Spatial memory: how egocentric and allocentric combine

Recent experiments indicate the need for revision of a model of spatial memory consisting of viewpoint-specific representations, egocentric spatial updating and a geometric module for reorientation. Instead, it appears that both egocentric and allocentric representations exist in parallel, and combine to support behavior according to the task. Current research indicates complementary roles for these representations, with increasing dependence on allocentric representations with the amount of movement between presentation and retrieval, the number of objects remembered, and the size, familiarity and intrinsic structure of the environment. Identifying the neuronal mechanisms and functional roles of each type of representation, and of their interactions, promises to provide a framework for investigation of the organization of human memory more generally.     

Voluntary head movement and allocentric perception of space

Although visual input is egocentric, at least some visual perceptions and representations are allocentric, that is, independent of the observer's vantage point or motion. Three experiments investigated the visual perception of three-dimensional object motion during voluntary and involuntary motion in human subjects. The results show that the motor command contributes to the objective perception of space: Observers are more likely to apply, consciously and unconsciously, spatial criteria relative to an allocentric frame of reference when they are executing voluntary head movements than while they are undergoing similar involuntary displacements (which lead to a more egocentric bias). Furthermore, details of the motor command are crucial to spatial vision, as allocentric bias decreases or disappears when self-motion and motor command do not match.     

Theories of spatial representations and reference frames: What can configuration errors tell us?

The issue of reference frame is central to theories of spatial representations. Various classifications have been made for different types of reference frames, along with prototypical research paradigms to distinguish between them. This article focuses on the configuration error paradigm proposed by Wang and Spelke (Cognition 77:215-250, 2000) that has been used to examine the nature of the spatial representations underlying object localization during self-movement. Three basic models of spatial memory and spatial updating are discussed, as well as the assumptions behind the configuration error paradigm, to distinguish between static representations, such as the traditional allocentric cognitive map and the egocentric snapshots, and dynamic representations, such as the egocentric updating system. Recent experimental findings are reexamined and shown to be consistent with multiple models, among which the egocentric-updating-and-reload model with an enduring egocentric component provides the simplest interpretations.     

Egocentric-updating during navigation facilitates episodic memory retrieval

Influential models suggest that spatial processing is essential for episodic memory [O’Keefe, J., & Nadel, L. (1978). The hippocampus as a cognitive map. London: Oxford University Press]. However, although several types of spatial relations exist, such as allocentric (i.e. object-to-object relations), egocentric (i.e. static object-to-self relations) or egocentric updated on navigation information (i.e. self-to-environment relations in a dynamic way), usually only allocentric representations are described as potentially subserving episodic memory [Nadel, L., & Moscovitch, M. (1998). Hippocampal contributions to cortical plasticity. Neuropharmacology, 37(4-5), 431-439]. This study proposes to confront the allocentric representation hypothesis with an egocentric updated with self-motion representation hypothesis. In the present study, we explored retrieval performance in relation to these two types of spatial processing levels during learning. Episodic remembering has been assessed through Remember responses in a recall and in a recognition task, combined with a “Remember-Know-Guess” paradigm [Gardiner, J. M. (2001). Episodic memory and autonoetic consciousness: A first-person approach. Philosophical Transactions of the Royal Society B: Biological Sciences, 356(1413), 1351-1361] to assess the autonoetic level of responses. Our results show that retrieval performance was significantly higher when encoding was performed in the egocentric-updated condition. Although egocentric updated with self-motion and allocentric representations are not mutually exclusive, these results suggest that egocentric updating processing facilitates remember responses more than allocentric processing. The results are discussed according to Burgess and colleagues’ model of episodic memory [Burgess, N., Becker, S., King, J. A., & O’Keefe, J. (2001). Memory for events and their spatial context: models and experiments. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 356(1413), 1493-1503].     

