Local spatial navigation or "steering" in patients with vestibular loss in a virtual reality environment.

BACKGROUND: Patients with vestibular loss have reduced wayfinding ability, but the association between vestibular loss and impaired steering spatial navigation is unclear. OBJECTIVE: To evaluate whether vestibular loss is associated with reduced steering navigation performance in a virtual reality (VR) environment containing obstacles. METHODS: 17 ambulatory adults with vestibular loss were age/sex-matched to healthy controls. Participants traversed a VR hallway with obstacles, and their navigation performance was compared using metrics such as collisions, time, total distance travelled, and speed in single and multivariate analysis. RESULTS: In univariate analysis there was no significant difference in collisions between vestibular patients and controls (1.84 vs. 2.24, p = 0.974). However, vestibular patients took more time, longer routes, and had lower speeds to complete the task (56.9 vs. 43.9 seconds, p < 0.001; 23.1 vs. 22.0 meters, p = 0.0312; 0.417 vs. 0.544 m/s, p < 0.001). These results were confirmed in multivariate analysis. CONCLUSIONS: This study found that patients with vestibular loss displayed slower gait speeds and traveled longer distances, though did not make more collisions, during a VR steering navigation task. Beyond the known influence of vestibular function on gait speed, vestibular loss may also contribute to less efficient steering navigation through an obstacle-laden environment, through neural mechanisms that remain to be elucidated.

Statistically Optimal Cue Integration During Human Spatial Navigation.

In 2007, Cheng and colleagues published their influential review wherein they analyzed the literature on spatial cue interaction during navigation through a Bayesian lens, and concluded that models of optimal cue integration often applied in psychophysical studies could explain cue interaction during navigation. Since then, numerous empirical investigations have been conducted to assess the degree to which human navigators are optimal when integrating multiple spatial cues during a variety of navigation-related tasks. In the current review, we discuss the literature on human cue integration during navigation that has been published since Cheng et al.'s original review. Evidence from most studies demonstrate optimal navigation behavior when humans are presented with multiple spatial cues. However, applications of optimal cue integration models vary in their underlying assumptions (e.g., uninformative priors and decision rules). Furthermore, cue integration behavior depends in part on the nature of the cues being integrated and the navigational task (e.g., homing versus non-home goal localization). We discuss the implications of these models and suggest directions for future research.

The influence of environmental geometry and spatial symmetry on spatial updating during locomotion.

Spatial updating based on self-motion cues is important to navigation in the absence of familiar landmarks. Previous studies showed that spatial updating without vision was automatic. The goal of the current study was to investigate whether ambiguous orientations indicated by visual cues affect spatial updating based on self-motion. Participants learned an object array in a rectangular room. After the objects were removed, participants maintained their actual perspective or turned 180° to face opposite walls of the room. Participants judged relative directions from imagined perspectives based on the memories of the object array. The actual and imagined perspectives were aligned or misaligned. Better performance for aligned than misaligned perspectives (sensorimotor alignment effects) was used to indicate spontaneous updating of ones' headings relative to the object array. In Experiment 1, participants turned their bodies in the middle of the room so that their distances to the walls of the room looked similar before and after turning (spatial symmetry at the turning position with the rectangular room shape). In Experiments 2-3, participants turned their bodies in a location so that the distances to the facing walls looked different before and after turning (spatial asymmetry at the turning position with the rectangular room shape). The results showed sensorimotor alignment effects in Experiments 2-3 but not in Experiment 1. These results suggest that updating self-orientation based on self-motion was cancelled by ambiguous orientations indicated by spatial symmetry at the turning position, but not cancelled by ambiguous orientations indicated by the rectangular room shape per se. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Integration of visual landmark cues in spatial memory.

