Allocentric Spatial Representations Research Articles

The Anterior Thalamus Preferentially Drives Allocentric But Not Egocentric Orientation Tuning in Postrhinal Cortex.

Navigating a complex world requires integration of multiple spatial reference frames, including information about one's orientation in both allocentric and egocentric coordinates. Combining these two information sources can provide additional information about one's spatial location. Previous studies have demonstrated that both egocentric and allocentric spatial signals are reflected by the firing of neurons in the rat postrhinal cortex (POR), an area that may serve as a hub for integrating allocentric head direction (HD) cell information with egocentric information from center-bearing and center-distance cells. However, we have also demonstrated that POR HD cells are uniquely influenced by the visual properties and locations of visual landmarks, bringing into question whether the POR HD signal is truly allocentric as opposed to simply being a response to visual stimuli. To investigate this issue, we recorded HD cells from the POR of female rats while bilaterally inactivating the anterior thalamus (ATN), a region critical for expression of the "classic" HD signal in cortical areas. We found that ATN inactivation led to a significant decrease in both firing rate and tuning strength for POR HD cells, as well as a disruption in the encoding of allocentric location by conjunctive HD/egocentric cells. In contrast, POR egocentric cells without HD tuning were largely unaffected in a consistent manner by ATN inactivation. These results indicate that the POR HD signal originates at least partially from projections from the ATN and supports the view that the POR acts as a hub for the integration of egocentric and allocentric spatial representations.

Features of spatial representations and orientation of yachtsmen during sailing races

The article presents a study of the predominant way of spatial representation by sailing athletes in the process of distance racing in natural conditions. It was revealed that allocentric spatial representations (ASP) prevail in sailing athletes in the whole sample (n=351), accounting for 79% of the total number. At the same time, egocentric spatial representations (ESP) in athletes make up 21%. The analysis of the distribution of spatial representations in athletes according to the level of sport qualification allowed us to identify a tendency of increasing the share of allocentric spatial representations with increasing sport grade, while the share of ESP decreases. The results of the study allow us to state that professional yachtsmen more often use ASP or switch between ASP and ESP, while novice yachtsmen, as a rule, use ESP.

Точность формирования пространственных репрезентаций динамических сцен в рабочей памяти

<p>The cognitive representation of the environment is formed using cognitive systems that process data on spatial representations of two types: egocentric, encoding the position of environmental objects relative to the observer, and allocentric, encoding the position of objects relative to each other, regardless of the position of the observer. Data on spatial representations were studied mainly in problems of memorization and reconstruction of static scenes. However, the task of processing information about dynamic scenes in everyday life has a higher ecological validity. We used HMD virtual reality technologies to study the accuracy of the formation of egocentric and allocentric spatial representations of static and dynamic scenes in working memory. The subjects were presented 8 three-dimensional virtual scenes of 4 objects each for 10 seconds in static and dynamic conditions for memorization and reconstruction. Identification accuracy (number of correctly reconstructed objects) and localization accuracy (accuracy of spatial scene reconstruction) were assessed. Localization accuracy was assessed in topological units, corresponding to the accuracy of the representation of the general configuration of objects in the scene (global topological information), and in metric units, corresponding to the accuracy of the representation of the spatial coordinates of each object (local metric information). The results showed that object identification accuracy was similar in static and dynamic conditions; the processes of encoding metric local information during the formation of both types of representations of dynamic scenes worsen compared to static ones; the accuracy of encoding topological global information remains stable compared to the static condition. We can conclude that the visual and spatial systems operate independently as part of a general cognitive system that processes data on spatial representations in time-limited working memory, as well as the redistribution of its resource in dynamic condition for supporting topological data of the holistic configuration of moving objects more, than metric data. The results highlight the importance of topological spatial characteristics of spatial representations for processes of early spatial perception, decision making, and action in the environment.</p>