听障和听力正常人群空间主导性和空间参照框架的交互作用

通过要求被试分别在近处空间和远处空间完成空间参照框架的判断任务, 考察了听障和听力正常人群空间主导性和空间参照框架的交互作用。结果表明：(1)相对于听力正常人群, 听障人群完成自我参照框架判断任务的反应时更长, 而在完成环境参照框架判断任务无显著差异; (2)听障人群和听力正常人群空间主导性和空间参照框架交互作用呈现出相反模式。研究表明, 听障人群在听力功能受损后, 其空间主导性和空间参照框架的交互作用也产生了变化。     

Spatial recall improved by retrieval enactment

Evidence from studies of intentional learning suggests that the accuracy of recall is not assisted by appropriate enactment at retrieval, as opposed to encoding. In the present study, long-term recall of spatial arrays following incidental learning (text messaging or calculator use) was tested under three different motor conditions at retrieval. For both letter and number arrays, the accuracy of recall was found to be improved by relevant enactment at the time of retrieval, relative to retrieval with no movement. In contrast, irrelevant movement was found to produce an impairment in accuracy. The overall accuracy of recalling a letter array was found to be a power-law function of the frequency of exposure to the array. The findings are discussed in terms of the hypothesis that appropriate movement during memory retrieval recruits egocentric representations that supplement allocentric representations subserving longer term spatial recall.     

Egocentric metric representations in peripersonal space: A bridge between motor resources and spatial memory

Research on visuospatial memory has shown that egocentric (subject-to-object) and allocentric (object-to-object) reference frames are connected to categorical (non-metric) and coordinate (metric) spatial relations, and that motor resources are recruited especially when processing spatial information in peripersonal (within arm reaching) than extrapersonal (outside arm reaching) space. In order to perform our daily-life activities, these spatial components cooperate along a continuum from recognition-related (e.g., recognizing stimuli) to action-related (e.g., reaching stimuli) purposes. Therefore, it is possible that some types of spatial representations rely more on action/motor processes than others. Here, we explored the role of motor resources in the combinations of these visuospatial memory components. A motor interference paradigm was adopted in which participants had their arms bent behind their back or free during a spatial memory task. This task consisted in memorizing triads of objects and then verbally judging what was the object: (1) closest to/farthest from the participant (egocentric coordinate); (2) to the right/left of the participant (egocentric categorical); (3) closest to/farthest from a target object (allocentric coordinate); and (4) on the right/left of a target object (allocentric categorical). The triads appeared in participants' peripersonal (Experiment 1) or extrapersonal (Experiment 2) space. The results of Experiment 1 showed that motor interference selectively damaged egocentric-coordinate judgements but not the other spatial combinations. The results of Experiment 2 showed that the interference effect disappeared when the objects were in the extrapersonal space. A third follow-up study using a within-subject design confirmed the overall pattern of results. Our findings provide evidence that motor resources play an important role in the combination of coordinate spatial relations and egocentric representations in peripersonal space.     

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.     

How different spatial representations interact in virtual environments: the role of mental frame syncing

This experiment is aimed at understanding how egocentric experiences, allocentric viewpoint-dependent representations, and allocentric viewpoint-independent representations interact when encoding and retrieving a spatial environment. Although several cognitive theories have highlighted the interaction between reference frames, it is less clear about the role of a real-time presentation of allocentric viewpoint-dependent representation on the spatial organization of information. Sixty participants were asked to navigate in two virtual cities to memorize the position of one hidden object. Half of the participants had the possibility to visualize the virtual city with an interactive aerial view. Then, they were required to find the position of the object in three different experimental conditions (“retrieval with an interactive aerial view” vs. “retrieval on a map” vs. “retrieval without an interactive aerial view”). Results revealed that participants were significantly more precise in retrieving the position of the object when immersed in an egocentric experience with the interactive aerial view. The retrieval of spatial information is facilitated by the presence of the interactive aerial view of the city, since it provides a real-time allocentric viewpoint-dependent representation. More participants with high preference for using cardinal points tend to be more accurate when they were asked to retrieve the position of the object on the map. As suggested by the mental frame syncing hypothesis, the presence of an allocentric viewpoint-dependent representation during the retrieval seems to ease the imposition on a specific viewpoint on the stored abstract allocentric viewpoint-independent representation. Our findings represent another significant step toward the comprehension of the organization of spatial representations of our environment.     