Over the past two decades, much research has been conducted to investigate whether humans are optimal when integrating sensory cues during spatial memory and navigational tasks. Although this work has consistently demonstrated optimal integration of visual cues (e.g., landmarks) with body-based cues (e.g., path integration) during human navigation, little work has investigated how cues of the same sensory type are integrated in spatial memory. A few recent studies have reported mixed results, with some showing very little benefit to having access to more than one landmark, and others showing that multiple landmarks can be optimally integrated in spatial memory. In the current study, we employed a combination of immersive and non-immersive virtual reality spatial memory tasks to test adult humans' ability to integrate multiple landmark cues across six experiments. Our results showed that optimal integration of multiple landmark cues depends on the difficulty of the task, and that the presence of multiple landmarks can elicit an additional latent cue when estimating locations from a ground-level perspective, but not an aerial perspective.

Bayesian decision theory and navigation.

Spatial navigation is a complex cognitive activity that depends on perception, action, memory, reasoning, and problem-solving. Effective navigation depends on the ability to combine information from multiple spatial cues to estimate one's position and the locations of goals. Spatial cues include landmarks, and other visible features of the environment, and body-based cues generated by self-motion (vestibular, proprioceptive, and efferent information). A number of projects have investigated the extent to which visual cues and body-based cues are combined optimally according to statistical principles. Possible limitations of these investigations are that they have not accounted for navigators' prior experiences with or assumptions about the task environment and have not tested complete decision models. We examine cue combination in spatial navigation from a Bayesian perspective and present the fundamental principles of Bayesian decision theory. We show that a complete Bayesian decision model with an explicit loss function can explain a discrepancy between optimal cue weights and empirical cues weights observed by (Chen et al. Cognitive Psychology, 95, 105-144, 2017) and that the use of informative priors to represent cue bias can explain the incongruity between heading variability and heading direction observed by (Zhao and Warren 2015b, Psychological Science, 26[6], 915-924). We also discuss (Petzschner and Glasauer's , Journal of Neuroscience, 31(47), 17220-17229, 2011) use of priors to explain biases in estimates of linear displacements during visual path integration. We conclude that Bayesian decision theory offers a productive theoretical framework for investigating human spatial navigation and believe that it will lead to a deeper understanding of navigational behaviors.

Performance in Real World- and Virtual Reality-Based Spatial Navigation Tasks in Patients With Vestibular Dysfunction.

OBJECTIVE: This study evaluated whether vestibular dysfunction is associated with reduced spatial navigation performance. STUDY DESIGN: Cross-sectional study. SETTING: Otolaryngology Clinic in the Johns Hopkins Outpatient Center and an analogous virtual reality (VR) environment. PATIENTS: Eligible patients had diagnosis of unilateral or bilateral vestibular loss. Matched healthy controls were recruited at 1:1 ratio. INTERVENTIONS: The navigation task involved a route-based or place-based strategy in both real world and VR environments. MAIN OUTCOME MEASURES: Navigation performance was measured by distance travelled relative to optimal distance (i.e., path ratio) and the Judgments of Relative Direction (JRD) task, whereby participants had to recall relative angular distances between landmarks. RESULTS: The study sample included 20 patients with vestibular loss (mean age: 61 yrs, SD: 10.2 yrs) and 20 matched controls (mean age: 60 yrs, SD: 10.4 yrs). Patients with vestibular loss travelled significantly greater distance using both route-based (path ratio 1.3 vs. 1.0, p = 0.02) and place-based (path ratio 2.6 vs. 2.0, p = 0.03) strategies in the real world. Overall, participants performed worse in virtual reality compared to real world in both path ratio (2.2 vs. 1.7; p = 0.04) and JRD error (78° vs. 67°; p < 0.01). Furthermore, while controls exhibited significant positive correlations between real world and VR performance in place-based (ß = 0.75; p < 0.001) and JRD tasks (ß = 0.70; p < 0.001), patients with vestibular loss exhibited no similar correlations. CONCLUSIONS: The vestibular system appears to play a role in navigation ability during both actual and virtual navigation, suggesting a role for static vestibular signals in navigation performance.

A computational cognitive model of judgments of relative direction.