The structure of cognitive strategies for wayfinding decisions

Literature proposes five distinct cognitive strategies for wayfinding decisions at intersections. Our study investigates whether those strategies rely on a generalized decision-making process, on two frame-specific processes—one in an egocentric and the other in an allocentric spatial reference frame, and/or on five strategy-specific processes. Participants took six trips along a prescribed route through five virtual mazes, each designed for decision-making by a particular strategy. We found that wayfinding accuracy on trips through a given maze correlated significantly with the accuracy on trips through another maze that was designed for a different reference frame (rbetween-frames = 0.20). Correlations were not significantly higher if the other maze was designed for the same reference frame (rwithin-frames = 0.19). However, correlations between trips through the same maze were significantly higher than those between trips through different mazes that were designed for the same reference frame (rwithin-maze = 0.52). We conclude that wayfinding decisions were based on a generalized cognitive process, as well as on strategy-specific processes, while the role of frame-specific processes—if any—was relatively smaller. Thus, the well-established dichotomy of egocentric versus allocentric spatial representations did not translate into a similar, observable dichotomy of decision-making.

Allocentric spatial representations dominate when switching between real and virtual worlds

Allocentric spatial representations dominate when switching between real and virtual worlds

Spatial orientation: A relationship with inferential memory

Two branches of the scientific literature have dominated our understanding of hippocampal function. One focuses on the support this structure offers to declarative memory, while the other views the hippocampus as a part of a system dedicated to spatial navigation. These two different visions can be reconciled in relational theory, which suggests that the hippocampus processes all kinds of associations and sequences of events. According to this, processing would be similar to a route calculation based on associations of spatial information acquired during navigation and the associative relationship established between memories without spatial content. In this paper, we present a behavioral study of healthy individuals to explore the performance of inferential memory tasks and spatial orientation tasks in a virtual environment. Inferential memory and spatial orientation task performances were positively correlated. However, after controlling for a non-inferential memory task, only the correlation between allocentric spatial orientation and inferential memory remained significant. These results provide support for the similarity between the two cognitive functions, lending credence to the relational theory of the hippocampus. Additionally, our behavioral findings are in line with the cognitive map theory, which suggests a potential association between the hippocampus and allocentric spatial representations.

Allocentric information represented by self-referenced spatial coding in the primate medial temporal lobe.

For living organisms, the ability to acquire information regarding the external space around them is critical for future actions. While the information must be stored in an allocentric frame to facilitate its use in various spatial contexts, each case of use requires the information to be represented in a particular self-referenced frame. Previous studies have explored neural substrates responsible for the linkage between self-referenced and allocentric spatial representations based on findings in rodents. However, the behaviors of rodents are different from those of primates in several aspects; for example, rodents mainly explore their environments through locomotion, while primates use eye movements. In this review, we discuss the brain mechanisms responsible for the linkage in nonhuman primates. Based on recent physiological studies, we propose that two types of neural substrates link the first-person perspective with allocentric coding. The first is the view-center background signal, which represents an image of the background surrounding the current position of fixation on the retina. This perceptual signal is transmitted from the ventral visual pathway to the hippocampus (HPC) via the perirhinal cortex and parahippocampal cortex. Because images that share the same objective-position in the environment tend to appear similar when seen from different self-positions, the view-center background signals are easily associated with one another in the formation of allocentric position coding and storage. The second type of neural substrate is the HPC neurons' dynamic activity that translates the stored location memory to the first-person perspective depending on the current spatial context.

The Role of Temporal Order in Egocentric and Allocentric Spatial Representations.

Several studies have shown that spatial information is encoded using two types of reference systems: egocentric (body-based) and/or allocentric (environment-based). However, most studies have been conducted in static situations, neglecting the fact that when we explore the environment, the objects closest to us are also those we encounter first, while those we encounter later are usually those closest to other environmental objects/elements. In this study, participants were shown with two stimuli on a computer screen, each depicting a different geometric object, placed at different distances from them and an external reference (i.e., a bar). The crucial manipulation was that the stimuli were shown sequentially. After participants had memorized the position of both stimuli, they had to indicate which object appeared closest to them (egocentric judgment) or which object appeared closest to the bar (allocentric judgment). The results showed that egocentric judgements were facilitated when the object closest to them was presented first, whereas allocentric judgements were facilitated when the object closest to the bar was presented second. These results show that temporal order has a different effect on egocentric and allocentric frames of reference, presumably rooted in the embodied way in which individuals dynamically explore the environment.

