Spatial encoding of hidden objects in dogs (Canis familiaris).

The authors investigated the type of spatial information that controls domestic dogs' (Canis familiaris) search behavior in a situation in which they have to locate a spatial position where they saw an object move and disappear. In Experiments 1 and 2, the authors manipulated all local and global sources of allocentric spatial information surrounding the hiding location. The results revealed that dogs relied on an egocentric frame of reference. Experiment 3 showed that dogs also encoded allocentric information when egocentric information was irrelevant. The authors conclude that dogs simultaneously encode both egocentric and allocentric spatial information to locate a spatial position, but they primarily base their search behavior on an egocentric frame of reference. The authors discuss under which natural conditions dogs might use these 2 sources of spatial information and detail the nature of spatial egocentric information and the circumstances underlying its use by dogs. (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)     

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)     

Evidence from visuomotor adaptation for two partially independent visuomotor systems.

Visual information can specify spatial layout with respect to the observer (egocentric) or with respect to an external frame of reference (allocentric). People can use both of these types of visual spatial information to guide their hands. The question arises if movements based on egocentric and movements based on allocentric visual information comprise 2 independent visuomotor systems. In the experiments reported here, we used visuomotor adaptation to address this question. In an adaptation phase, subjects received distorted-visual feedback about their hand movements (17° rotation and 110% amplitude stretch). In a testing phase (no-visual feedback), we measured how behavior changes in response to the distorted-visual feedback. During adaptation and testing, we used 2 tasks that required processing of either egocentric or allocentric visual information. The results show that behavioral changes are significantly larger when the same task is used during testing and adaptation, compared to when the task is switched. The findings suggest that the human brain employs 2 partially independent visuomotor systems that rely on different types of visual spatial information. (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)     

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)     

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)     

Memory for Visuospatial Location Following Selective Hippocampal Sclerosis: The Use of Different Coordinate Systems.

This study addressed the role of the medial temporal lobe regions and, more specifically, the contribution of the human hippocampus in memory for body-centered (egocentric) and environment-centered (allocentric) spatial location. Twenty-one patients with unilateral atrophy of the hippocampus secondary to long-standing epilepsy (left, n = 7; right, n = 14) and 15 normal control participants underwent 3 tasks measuring recall of egocentric or allocentric spatial location. Patients with left hippocampal sclerosis were consistently impaired in the allocentric conditions of all 3 tasks but not in the egocentric conditions. Patients with right hippocampal sclerosis were impaired to a lesser extent and in only 2 of the 3 tasks. It was concluded that hippocampal structures are crucial for allocentric, but not egocentric, spatial memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Double dissociation of egocentric and allocentric space following medial prefrontal and parietal cortex lesions in the rat.

Animals with medial prefrontal cortex or parietal cortex lesions and sham-operated and non-operated controls were tested for the acquisition of an adjacent arm task that accentuated the importance of egocentric spatial lateralization and a cheese board task that accentuated the importance of allocentric spatial localization. Results indicated that relative to controls, animals with medial prefrontal cortex lesions are impaired on the adjacent arm task but displayed facilitation on the cheese board task. In contrast, relative to controls, rats with parietal cortex lesions are impaired on the cheese board task but show no impairment on the adjacent arm task. The data suggest a double dissociation of function between medial prefrontal cortex and parietal cortex in terms of coding of egocentric versus allocentric spatial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions of the dorsal hippocampus or parietal cortex differentially affect spatial information processing.

The present experiments used 2 versions of a modified Hebb-Williams maze to test the role of the dorsal hippocampus (dHip) and parietal cortex (PC) in processing allocentric and egocentric space during acquisition and retention. Bilateral lesions were made to either the dHip or PC before maze testing (acquisition) or after maze testing (retention). The results indicate that lesions of the dHip impair allocentric maze acquisition, whereas lesions of the PC impair egocentric maze acquisition. During retention, lesions of the PC produced a significant impairment on both maze versions, whereas lesions of the dHip produced short-lived, transient impairments on both maze versions. These results suggest that during acquisition, the hippocampus and PC process spatial information in parallel; however, long-term retention of spatial information requires the PC with the dHIP as necessary for retrieval and/or access but not necessarily storage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of spatial discrimination deficits following frontal and parietal lesions in monkeys.