In the past several decades, considerable theoretical progress has been made in understanding the role of reference frames in the encoding and retrieval of spatial information about the environment. Many of these insights have come from participants making judgments of relative direction using their memories of spatial layouts. In this task, participants are asked to imagine standing at a given location and facing a certain direction, and to point to a target location. Although this task has been widely and productively used, a computational cognitive model of judgments of relative direction has yet to be introduced. Computational modeling of judgments of relative direction is a critical next step to formulating and testing hypotheses about the cognitive processes involved in establishing and using spatial reference frames. We present an initial attempt to model judgments of relative direction and fit the model to two datasets exhibiting behavioral patterns commonly observed in the spatial memory literature. The model was able to predict many important features of these data, most notably alignment effects. We discuss directions for future modeling efforts.

A comparison of methods of assessing cue combination during navigation.

Mobile organisms make use of spatial cues to navigate effectively in the world, such as visual and self-motion cues. Over the past decade, researchers have investigated how human navigators combine spatial cues, and whether cue combination is optimal according to statistical principles, by varying the number of cues available in homing tasks. The methodological approaches employed by researchers have varied, however. One important methodological difference exists in the number of cues available to the navigator during the outbound path for single-cue trials. In some studies, navigators have access to all spatial cues on the outbound path and all but one cue is eliminated prior to execution of the return path in the single-cue conditions; in other studies, navigators only have access to one spatial cue on the outbound and return paths in the single-cue conditions. If navigators can integrate cues along the outbound path, single-cue estimates may be contaminated by the undesired cue, which will in turn affect the predictions of models of optimal cue integration. In the current experiment, we manipulated the number of cues available during the outbound path for single-cue trials, while keeping dual-cue trials constant. This variable did not affect performance in the homing task; in particular, homing performance was better in dual-cue conditions than in single-cue conditions and was statistically optimal. Both methodological approaches to measuring spatial cue integration during navigation are appropriate.

Mental representations of recently learned nested environments.

Two experiments investigated the mental representations of objects' location in a virtual nested environment. In Experiment 1, participants learned the locations of objects (buildings or related accessories) in an exterior environment and then learned the locations of objects inside one of the centrally located buildings (interior environment). Participants completed judgments of relative direction in which the imagined heading was established by pairs of objects from the interior environment and the target was one of the objects in the exterior environment. Performance was best for the imagined heading and allocentric target direction parallel to the learning heading of the exterior environment, but the effect of allocentric target direction was only significant for the imagined headings aligned with the reference axes of both environments; in addition, performance was best along the front-back egocentric axis (parallel to the imagined heading). Experiment 2 used the same learning procedure. After learning, the viewpoint was moved from the exterior environment along a smooth path into a side entrance of the building/interior environment. There participants saw the array of interior objects in the orientation consistent with their movement (correct cue), the array of objects in an orientation inconsistent with their movement (misleading cue), or no array of objects (no cue), and then pointed to objects in the exterior environment. Pointing performance was best for the correct-cue condition. Collectively the results indicated that memories of nested spaces are segregated by spatial conceptual level, and that spatial relations between levels are specified in terms of the dominant reference directions.

Manipulating the visibility of barriers to improve spatial navigation efficiency and cognitive mapping.

Previous studies from psychology, neuroscience and geography showed that environmental barriers fragment the representation of the environment, reduce spatial navigation efficiency, distort distance estimation and make spatial updating difficult. Despite these negative effects, limited research has examined how to overcome barriers and if individual differences mediate their causes and potential interventions. We hypothesize that the reduced visibility caused by barriers plays a major role in accumulating error in spatial updating and encoding spatial relationships. We tested this using virtual navigation to grant participants 'X-ray' vision during environment encoding (i.e., barriers become translucent) and quantifying cognitive mapping benefits of counteracting fragmented visibility. We found that compared to the participants trained with naturalistic environment visibility, participants trained in the translucent environment had better performance in wayfinding and pointing tasks, which are theorized to measure navigation efficiency and cognitive mapping. Interestingly, these benefits were only observed in participants with high self-report sense of direction. Together, our results provide important insight into (1) how perceptual barrier effects manifest, even when physical fragmentation of space is held constant, (2) establish a novel intervention that can improve spatial learning, and (3) provide evidence that individual differences modulate perceptual barrier effects and the efficacy of such interventions.