Multifactor mid‐life risk for Alzheimer’s disease associated with alterations in navigation but not episodic memory: the PREVENT‐Dementia study

AbstractBackgroundThe entorhinal cortex (EC) is the first cortical brain region to exhibit neurodegeneration in Alzheimer’s disease (AD). Given that the EC contains unique grid cells underpinning path integration, tests probing this aspect of navigation may have added value in detecting AD in its earliest preclinical stages. Building on our past work showing that a VR path integration task was highly sensitive and specific for prodromal AD (Howett et al., 2019 Brain), we tested the hypothesis that path integration may be affected in asymptomatic middle‐aged individuals at increased risk of AD.Method100 cognitively healthy adults (aged 43–66) from the PREVENT Dementia cohort performed an immersive VR path integration task in a simulated environment with distal boundary cues to generate allocentric spatial representations. We manipulated EC‐dependence by pseudo‐randomly removing supportive spatial cues from the virtual environment (Figure 1). Participants additionally performed a battery of cognitive tasks including the ACE‐R and COGNITO episodic memory. Linear mixed effects models and Tukey‐corrected post‐hoc contrasts were used to explore the contributions to task performance of parental family history, APOE‐e4 status, global amyloid PET uptake value (N = 46) and CAIDE lifestyle dementia risk score, adjusted for age, sex and education.ResultIndividuals with a positive family history, APOE‐e4 allele or higher CAIDE dementia risk score showed a selective impairment in path integration only when supportive boundary cues were removed. Significant sex interactions indicated that the family history effect (t = 2.31, pTukey = 0.022, Figure 2) and APOE‐e4 effect (t = 3.18, pTukey = 0.023) was specific to males. The effect of CAIDE risk score was specific to individuals with a family history (t = 2.45, pTukey = 0.038) (Figure 3). Conversely, these AD risk factors showed no effect on performance for the other cognitive tasks. Global amyloid PET uptake values showed no association to any task performance.ConclusionThese results suggest that navigation tests based on EC grid cell function may identify the earliest cognitive changes in individuals at greater risk of AD. The additional moderation by sex indicates a future need to consider male/female differences when using family history or APOE status to inform detection of initial stages of AD.

Navigation task and action space drive the emergence of egocentric and allocentric spatial representations.

In general, strategies for spatial navigation could employ one of two spatial reference frames: egocentric or allocentric. Notwithstanding intuitive explanations, it remains unclear however under what circumstances one strategy is chosen over another, and how neural representations should be related to the chosen strategy. Here, we first use a deep reinforcement learning model to investigate whether a particular type of navigation strategy arises spontaneously during spatial learning without imposing a bias onto the model. We then examine the spatial representations that emerge in the network to support navigation. To this end, we study two tasks that are ethologically valid for mammals-guidance, where the agent has to navigate to a goal location fixed in allocentric space, and aiming, where the agent navigates to a visible cue. We find that when both navigation strategies are available to the agent, the solutions it develops for guidance and aiming are heavily biased towards the allocentric or the egocentric strategy, respectively, as one might expect. Nevertheless, the agent can learn both tasks using either type of strategy. Furthermore, we find that place-cell-like allocentric representations emerge preferentially in guidance when using an allocentric strategy, whereas egocentric vector representations emerge when using an egocentric strategy in aiming. We thus find that alongside the type of navigational strategy, the nature of the task plays a pivotal role in the type of spatial representations that emerge.

Associations between developmental exposure to environmental contaminants and spatial navigation in late adolescence.