Gave 40 rhesus monkeys dorsolateral prefrontal, posterior parietal, or inferotemporal lesions. 4 additional Ss served as unoperated controls. Ss then received 2 forms of spatial discrimination training, based on body position ("egocentric" cues) and on the position of an external referent ("allocentric" cues), respectively. On the former, a place discrimination reversal, frontal Ss were impaired but not parietals. On the latter, a landmark discrimination reversal, parietal Ss were impaired but not frontals; this result was also obtained on a test involving distance discrimination without reversal. Finally, the inferotemporals but not the frontals or parietals were impaired on a nonspatial object discrimination reversal. Results suggest that the 2 modes of spatial orientation, egocentric and allocentric, are related to frontal and parietal mechanisms, respectively. (18 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial behavior in gerbils (Meriones unguiculatus).

Investigated whether adult gerbils could use an allocentric frame of reference to efficiently solve a spatial memory task. 38 male Ss were allowed to explore an arena containing an object. The external reference frame was reduced to a single visual landmark. After habituation, Ss entered the arena from a new direction. A 2nd object, identical to the 1st object, was placed symmetrically with regard to the landmark. The 2nd object was explored more than the 1st object, a result showing that the 2nd object was differentiated on the basis of location. This result suggests that, during the course of exploration, Ss had learned about the spatial features of the experimental situation. It is suggested that Ss' final discrimination performance (preference for the novel stimulus location) reflected an allocentric rather than egocentric frame of reference. (15 ref) (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)     

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)     

Extensive cytotoxic lesions of the rat retrosplenial cortex reveal consistent deficits on tasks that tax allocentric spatial memory.

Despite the connections of the retrosplenial cortex strongly suggesting a role in spatial memory, the lesion data to date have been equivocal. Whether subjects are impaired after retrosplenial lesions seems to depend on whether the lesions were aspirative or excitotoxic, with the latter failing to produce an impairment. A shortcoming of previous excitotoxic lesion studies is that they spared the most caudal part of the retrosplenial cortex. The present study thus used rats with extensive neurotoxic lesions of the retrosplenial cortex that encompassed the entire rostrocaudal extent of this region. These rats were consistently impaired on several tests that tax allocentric memory. In contrast, they were unimpaired on an egocentric discrimination task. Although the lesions did not appear to affect object recognition, clear deficits were found for an object-in-place discrimination. The present study not only demonstrates a role for the retrosplenial cortex in allocentric spatial memory, but also explains why previous excitotoxic lesions have failed to detect any deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The cerebellum in the spatial problem solving: a co-star or a guest star?

The experimental findings reviewed here indicate that the cerebellum has to be added to the regions known to be involved in the spatial learning. Cerebellar function is specifically linked to 'how to find an object' rather than 'where the object is in the space'. In the Morris water maze (MWM) hemicerebellectomized (HCbed) rats displayed a severe impairment in coping with spatial information, displaying only peripheral circling. And yet, when the MWM cue phase was prolonged, HCbed rats succeeded in acquiring some abilities to learn platform position, even in a pure place paradigm, such as finding a hidden platform with the starting points sequentially changed. Conversely, whether the searching strategy was acquired preoperatively, no exploration deficit appeared. Thus, cerebellar lesions appear to affect the procedural components of spatial function, sparing the declarative ones. When intact animals were non-spatially pre-trained and then HCbed, they exhibited an expanded scanning strategy, underlining the cerebellar involvement in procedural component acquisition. By testing HCbed rats in an active avoidance task, first without and then with a request for right/left discrimination, lesioned rats displayed severe deficits. Thus, besides a marked impairment in facing procedural components of spatial processing, cerebellar lesion provokes deficits also in right/left discrimination task. In conclusion, it is possible to propose the cerebellum as one part of a large system that includes frontal, posterior parietal, inferior temporal cortices, hippocampus and basal ganglia. These structures form an allocentric spatial system and an egocentric control system, that interlock to process the information involved in representing an object in the space.     