Acquisition and transfer of spatial knowledge during wayfinding.

In the current study, we investigated the ways in which the acquisition and transfer of spatial knowledge were affected by (a) the type of spatial relations predominately experienced during learning (routes determined by walkways vs. straight-line paths between locations); (b) environmental complexity; and (c) the availability of rotational body-based information. Participants learned the layout of a virtual shopping mall by repeatedly searching for target storefronts located in 1 of the buildings. We created 2 novel learning conditions to encourage participants to use either route knowledge (paths on walkways between buildings) or survey knowledge (straight-line distances and directions from storefront to storefront) to find the target, and measured the development of route and survey knowledge in both learning conditions. Environmental complexity was manipulated by varying the alignment of the buildings with the enclosure, and the visibility within space. Body-based information was manipulated by having participants perform the experiment in front of a computer monitor or using a head-mounted display. After navigation, participants pointed to various storefronts from a fixed position and orientation. Results showed that the frequently used spatial knowledge could be developed similarly across environments with different complexities, but the infrequently used spatial knowledge was less developed in the complex environment. Furthermore, rotational body-based information facilitated spatial learning under certain conditions. Our results suggest that path integration may play an important role in spatial knowledge transfer, both from route to survey knowledge (cognitive map construction), and from survey to route knowledge (using cognitive map to guide wayfinding). (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Virtual Orientation Overrides Physical Orientation to Define a Reference Frame in Spatial Updating.

Previous studies showed that people could use either an egocentric or allocentric reference frame in spatial updating with body-based cues (i.e., physical body movements), but the adopted reference frame was anchored by the physical egocentric front when body-based cues were constrained. A recent study (He et al., 2018) showed that even without body-based cues, the orientation participants initially faced in the virtual environment (VE; initial heading) could be used to establish a reference frame, suggesting that the physical egocentric front could be overridden by a virtual orientation. In the current project, we aimed to: (a) replicate He et al.'s (2018) finding; (b) examine when the reference frame defined by the virtual initial heading was established; and (c) investigate the cognitive processes in establishing the initial heading as a reference frame. In four experiments, we were able to replicate the previous findings and found that the reference frame defined by the initial heading was established during spatial updating. More importantly, the reference frame defined by the initial heading was egocentric and participants did not need to know the orientation of their initial heading at the beginning of spatial updating to be able to use it. We discuss the cognitive processes of reference frame selection in spatial updating when body-based cues are absent.

Optimal combination of environmental cues and path integration during navigation.

Navigation is influenced by body-based self-motion cues that are integrated over time, in a process known as path integration, as well as by environmental cues such as landmarks and room shape. In two experiments we explored whether humans combine path integration and environmental cues (Exp. 1: room shape; Exp. 2: room shape, single landmark, and multiple landmarks) to reduce response variability when returning to a previously visited location. Participants walked an outbound path in an immersive virtual environment before attempting to return to the path origin. Path integration and an environmental cue were both available during the outbound path, but experimental manipulations created single- and dual-cue conditions during the return path. The response variance when returning to the path origin was reduced when both cues were available, consistent with optimal integration predicted on the basis of Bayesian principles. The findings indicate that humans optimally integrate multiple spatial cues during navigation. Additionally, a large (but not a small) cue conflict caused participants to assign a higher weight to path integration than to environmental cues, despite the relatively greater precision afforded by the environmental cues.

Reference frames in spatial updating when body-based cues are absent.

The current study investigated the reference frame used in spatial updating when idiothetic cues to self-motion were minimized (desktop virtual reality). In Experiment 1, participants learned a layout of eight objects from a single perspective (learning heading) in a virtual environment. After learning, they were placed in the same virtual environment and used a keyboard to navigate to two of the learned objects (visible) before pointing to a third object (invisible). We manipulated participants' starting orientation (initial heading) and final orientation (final heading) before pointing, to examine the reference frame used in this task. We found that participants used the initial heading and the learning heading to establish reference directions. In Experiment 2, the procedure was almost the same as in Experiment 1 except that participants pointed to objects relative to an imagined heading that differed from their final heading in the virtual environment. In this case, pointing performance was only affected by alignment with the learning heading. We concluded that the initial heading played an important role in spatial updating without idiothetic cues, but the representation established at this heading was transient and affected by the interruption of spatial updating; the learning heading, on the other hand, corresponded to an enduring representation which was used consistently.