Inuit communities in Northern Quebec (Canada) are exposed to environmental contaminants, particularly to mercury, lead and polychlorinated biphenyls (PCBs). Previous studies reported adverse associations between these neurotoxicants and memory performance. Here we aimed to determine the associations of pre- and postnatal exposures to mercury, lead and PCB-153 on spatial navigation memory in 212 Inuit adolescents (meanage=18.5 years) using a computer task which requires learning the location of a hidden platform based on allocentric spatial representation. Contaminant concentrations were measured in cord blood at birth and blood samples at 11 years of age and at time of testing. Multivariate regression models showed that adolescent mercury and prenatal PCB-153 exposures were associated with poorer spatial learning, whereas current exposure to PCB-153 was associated with altered spatial memory retrieval at the probe test trial. These findings suggest that contaminants might be linked to different aspects of spatial navigation processing at different stages.

A Behavioral Task Modeling 'Everyday Memory' in an Event Arena to Foster Allocentric Representations for Rodents.

The event arena provides an optimal platform to investigate learning and memory. The appetitive everyday memory task described in this paper provides a robust protocol for the investigation of episodic and spatial memory in rodents, which specifically fosters allocentric memory representation. Rats are trained to find and dig for food during the encoding phase and, after a time delay, rats are given a choice to find the reward food pellet in the correct location. There are two key elements that promote the use of an allocentric strategy in this protocol: 1) rats start from different start locations within and between sessions, 2) a stable home-base is deployed where rats have to carry their food to eat. By means of these modifications, we effectively encourage the rodents to use allocentric spatial representations to perform the task. In addition, the task provides a good paradigm for within-subject experimental design and allows experimenters to manipulate different conditions to reduce variability. Used in conjunction with behavioral and physiological techniques, the resulting rodent model provides an effective test-bed for future research into memory formation and retention.

The Accuracy of Allocentric and Egocentric Spatial Representations in Working Memory

The Accuracy of Allocentric and Egocentric Spatial Representations in Working Memory

A Critical Review of Spatial Abilities in Down and Williams Syndromes: Not All Space Is Created Equal.

Down syndrome (DS, Trisomy 21) and Williams syndrome (WS) are two neurodevelopmental disorders of genetic origin that are accompanied by mild to moderate intellectual disability but exhibit distinct cognitive profiles. In this review we discuss our recent work characterizing the real-world spatial learning and memory abilities of adult individuals with DS and WS. We used several different paradigms in which participants locomote freely and have access to coherent input from all sensory modalities to investigate their fundamental egocentric (body-centered or viewpoint-dependent) and allocentric (world-centered or viewpoint-independent) spatial abilities. We found unequivocal evidence that most individuals with DS exhibit low-resolution egocentric and allocentric spatial learning and memory abilities similar to typically developing (TD) children in the same mental age range. In contrast, most individuals with DS exhibit impaired high-resolution allocentric spatial learning and facilitated response learning as compared to TD children. In comparison, whereas most individuals with WS also exhibit facilitated response learning, their low-resolution allocentric spatial learning and memory abilities are severely impaired as compared to both TD children and individuals with DS. Together with work from other laboratories using real-world or virtual reality paradigms, these findings indicate that in order to navigate in their environment most individuals with DS may use either egocentric route learning that does not integrate individual landmarks, or a low-resolution allocentric spatial representation that encodes the relationships between different locations (i.e., cognitive mapping). In contrast, since most individuals with WS are unable to build or use a low-resolution allocentric or configural representation of the environment they may use visually and verbally encoded landmarks as beacons to learn routes. Finally, we discuss the main neural structures implicated in these different spatial processes and explain how the relative preservation or impairment of specific brain functions may engender the unique cognitive profiles observed in individuals with these neurodevelopmental disorders.

Subthreshold membrane potential dynamics of posterior parietal cortical neurons coupled with hippocampal ripples.

