Intact spatial updating during locomotion after right posterior parietal lesions

Beyond small-scale spatial skills: Navigation skills and geoscience education

Background

Research examining the relation between spatial skills and the science, technology, engineering and mathematics (STEM) fields has focused on small-scale spatial skills, even though some STEM disciplines—particularly the geography and geoscience (GEO) fields—involve large-scale spatial thinking at the core of their professional training. In Study 1, we compared large-scale navigation skills of experienced geologists with those of experienced psychologists, using a novel virtual navigation paradigm as an objective measure of navigation skills. In Study 2, we conducted a longitudinal study with novice Geographic Information Systems (GIS) students to investigate baseline navigational competence and improvement over the course of an academic semester.

Results

In Study 1, we found that geologists demonstrated higher navigational competence and were more likely to be categorized as integrating separate routes, compared to their non-STEM counterparts. In Study 2, novice GIS students showed superior baseline navigational competence compared to non-STEM students, as well as better spatial working memory and small-scale mental rotation skills, indicating self-selection. In addition, GIS students’ spatial skills improved more over the course of a semester than those of non-STEM students.

Conclusions

Our findings highlight the importance of large-scale spatial thinking for enrollment and success in the GEO fields but likely also across the broader range of thinking involving spatial distributions. We discuss the potential of GIS tools to develop spatial skills at an early age.

Memory for Object Location in Augmented Reality: The Role of Gender and the Relationship Among Spatial and Anxiety Outcomes

The potential of augmented reality (AR) technology for the study of spatial memory and orientation is a new research field. AR defines systems that attempt to enhance the user’s experience with the physical world. In our app, we enhance the sense of sight by adding interactive 3D elements to the real environment. Our app can be used in any real environment so that the experimental conditions during the tasks and the way in which an individual navigates are similar to those used in real life. With AR, the experimenter has a high level of control of the task and can store the participant’s responses accurately. The classical factors that influence an individual’s performance on virtual spatial tasks are gender and cognitive factors. The influence of emotional factors on spatial performance has been studied more recently. Since AR tasks for the study of spatial memory and spatial orientation are new developments, little is known about the factors that are related to performance on tasks of this type. In our study, we tested 46 young adults (26 women) in an AR object-location task that was performed in a building. The participants had to memorize the position of eight virtual objects while they were walking through the environment. We also assessed the participants’ performance on an object-recall task, a map-pointing task, and a paper-and-pencil spatial orientation task. The self-reported importance of different spatial strategies for wayfinding and the levels of trait anxiety and wayfinding anxiety were also evaluated. Our findings indicate that men performed better on the spatial paper-and-pencil test and spent more time completing the learning phase of the AR task. The spatial memory for the location of the objects in AR and on the map correlated positively. Anxiety was related to individual differences in the self-reported use of a spatial orientation strategy, but the association among them was weak. Trait anxiety was positively related to the time employed by the participants during the learning phase of the AR task, whereas wayfinding anxiety correlated negatively with the preference for an orientation strategy. Our results highlight the importance of anxiety in spatial orientation.

Real-space path integration is impaired in Alzheimer's disease and mild cognitive impairment

INTRODUCTION

Path integration (PI) is an important component of spatial navigation that integrates self-motion cues to allow the subject to return to a starting point. PI depends on the structures affected early in the course of Alzheimer's disease (AD) such as the medial temporal lobe and the parietal cortex.

OBJECTIVES

To assess whether PI is impaired in patients with mild AD and amnestic mild cognitive impairment (aMCI) and to investigate the role of the hippocampus, entorhinal and inferior parietal cortex in this association.

METHODS

27 patients with aMCI, 14 with mild AD and 18 controls completed eight trials of Arena Path Integration Task. The task required subjects with a mask covering their eyes to follow an enclosed triangle pathway through two previously seen places: start-place1-place2-start. Brains were scanned at 1.5T MRI and respective volumes and thicknesses were derived using FreeSurfer algorithm.

RESULTS

Controlling for age, education, gender and Mini-Mental State Examination score the aMCI and AD subjects were impaired in PI accuracy on the pathway endpoint (p=0.042 and p=0.013) compared to controls. Hippocampal volume and thickness of entorhinal and parietal cortices explained separately 36-45% of the differences in PI accuracy between controls and aMCI and 28-31% of the differences between controls and AD subjects.

CONCLUSIONS

PI is affected in aMCI and AD, possibly as a function of neurodegeneration in the medial temporal lobe structures and the parietal cortex. PI assessment (as a part of spatial navigation testing) may be useful for identification of patients with incipient AD.

Perception and action

The phrase perception and action is used widely but in diverse ways in the context of the relationship between perceptual and motor processes. This review describes and integrates five perspectives on perception and action which rely on both neurophysiological and behavioral levels of analysis. The two visual systems view proposes dissociable but interactive systems for conscious processing of objects/space and the visual control of action. The integrative view proposes tightly calibrated but flexible systems for perception and motor control in spatial representation. The embodied view posits that action underlies perception, involving common coding or motor simulation systems, and examines the relationship between action observation, imitation, and the understanding of intention. The ecological view emphasizes environmental information and affordances in perception. The functional view defines the relationship between perception, action planning, and semantics in goal-directed actions. Although some of these views/approaches differ in significant ways, their shared emphasis on the importance of action in perception serves as a useful unifying framework. WIREs Cogn Sci 2010 1 800-810 For further resources related to this article, please visit the WIREs website.