Spatial Updating Strategy Affects the Reference Frame in Path Integration.

This study investigated how spatial updating strategies affected the selection of reference frames in path integration. Participants walked an outbound path consisting of three successive waypoints in a featureless environment and then pointed to the first waypoint. We manipulated the alignment of participants' final heading at the end of the outbound path with their initial heading to examine the adopted reference frame. We assumed that the initial heading defined the principal reference direction in an allocentric reference frame. In Experiment 1, participants were instructed to use a configural updating strategy and to monitor the shape of the outbound path while they walked it. Pointing performance was best when the final heading was aligned with the initial heading, indicating the use of an allocentric reference frame. In Experiment 2, participants were instructed to use a continuous updating strategy and to keep track of the location of the first waypoint while walking the outbound path. Pointing performance was equivalent regardless of the alignment between the final and the initial headings, indicating the use of an egocentric reference frame. These results confirmed that people could employ different spatial updating strategies in path integration (Wiener, Berthoz, & Wolbers Experimental Brain Research 208(1) 61-71, 2011), and suggested that these strategies could affect the selection of the reference frame for path integration.

Where you are affects what you can easily imagine: Environmental geometry elicits sensorimotor interference in remote perspective taking.

Imagined perspective switches are notoriously difficult, a fact often ascribed to sensorimotor interference between one's to-be-imagined versus actual orientation. Here, we demonstrate similar interference effects, even if participants know they are in a remote environment with unknown spatial relation to the learning environment. Participants learned 15 target objects irregularly arranged in an office from one orientation (0°, 120°, or 240°). Participants were blindfolded and disoriented before being wheeled to a test room of similar geometry (exp.1) or different geometry (exp.2). Participants were seated facing 0, 120°, or 240°, and asked to perform judgments of relative direction (JRD, e.g., imagine facing "pen", point to "phone"). JRD performance was improved when participants' to-be-imagined orientation in the learning room was aligned with their physical orientation in the current (test) room. Conversely, misalignment led to sensorimotor interference. These concurrent reference frame facilitation/interference effects were further enhanced when the current and to-be-imagined environments were more similar. Whereas sensorimotor alignment improved absolute and relative pointing accuracy, sensorimotor misalignment predominately increased response times, supposedly due to increased cognitive demands. These sensorimotor facilitation/interference effects were sustained and could not be sufficiently explained by initial retrieval and transformation costs. We propose that facilitation/interference effects occurred between concurrent egocentric representations of the learning and test environment in working memory. Results suggest that merely being in a rectangular room might be sufficient to automatically re-anchor one's representation and thus produce orientation-specific interference. This should be considered when designing perspective-taking experiments to avoid unintended biases and concurrent reference frame alignment effects.

Cue combination in human spatial navigation.

This project investigated the ways in which visual cues and bodily cues from self-motion are combined in spatial navigation. Participants completed a homing task in an immersive virtual environment. In Experiments 1A and 1B, the reliability of visual cues and self-motion cues was manipulated independently and within-participants. Results showed that participants weighted visual cues and self-motion cues based on their relative reliability and integrated these two cue types optimally or near-optimally according to Bayesian principles under most conditions. In Experiment 2, the stability of visual cues was manipulated across trials. Results indicated that cue instability affected cue weights indirectly by influencing cue reliability. Experiment 3 was designed to mislead participants about cue reliability by providing distorted feedback on the accuracy of their performance. Participants received feedback that their performance with visual cues was better and that their performance with self-motion cues was worse than it actually was or received the inverse feedback. Positive feedback on the accuracy of performance with a given cue improved the relative precision of performance with that cue. Bayesian principles still held for the most part. Experiment 4 examined the relations among the variability of performance, rated confidence in performance, cue weights, and spatial abilities. Participants took part in the homing task over two days and rated confidence in their performance after every trial. Cue relative confidence and cue relative reliability had unique contributions to observed cue weights. The variability of performance was less stable than rated confidence over time. Participants with higher mental rotation scores performed relatively better with self-motion cues than visual cues. Across all four experiments, consistent correlations were found between observed weights assigned to cues and relative reliability of cues, demonstrating that the cue-weighting process followed Bayesian principles. Results also pointed to the important role of subjective evaluation of performance in the cue-weighting process and led to a new conceptualization of cue reliability in human spatial navigation.