Viewer perspective affects central bottleneck requirements in spatial translation tasks.

A psychological refractory period (PRP) approach and the locus of slack logic were applied to examine the novel question of whether spatial translation processes can begin before the central bottleneck when effector or noneffector stimuli are processed from an egocentric (viewer-centered) perspective. In single tasks, trials requiring spatial translations were considerably slower than trials without translations (Experiment 1). Dual tasks consisted of tone discriminations (Task 1) and spatial translations (Task 2) using PRP methods with different manipulations on perceptual and response demands. When a viewer-centered perspective was used, the effect of spatial translation was reduced at short compared with long stimulus onset asynchronies (SOAs) when the potential for code overlap between tasks was removed (Experiments 2, 3, and 4); this finding supports the view that translation processes can begin before the central bottleneck. When an allocentric (non-viewer-centered) perspective was used (Experiment 5), the slowing associated with spatial translation was additive with SOA, suggesting that the processes of spatial translation cannot begin before the bottleneck. These findings highlight the importance of viewer perspective on central bottleneck requirements. Findings are further discussed in relation to the dorsal-ventral model of action and perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Egocentric versus allocentric spatial coding in nine-month-old infants: Factors influencing the choice of code.

Presented 32 9-mo-old infants with a problem in which they saw an object hidden in 1 of 2 places but were prevented from searching for it until after the spatial relationship between infant and object had been changed in some way. Findings show the following: (a) Previous search experience at 1 place promoted response perseveration or egocentric spatial coding on later trials. (b) Infants were better at locating the object after they had moved than they were after the object had moved. (c) Differentiation of the covers for the 2 locations provided a more salient cue to allocentric position than differentiation of the surrounds of the 2 locations. The 2nd finding is taken as support for the hypothesis that as infants begin to crawl, they become better able to take into account their own displacements within a stable space but difficulties remain with the displacements of objects. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence of Separable Spatial Representations in a Virtual Navigation Task.

Three experiments investigated spatial orientation in a virtual navigation task. Subjects had to adjust a homing vector indicating their end position relative to the origin of the path. It was demonstrated that sparse visual flow was sufficient for accurate path integration. Moreover, subjects were found to prefer a distinct egocentric or allocentric reference frame to solve the task. "Turners" reacted as if they had taken on the new orientation during turns of the path by mentally rotating their sagittal axis (egocentric frame). "Nonturners," by contrast, tracked the new orientation without adopting it (allocentric frame). When instructed to use their nonpreferred reference frame, both groups displayed no decline in response accuracy relative to their preferred frame; even when presented with reaction formats based on either ego or allocentric coordinates, with format unpredictable on a trial, both groups responded highly accurately. These findings support the assumption of coexisting spatial representations during navigation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Haptic space processing--Allocentric and egocentric reference frames.

In this paper a haptic matching task is used to analyze haptic spatial processing. In various conditions, blindfolded participants were asked to make a test bar parallel to a reference bar. This always resulted in large but systematic deviations. It will be shown that the results can be described with a model in which an egocentric reference frame biases the participants' settings: What a participant haptically perceives as parallel is a weighted average of parallel in allocentric space and parallel in egocentric space. The basis of the egocentric reference frame is uncertain. There is strong evidence that at least a hand-centred reference frame is involved, but possibly a body-centred reference frame also plays a role. (PsycINFO Database Record (c) 2010 APA, all rights reserved)