compensate for reduced motor-based encoding. To test these predictions, in Experiment 3 I examined route and landmark memory in younger and older adults as they explored virtual environments. In younger adults, both Active and Guided navigation equally enhanced memory for routes compared to Passive, replicating experiments 1 and 2. However, in older adults only Active navigation, which engaged both movement and decision-making, resulted in improved route memory. Further, landmark memory in older adults benefitted the most from Active relative to Passive and Guided navigation. Simply put, active encoding eliminated age-related deficits in route memory, suggesting that decision-making (present only in this condition) during navigation may be particularly important for supporting spatial memory in aging populations. This benefit may reflect increased recruitment of frontal lobe-based resources during active navigation, which can compensate for reductions in motor engagement. There were some differences in motivation and preference ratings across conditions in both age groups. However, these subjective measures did not emerge as significant predictors of memory performance. Overall, my findings suggest that motor engagement plays a more critical role than decision-making in enhancing subsequent route memory in younger adults, whereas conditions that require decision-making benefit memory in older adults. These findings have important implications for the design of navigational tools and cognitive interventions aimed at promoting spatial independence, particularly among older adults.