Age and gender differences in spatial perspective taking.

BACKGROUND AND AIMS: It is often necessary in daily experience to change one's point of view to adopt mentally the spatial perspective of other persons, learn the position of different objects in a new environment or even describe an environment to other persons. Hence, the ability to link spatial information from different perspectives seems to be necessary to orient ourselves in the space. Several studies have found gender-related differences in spatial reasoning in younger adults, but little is known about such effects in middle-aged and older adults. METHODS: This research was designed to study how spatial perspective taking is affected by gender and age along the lifespan. The Perspective Taking/Spatial Orientation Test (PPT; Kozhevnikov and Hegarty [1]) was administered to groups of younger, middle-aged, and older adults, with females and males represented in each age group. RESULTS: The performance in the PPT decreased across age groups. All age groups had more errors in items that involved perspective changes of greater than 90º. Males performed better than females on most of the variables; however, no significant differences appeared in the interaction gender × age. CONCLUSION: The present findings showed the relevance of the degree perspective change in visuo-spatial abilities, especially in the older group. In relation with the gender, males outperformed females; however, the interaction gender × age did not show significant differences.

More than a cool illusion? Functional significance of self-motion illusion (circular vection) for perspective switches.

Self-motion can facilitate perspective switches and "automatic spatial updating" and help reduce disorientation in applications like virtual reality (VR). However, providing physical motion through moving-base motion simulators or free-space walking areas comes with high cost and technical complexity. This study provides first evidence that merely experiencing an embodied illusion of self-motion ("circular vection") can provide similar behavioral benefits as actual self-motion: Blindfolded participants were asked to imagine facing new perspectives in a well-learned room, and point to previously learned objects. Merely imagining perspective switches while stationary yielded worst performance. When perceiving illusory self-rotation to the novel perspective, however, performance improved significantly and yielded performance similar to actual rotation. Circular vection was induced by combining rotating sound fields ("auditory vection") and biomechanical vection from stepping along a carrousel-like rotating floor platter. In sum, illusory self-motion indeed facilitated perspective switches and thus spatial orientation, similar to actual self-motion, thus providing first compelling evidence of the functional significance and behavioral relevance of vection. This could ultimately enable us to complement the prevailing introspective vection measures with behavioral indicators, and guide the design for more affordable yet effective VR simulators that intelligently employ multi-modal self-motion illusions to reduce the need for costly physical observer motion.

Bias in Human Path Integration Is Predicted by Properties of Grid Cells.

Accurate wayfinding is essential to the survival of many animal species and requires the ability to maintain spatial orientation during locomotion. One of the ways that humans and other animals stay spatially oriented is through path integration, which operates by integrating self-motion cues over time, providing information about total displacement from a starting point. The neural substrate of path integration in mammals may exist in grid cells, which are found in dorsomedial entorhinal cortex and presubiculum and parasubiculum in rats. Grid cells have also been found in mice, bats, and monkeys, and signatures of grid cell activity have been observed in humans. We demonstrate that distance estimation by humans during path integration is sensitive to geometric deformations of a familiar environment and show that patterns of path integration error are predicted qualitatively by a model in which locations in the environment are represented in the brain as phases of arrays of grid cells with unique periods and decoded by the inverse mapping from phases to locations. The periods of these grid networks are assumed to expand and contract in response to expansions and contractions of a familiar environment. Biases in distance estimation occur when the periods of the encoding and decoding grids differ. Our findings explicate the way in which grid cells could function in human path integration.