Use of self-to-object and object-to-object spatial relations in locomotion.

In 8 experiments, the authors examined the use of representations of self-to-object or object-to-object spatial relations during locomotion. Participants learned geometrically regular or irregular layouts of objects while standing at the edge or in the middle and then pointed to objects while blindfolded in 3 conditions: before turning (baseline), after rotating 240° (updating), and after disorientation (disorientation). The internal consistency of pointing in the disorientation condition was equivalent to that in the updating condition when participants learned the regular layout. The internal consistency of pointing was disrupted by disorientation when participants learned the irregular layout. However, when participants who learned the regular layout were instructed to use self-to-object spatial relations, the effect of disorientation on pointing consistency appeared. When participants who learned the irregular layout at the periphery of the layout were instructed to use object-to-object spatial relations, the effect of disorientation disappeared. These results suggest that people represent both self-to-object and object-to-object spatial relations and primarily use object-to-object spatial representation in a regular layout and self-to-object spatial representation in an irregular layout. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial memory during progressive disorientation.

Human spatial representations of object locations in a room-sized environment were probed for evidence that the object locations were encoded relative not just to the observer (egocentrically) but also to each other (allocentrically). Participants learned the locations of 4 objects and then were blindfolded and either (a) underwent a succession of 70° and 200° whole-body rotations or (b) were fully disoriented and then underwent a similar sequence of 70° and 200° rotations. After each rotation, participants pointed to the objects without vision. Analyses of the pointing errors suggest that as participants lost orientation, represented object directions generally "drifted" off of their true directions as an ensemble, not in random, unrelated directions. This is interpreted as evidence that object-to-object (allocentric) relationships play a large part in the human spatial updating system. However, there was also some evidence that represented object directions occasionally drifted off of their true directions independently of one another, suggesting a lack of allocentric influence. Implications regarding the interplay of egocentric and allocentric information are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Allocentric and Egocentric Updating of Spatial Memories.

In 4 experiments, the authors investigated spatial updating in a familiar environment. Participants learned locations of objects in a room, walked to the center, and turned to appropriate facing directions before making judgments of relative direction (e.g., "Imagine you are standing at X and facing Y. Point to Z.") or egocentric pointing judgments (e.g., "You are facing Y. Point to Z."). Experiments manipulated the angular difference between the learning heading and the imagined heading and the angular difference between the actual heading and the imagined heading. Pointing performance was best when the imagined heading was parallel to the learning view, even when participants were facing in other directions, and when actual and imagined headings were the same. Room geometry did not affect these results. These findings indicated that spatial reference directions in memory were not updated during locomotion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional Equivalence of Spatial Representations Derived From Vision and Language: Evidence From Allocentric Judgments.

Past research (e.g., J. M. Loomis, Y. Lippa, R. L. Klatzky, & R. G. Golledge, 2002) has indicated that spatial representations derived from spatial language can function equivalently to those derived from perception. The authors tested functional equivalence for reporting spatial relations that were not explicitly stated during learning. Participants learned a spatial layout by visual perception or spatial language and then made allocentric direction and distance judgments. Experiments 1 and 2 indicated allocentric relations could be accurately reported in all modalities, but visually perceived layouts, tested with or without vision, produced faster and less variable directional responses than language. In Experiment 3, when participants were forced to create a spatial image during learning (by spatially updating during a backward translation), functional equivalence of spatial language and visual perception was demonstrated by patterns of latency, systematic error, and variability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chunking in spatial memory.

In order to gain insight into the nature of human spatial representations, the current study examined how those representations are affected by blind rotation. Evidence was sought on the possibility that whereas certain environmental aspects may be updated independently of one another, other aspects may be grouped (or chunked) together and updated as a unit. Participants learned the locations of an array of objects around them in a room, then were blindfolded and underwent a succession of passive, whole-body rotations. After each rotation, participants pointed to remembered target locations. Targets were located more precisely relative to each other if they were (a) separated by smaller angular distances, (b) contained within the same regularly configured arrangement, or (c) corresponded to parts of a common object. A hypothesis is presented describing the roles played by egocentric and allocentric information within the spatial updating system. Results are interpreted in terms of an existing neural systems model, elaborating the model's conceptualization of how parietal (egocentric) and medial temporal (allocentric) representations interact. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Frames of Reference in Mobile Augmented Reality Displays.