The human parahippocampal cortex subserves egocentric spatial learning during navigation in a virtual maze

BackgroundPresent evidence suggests that the hippocampus (HC) and the parahippocampal cortex (PHC) are involved in allocentric (world-centered) spatial memory. However, the putative role of the PHC in egocentric (body-centered) spatial learning has received only limited systematic investigation.MethodsTo examine the role of the PHC in egocentric learning, 19 healthy volunteers learned to find their way in a virtual maze during functional magnetic resonance imaging (fMRI). The virtual maze presented a first-person view, lacked any topographical landmarks and could be learned only using egocentric navigation strategies.ResultsDuring learning, increased medial temporal lobe activity was observed in the PHC bilaterally. Activity was also observed in cortical areas known to project to the PHC and proposed to contribute to egocentric spatial navigation and memory.ConclusionsOur results point to a role of the PHC for the representation and storage of egocentric information. It seems possible that the PHC contributes to egocentric memory by its feedback projections to the posterior parietal cortex. Moreover, access to allocentric and egocentric streams of spatial information may enable the PHC to construct a global and comprehensive representation of spatial environments and to promote the construction of stable cognitive maps by translating between egocentric and allocentric frames of memory.     

Frames of reference in spatial span

In four experiments, a computerized Corsi-like paradigm was used to assess which of the many reference frames are used in visuospatial short-term memory. By varying the relative orientation (slanted +/-45° or in an upright position) of the head and the displays, we modulate the utility of the allocentric, egocentric (eye- and head-centred), and template-centred reference frames. The results of all experiments showed the crucial importance of the gravitational allocentric reference frames while using visuospatial short-term memory to retain a spatial sequence of elements. The results also provide some support for a mental rotation process involved in recognition following angular displacement of a multi-item display.     

人类路径整合的心理机制与神经基础

路径整合是指巡航者对与自身运动有关的信息进行整合来完成巡航任务的过程。这些与自身运动有关的信息可以是内源性的,如前庭感觉、本体感觉、动作指令的信息;也可以是外源性的,如视觉流。路径整合在许多物种中存在。人类路径整合的行为实验表明,以自我为参照系的空间表征和以环境为参照系的空间表征都有可能支持路径整合。神经科学的研究则表明,海马、内嗅皮层等内侧颞叶区域和以楔前叶等顶叶区域都与人类路径整合密切相关。     

The posterior parietal cortex and long-term memory representation of spatial information

The hypothesis to be explored in this chapter is based on the assumption that the posterior parietal cortex (PPC) is directly involved in representing a subset of the spatial features associated with spatial information processing and plays an important role in perceptual memory as well as long-term memory encoding, consolidation, and retrieval of spatial information. After presentation of the anatomical location of the PPC in rats, the nature of PPC representation based on single spatial features, binding of visual features associated with visual spatial attention, binding of object-place associations associated with acquisition and storage of associations where one of the elements is a spatial component, and binding of ideothetic and allothetic information in long-term memory is discussed. Additional evidence for a PPC role in mediation of spatial information in long-term storage is offered. Finally, the relationship between the PPC and the hippocampus from a systems and dynamic point view is presented.     

Spatial updating relies on an egocentric representation of space: Effects of the number of objects

Models of spatial updating attempt to explain how representations of spatial relationships between the actor and objects in the environment change as the actor moves. In allocentric models, object locations are encoded in an external reference frame, and only the actor’s position and orientation in that reference frame need to be updated. Thus, spatial updating should be independent of the number of objects in the environment (set size). In egocentric updating models, object locations are encoded relative to the actor, so the location of each object relative to the actor must be updated as the actor moves. Thus, spatial updating efficiency should depend on set size. We examined which model better accounts for human spatial updating by having people reconstruct the locations of varying numbers of virtual objects either from the original study position or from a changed viewing position. In consistency with the egocentric updating model, object localization following a viewpoint change was affected by the number of objects in the environment.     

Frames of reference in spatial span

In four experiments, a computerized Corsi-like paradigm was used to assess which of the many reference frames are used in visuospatial short-term memory. By varying the relative orientation (slanted +/–45° or in an upright position) of the head and the displays, we modulate the utility of the allocentric, egocentric (eye- and head-centred), and template-centred reference frames. The results of all experiments showed the crucial importance of the gravitational allocentric reference frames while using visuospatial short-term memory to retain a spatial sequence of elements. The results also provide some support for a mental rotation process involved in recognition following angular displacement of a multi-item display.     