Medial temporal lobe roles in human path integration

Path integration is a process in which observers derive their location by integrating self-motion signals along their locomotion trajectory. Although the medial temporal lobe (MTL) is thought to take part in path integration, the scope of its role for path integration remains unclear. To address this issue, we administered a variety of tasks involving path integration and other related processes to a group of neurosurgical patients whose MTL was unilaterally resected as therapy for epilepsy. These patients were unimpaired relative to neurologically intact controls in many tasks that required integration of various kinds of sensory self-motion information. However, the same patients (especially those who had lesions in the right hemisphere) walked farther than the controls when attempting to walk without vision to a previewed target. Importantly, this task was unique in our test battery in that it allowed participants to form a mental representation of the target location and anticipate their upcoming walking trajectory before they began moving. Thus, these results put forth a new idea that the role of MTL structures for human path integration may stem from their participation in predicting the consequences of one's locomotor actions. The strengths of this new theoretical viewpoint are discussed.

Revisiting the effect of quality of graphics on distance judgments in virtual environments: a comparison of verbal reports and blind walking

In immersive virtual environments, judgments of perceived egocentric distance are significantly underestimated, as compared with accurate performance in the real world. Two experiments assessed the influence of graphics quality on two distinct estimates of distance, a visually directed walking task and verbal reports. Experiment 1 demonstrated a similar underestimation of distances walked to previously viewed targets in both low- and high-quality virtual classrooms. In Experiment 2, participants' verbal judgments underestimated target distances in both graphics quality environments but were more accurate in the high-quality environment, consistent with the subjective impression that high-quality environments seem larger. Contrary to previous results, we suggest that quality of graphics does influence judgments of distance, but only for verbal reports. This behavioral dissociation has implications beyond the context of virtual environments and may reflect a differential use of cues and context for verbal reports and visually directed walking.

Spatial updating: how the brain keeps track of changing object locations during observer motion

As you move through an environment, the positions of surrounding objects relative to your body constantly change. Updating these locations is a central feature of situational awareness and readiness to act. Here, we used functional magnetic resonance imaging and a virtual environment to test how the human brain uses optic flow to monitor changing object coordinates. Only activation profiles in the precuneus and the dorsal premotor cortex (PMd) were indicative of an updating process operating on a memorized egocentric map of space. A subsequent eye movement study argued against the alternative explanation that activation in PMd could be driven by oculomotor signals. Finally, introducing a verbal response mode revealed a dissociation between the two regions, with the PMd only showing updating-related responses when participants responded by pointing. We conclude that visual spatial updating relies on the construction of updated representations in the precuneus and the context-dependent planning of motor actions in PMd.

Aging and path integration skill: kinesthetic and vestibular contributions to wayfinding

In a triangle completion task designed to assess path integration skill, younger and older adults performed similarly after being led, while blindfolded, along the route segments on foot, which provided both kinesthetic and vestibular information about the outbound path. In contrast, older adults' performance was impaired, relative to that of younger adults, after they were conveyed, while blindfolded, along the route segments in a wheelchair, which limited them principally to vestibular information. Correlational evidence suggested that cognitive resources were significant factors in accounting for age-related decline in path integration performance.

Spatial memory following shifts of gaze. I. Saccades to memorized world-fixed and gaze-fixed targets

During a shift of gaze, an object can move along with gaze or stay fixed in the world. To examine the effect of an object's reference frame on spatial working memory, we trained monkeys to memorize locations of visual stimuli as either fixed in the world or fixed to gaze. Each trial consisted of an initial reference frame instruction, followed by a peripheral visual flash, a memory-period gaze shift, and finally a memory-guided saccade to the location consistent with the instructed reference frame. The memory-period gaze shift was either rapid (a saccade) or slow (smooth pursuit or whole body rotation). This design allowed a comparison of memory-guided saccade performance under various conditions. Our data indicate that after a rotation or smooth-pursuit eye movement, saccades to memorized world-fixed targets are more variable than saccades to memorized gaze-fixed targets. In contrast, memory-guided saccades to world- and gaze-fixed targets are equally variable following a visually guided saccade. Across all conditions, accuracy, latency, and main sequence characteristics of memory-guided saccades are not influenced by the target's reference frame. Memory-guided saccades are, however, more accurate after fast compared with slow gaze shifts. These results are most consistent with an eye-centered representational system for storing the spatial locations of memorized objects but suggest that the visual system may engage different mechanisms to update the stored signal depending on how gaze is shifted.

On selective left neglect during walking in a child

In this article we describe a child affected by right parieto-occipital lesion due to head injury. The patient showed left hemianopia, but not unilateral spatial neglect on traditional paper-and-pencil tests and on "ecological" tests. However, his parents reported frequent collisions with obstacles on the left side. A specific test was set up: The patient had to kick down skittles put on both sides of a route traced on the floor. He kicked down 89% of skittles on the right, but only 38% on the left side. These findings are discussed in light of recent theories on unilateral neglect.

Updating of locations during whole-body rotations in patients with hemispatial neglect

Posterior parietal cortex lesions have been associated with both hemispatial neglect and spatial-updating deficits. Currently, the relation between these processes remains poorly understood. We tested the ability of parietal patients with neglect to update remembered target locations during passive whole-body rotations. The rotations and manual pointing responses were executed with and without vision. During the rotation, the remembered location stayed on the same side of the body midline or crossed the midline. Parietal patients generally underestimated rotations, as compared with control groups, but updated targets equally well on either side of the body midline, regardless of the amount of updating required. Once parietal patients have localized a target, they can use self-motion information to update its location, even if it passes into the region they typically neglect. This lack of contralesional updating effects contrasts with impairments in eye position updating found in previous work with parietal patients.