In 3 experiments, the authors investigated spatial updating in augmented reality environments. Participants learned locations of virtual objects on the physical floor. They were turned to appropriate facing directions while blindfolded before making pointing judgments (e.g., "Imagine you are facing X. Point to Y"). Experiments manipulated the angular difference between the learning heading and the imagined heading and between the actual heading and the imagined heading. The effect of actual-imagined on pointing latency was observed for naive users but not for users with brief training or instructions concerning the fact that objects can move with body movements. The results indicated that naive users used an environment-stabilized reference frame to access information arrays, but with experience and instruction the nature of the representation changed from an environment stabilized to a body stabilized reference frame. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Layout geometry in encoding and retrieval of spatial memory.

Two experiments investigated whether the spatial reference directions that are used to specify objects' locations in memory can be solely determined by layout geometry. Participants studied a layout of objects from a single viewpoint while their eye movements were recorded. Subsequently, participants used memory to make judgments of relative direction (e.g., "Imagine you are standing at X, facing Y, please point to Z"). When the layout had a symmetric axis that was different from participants' viewing direction, the sequence of eye fixations on objects during learning and the preferred directions in pointing judgments were both determined by the direction of the symmetric axis. These results provide further evidence that interobject spatial relations are represented in memory with intrinsic frames of reference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Layout geometry in the selection of intrinsic frames of reference from multiple viewpoints.

Four experiments investigated the roles of layout geometry in the selection of intrinsic frames of reference in spatial memory. Participants learned the locations of objects in a room from 2 or 3 viewing perspectives. One view corresponded to the axis of bilateral symmetry of the layout, and the other view(s) was (were) nonorthogonal to the axis of bilateral symmetry. Judgments of relative direction using spatial memory were quicker for imagined headings parallel to the symmetric axis than for those parallel to the other viewing perspectives. This advantage disappeared when the symmetric axis was eliminated. Moreover, there was more consistency across participants in the selection of intrinsic axes when the layout contained an axis of bilateral symmetry than when it did not. These results indicate that the layout geometry affects the selection of intrinsic frames of reference supporting the intrinsic model of spatial memory proposed by W. Mou and T. P. McNamara (2002) and by A. L. Shelton and T. P. McNamara (2001). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial memory of domestic dogs (Canis familiaris) for hidden objects in a detour task.

Spatial memory of domestic dogs (Canis familiaris) for hidden objects was investigated via a visible displacement problem of object permanence with a detour paradigm. Experiment 1 showed that dogs were able to spontaneously locate a disappearing object in a detour situation. In Experiments 2 and 3, dead reckoning and allocentric spatial information were put in conflict. Results revealed that dogs simultaneously encoded both sources of information when they had to bypass an obstacle to locate a hidden object. Experiment 3 also revealed that, over the course of testing, dogs gradually learned to rely predominantly on allocentric cues when the detour involved several reorientations. The current study reveals that spatial memory of dogs for hidden objects in a detour task was guided by flexibility in processing spatial information. Dogs could simultaneously encode dead reckoning and allocentric information to locate a disappearing object and used them hierarchically according to the complexity of the detour they encountered in the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Body- and environmental-stabilized processing of spatial knowledge.

In 5 experiments, the authors examined the perceptual and cognitive processes used to track the locations of objects during locomotion. Participants learned locations of 9 objects on the outer part of a turntable from a single viewpoint while standing in the middle of the turntable. They subsequently pointed to objects while facing the learning heading and a new heading, using imagined headings that corresponded to their current actual body heading and the other actual heading. Participants in 4 experiments were asked to imagine that the objects moved with them as they turned and were shown or only told that the objects would move with them; in Experiment 5, participants were shown that objects could move with them but were asked to ignore this as they turned. Results showed that participants tracked object locations as though the objects moved with them when shown but not when told about the consequences of their locomotion. Once activated, this processing mode could not be suppressed by instructions. Results indicated that people process object locations in a body- or an environment-stabilized manner during locomotion, depending on the perceptual consequences of locomotion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual–spatial episodic memory in schizophrenia: A multiple systems framework.