Lateralization of egocentric and allocentric spatial processing after parietal brain lesions

The purpose of this paper was to verify whether left and right parietal brain lesions may selectively impair egocentric and allocentric processing of spatial information in near/far spaces. Two Right-Brain-Damaged (RBD), 2 Left-Brain-Damaged (LBD) patients (not affected by neglect or language disturbances) and eight normal controls were submitted to the Ego-Allo Task requiring distance judgments computed according to egocentric or allocentric frames of reference in near/far spaces. Subjects also completed a general neuropsychological assessment and the following visuospatial tasks: reproduction of the Rey-Osterreith figure, line length judgement, point position identification, mental rotation, mental construction, line length memory, line length inference, Corsi block-tapping task. LBD patients presented difficulties in both egocentric and allocentric processing, whereas RBD patients dropped in egocentric but not in allocentric judgements, and in near but not far space. Further, RBD patients dropped in perceptually comparing linear distances, whereas LBD patients failed in memory for distances. The overall pattern of results suggests that the right hemisphere is specialized in processing metric information according to egocentric frames of reference. The data are interpreted according to a theoretical model that highlights the close link between egocentric processing and perceptual control of action.     

Spatial working memory activity of the caudate nucleus is sensitive to frame of reference

We used event-related fMRI to test the hypothesis that the caudate nucleus is preferentially recruited by a spatial working memory task employing egocentrically defined stimuli, which are amenable to transformation into a motor code, as contrasted with allocentrically defined stimuli, which are not. Our results revealed greater delay-epoch activity in egocentric than in allocentric trials in the caudate nucleus and trends in the same direction in the putamen and the lateral premotor cortex (PMC). Response-related activity was greater for egocentric trials in the lateral PMC. We propose that the neostriatum, possibly interacting with the PMC, may contribute to the sensory-motor transformation necessary to establish a prospective motor code (e.g., the representation of a saccade or a grasp). In addition, the PMC may participate in decision-making processes, prompted by the onset of the probe stimulus, that employ this prospective motor information. This model accounts for the empirical evidence that motor distraction disrupts spatial working memory performance.     

Role of the parietal cortex in long-term representation of spatial information in the rat

The processing of spatial information in the brain requires a network of structures within which the hippocampus plays a prominent role by elaborating an allocentric representation of space. The parietal cortex has long been suggested to have a complementary function. An overview of lesion and unit recording data in the rat indicates that the parietal cortex is involved in different aspects of spatial information processing including allocentric and egocentric processing. More specifically, the data suggest that the parietal cortex plays a fundamental role in combining visual and motion information, a process that would be important for an egocentric-to-allocentric transformation process. Furthermore, the parietal cortex may also have a role in the long-term storage of representation although this possibility needs further evidence. The data overall show that the parietal cortex occupies a unique position in the brain at the interface of perception and representation.     

Individual Differences in the Encoding Processes of Egocentric and Allocentric Survey Knowledge

This study examined how different components of working memory are involved in the acquisition of egocentric and allocentric survey knowledge by people with a good and poor sense of direction (SOD). We employed a dual‐task method and asked participants to learn routes from videos with verbal, visual, and spatial interference tasks and without any interference. Results showed that people with a good SOD encoded and integrated knowledge about landmarks and routes into egocentric survey knowledge in verbal and spatial working memory, which is then transformed into allocentric survey knowledge with the support of all three components, distances being processed in verbal and spatial working memory and directions in visual and spatial working memory. In contrast, people with a poor SOD relied on verbal working memory and lacked spatial processing, thus failing to acquire accurate survey knowledge. Based on the results, a possible model for explaining individual differences in spatial knowledge acquisition is proposed.     

人类空间记忆和空间巡航

人类如何表征周围环境的空间结构信息,如何利用记忆中的空间表征来指导个体在环境中的空间活动,已成为认知心理学、神经科学、地理学以及人工智能研究的重要课题。文章综述了作者负责的实验室及其合作者近年来在视觉空间信息表征、基于运动的空间表征更新,以及认知系统中的不同空间信息处理模块等方面的研究工作,对以上问题及其内在的认知机制问题进行了初步的探讨