Objective: Enhanced understanding of cognitive deficits, and the neurobiological abnormalities that mediate them, can be achieved through translational research that employs comparable experimental approaches across species. This study employed a multiple-systems framework derived from the rodent literature to investigate visual–spatial memory abilities associated with schizophrenia. Method: Using the bin task, a human analog of rodent maze tasks, everyday objects were hidden in visually identical bins. Following a 1-min filled delay, participants with schizophrenia-spectrum disorders (n = 30) and healthy community controls (n = 30) were asked to identify both the object hidden and bin used on the basis of its spatial location. Three dimensions of visual–spatial memory were contrasted: (a) memory for spatial locations versus memory for objects, (b) allocentric (viewpoint independent) versus egocentric (body-centered) spatial representations, and (c) event (working) memory versus reference memory. Results: Most pronounced was a differential deficit in memory for spatial locations under allocentric (p = .005, d = ?0.77) but not egocentric viewing conditions (p = .298, d = ?0.28) in the schizophrenia group relative to healthy controls. Similarly, schizophrenia-related spatial memory deficits were pronounced under demands for event memory (p = .004, d = ?0.77) but not reference memory (p = .171, d = ?0.33). Conclusions: These results support a heuristic of preferential deficits in hippocampal-mediated forms of memory in schizophrenia. Moreover, the task provides a useful paradigm for translational research and the pattern of deficits suggests that persons with schizophrenia may benefit from mnemonic approaches favoring egocentric representations and consistency when interacting with our visual–spatial world. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mental space travel: Damage to posterior parietal cortex prevents egocentric navigation and reexperiencing of remote spatial memories.

The ability to navigate in a familiar environment depends on both an intact mental representation of allocentric spatial information and the integrity of systems supporting complementary egocentric representations. Although the hippocampus has been implicated in learning new allocentric spatial information, converging evidence suggests that the posterior parietal cortex (PPC) might support egocentric representations. To date, however, few studies have examined long-standing egocentric representations of environments learned long ago. Here we tested 7 patients with focal lesions in PPC and 12 normal controls in remote spatial memory tasks, including 2 tasks reportedly reliant on allocentric representations (distance and proximity judgments) and 2 tasks reportedly reliant on egocentric representations (landmark sequencing and route navigation; see Rosenbaum, Ziegler, Winocur, Grady, & Moscovitch, 2004). Patients were unimpaired in distance and proximity judgments. In contrast, they all failed in route navigation, and left-lesioned patients also showed marginally impaired performance in landmark sequencing. Patients' subjective experience associated with navigation was impoverished and disembodied compared with that of the controls. These results suggest that PPC is crucial for accessing remote spatial memories within an egocentric reference frame that enables both navigation and reexperiencing. Additionally, PPC was found to be necessary to implement specific aspects of allocentric navigation with high demands on spontaneous retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lack of set size effects in spatial updating: Evidence for offline updating.

Four experiments required participants to keep track of the locations of (i.e., update) 1, 2, 3, 4, 6, 8, 10, or 15 target objects after rotating. Across all conditions, updating was unaffected by set size. Although some traditional set size effects (i.e., a linear increase of latency with memory load) were observed under some conditions, these effects were independent of the updating process. Patterns of data and participant strategies were inconsistent with the common view of spatial updating as an online process. Instead, the authors concluded that participants formed enduring, long-term memory representations of the layouts at learning that were used to reconstruct spatial information about the layouts as needed (i.e., offline updating). These results support M. Amorim, S. Glasauer, K. Corpinot, and A. Berthoz's (1997) 2-system model of spatial updating that includes both online and offline updating. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Allocentric Coding of Object-to-Object Relations in Overlearned and Novel Environments.

R. F. Wang and E. S. Spelke's (2000) finding that disorientation disrupts knowledge is consistent with egocentric but not allocentric coding of object location. The present experiments tested the hypothesis that egocentric coding may dominate early on but that once an allocentric representation is established, then target location is retrieved from it. This hypothesis predicts that disorientation will disrupt configuration knowledge in a novel environment, such as that used by Wang and Spelke, but not in an overlearned environment. Experiments 1 and 2 tested whether disorientation disrupted configuration knowledge of an overlearned environment, and Experiments 3-7 tested whether disorientation disrupted configuration knowledge of a novel, room-sized environment. In none of the experiments did disorientation disrupt configuration knowledge. Hence, in addition to showing allocentric coding of overlearned interlandmark relations, the present findings are consistent with the immediate availability of allocentric location codes in a novel, room-sized environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intrinsic frames of reference in spatial memory.

Three experiments investigated the frames of reference used in memory to represent the spatial structure of the environment. Participants learned the locations of objects in a room according to an intrinsic axis of the configuration; the axis was different from or the same as their viewing perspective. Judgments of relative direction using memory were most accurate for imagined headings parallel to the intrinsic axis, even when it differed from the viewing perspective, and there was no cost to learning the layout according to a nonegocentric axis. When the shape of the layout was bilaterally symmetric relative to the intrinsic axis of learning, novel headings orthogonal to that axis were retrieved more accurately than were other novel headings. These results indicate that spatial memories are defined with respect to intrinsic frames of reference, which are selected on the basis of egocentric experience and environmental cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human navigation that requires calculating heading vectors recruits parietal cortex in a virtual and visually sparse water maze task in fMRI.

Spatial navigation in the real-world is a complex task that involves many functions, such as landmark identification, orientation, and the calculation of heading vectors. This study uses a 2 × 2 experimental design with fMRI to isolate mnemonic and navigational processes that accompany the calculation of heading vectors. The conditions are based on a working memory version of the Morris water maze task and navigation takes place in a visually austere virtual environment. In an allocentric condition, subjects navigate around a circular arena where there is one small red square on the wall. Each trial begins with an encoding phase in which subjects locate and navigate to a visible coin. Then, in a test phase, after being randomly repositioned, they retrieve the coin when it is invisible. In a control task, there are eight distinct cues around the arena that provide direct cue-place information. Results show significant interaction effects in bilateral posterior parietal cortex, which is compatible with evidence that parietal cortex helps translating between allocentric coordinates and egocentric directions. There was also greater activation for the allocentric task in right posterior hippocampus and left retrosplenial cortex, which could be related to self-localization and orientation. The findings are also compatible with the recent proposal by Kubie and Fenton (2009) that navigation primarily depends on heading vectors between salient places. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Updating displays after imagined object and viewer rotations.

Six experiments compared spatial updating of an array after imagined rotations of the array versus viewer. Participants responded faster and made fewer errors in viewer tasks than in array tasks while positioned outside (Experiment 1) or inside (Experiment 2) the array. An apparent array advantage for updating objects rather than locations was attributable to participants imagining translations of single objects rather than rotations of the array (Experiment 3). Superior viewer performance persisted when the array was reduced to 1 object (Experiment 4); however, an object with a familiar configuration improved object performance somewhat (Experiment 5). Object performance reached near-viewer levels when rotations included haptic information for the turning object. The researchers discuss these findings in terms of the relative differences in which the human cognitive system transforms the spatial reference frames corresponding to each imagined rotation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Allocentric Versus Egocentric Spatial Memory After Unilateral Temporal Lobectomy in Humans.

Thirty patients who had undergone either a right or left unilateral temporal lobectomy (14 RTL; 16 LTL) and 16 control participants were tested on a computerized human analogue of the Morris Water Maze. The procedure was designed to compare allocentric and egocentric spatial memory. In the allocentric condition, participants searched for a target location on the screen, guided by object cues. Between trials, participants had to walk around the screen, which disrupted egocentric memory representation. In the egocentric condition, participants remained in the same position, but the object cues were shifted between searches to prevent them from using allocentric memory. Only the RTL group was impaired on the allocentric condition, and neither the LTL nor RTL group was impaired on additional tests of spatial working memory or spatial manipulation. The results support the notion that the right anterior temporal lobe stores long-term allocentric spatial memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)