During behavioral states of immobility, sleep, and anesthesia, the hippocampus generates high-frequency oscillations called ripples. Ripples occur simultaneously with synchronous neuronal activity in the neocortex, known as slow waves, and contribute to memory consolidation. During these ripples, various neocortical regions exhibit modulations in spike rates and local field activity irrespective of whether they receive direct synaptic inputs from the hippocampus. However, little is known about the subthreshold dynamics of the membrane potentials of neocortical neurons during ripples. We patch-clamped layer 2/3 pyramidal cells in the posterior parietal cortex (PPC), a neocortical region that is involved in allocentric spatial representation of behavioral exploration and sequential series of relevant action potentials during ripples. We simultaneously monitored the membrane potentials of post hoc-identified PPC neurons and the local field potentials of the hippocampus in anesthetized mice. More than 50% of the recorded PPC neurons exhibited significant depolarizations and/or hyperpolarizations during ripples. Histological inspections of the recorded neurons revealed that the ripple-modulated PPC neurons were distributed in the PPC in a spatially non-biased fashion. These results suggest that hippocampal ripples are widely but selectively associated with the subthreshold dynamics of the membrane potentials of PPC neurons even though there is no monosynaptic connectivity between the hippocampus and the PPC.

Representation of Contralateral Visual Space in the Human Hippocampus.

The initial encoding of visual information primarily from the contralateral visual field is a fundamental organizing principle of the primate visual system. Recently, the presence of such retinotopic sensitivity has been shown to extend well beyond early visual cortex to regions not historically considered retinotopically sensitive. In particular, human scene-selective regions in parahippocampal and medial parietal cortex exhibit prominent biases for the contralateral visual field. Here, we used fMRI to test the hypothesis that the human hippocampus, which is thought to be anatomically connected with these scene-selective regions, would also exhibit a biased representation of contralateral visual space. First, population receptive field (pRF) mapping with scene stimuli revealed strong biases for the contralateral visual field in bilateral hippocampus. Second, the distribution of retinotopic sensitivity suggested a more prominent representation in anterior medial portions of the hippocampus. Finally, the contralateral bias was confirmed in independent data taken from the Human Connectome Project (HCP) initiative. The presence of contralateral biases in the hippocampus, a structure considered by many as the apex of the visual hierarchy, highlights the truly pervasive influence of retinotopy. Moreover, this finding has important implications for understanding how visual information relates to the allocentric global spatial representations known to be encoded therein.SIGNIFICANCE STATEMENT Retinotopic encoding of visual information is an organizing principle of visual cortex. Recent work demonstrates this sensitivity in structures far beyond early visual cortex, including those anatomically connected to the hippocampus. Here, using population receptive field (pRF) modeling in two independent sets of data we demonstrate a consistent bias for the contralateral visual field in bilateral hippocampus. Such a bias highlights the truly pervasive influence of retinotopy, with important implications for understanding how the presence of retinotopy relates to more allocentric spatial representations.

Learning allocentric representations of space for navigation

The hippocampus of the mammalian brain supports spatial navigation by building cognitive maps of the environments in which the animal explores. Currently, there is little neurocomputational work investigating the encoding and decoding mechanisms of hippocampal neural representations in large-scale environments. We propose a biologically-inspired hierarchical neural network architecture to learn the transformation of egocentric sensorimotor inputs into allocentric spatial representation for navigation. The hierarchical network is composed of two parallel subnetworks mimicking the lateral entorhinal cortex (LEC) and medial entorhinal cortex (MEC), and one convergent subnetwork mimicking the hippocampus. LEC relays time-related visual information and MEC supplies space-related information in the form of multi-resolution grid codes as resulted from integrating movement information. The convergent subnetwork integrates all information from the parallel subnetworks and predicts the position of the agent in the environment. Synaptic weights of the vision-to-place and grid-to-place connections are learned based on the stochastic gradient descent algorithm. Simulations in a large virtual maze demonstrate that hippocampal place units in the model form multiple and irregularly-spaced place fields, similar to those observed in neurobiological experiments. The model is able to accurately decode the positions of the agent from the learned spatial representations. Moreover, the model is capable of adaptation to degraded visual inputs, and therefore is robust against perturbations. When the motion inputs are deprived, the model meets with localization difficulty, suffering from less accuracy in position predictions.

Allocentric coordinate spatial representations are impaired in aMCI and Alzheimer’s disease patients

Research has reported deficits in egocentric (subject-to-object) and mainly allocentric (object-to-object) spatial representations in the early stages of the Alzheimer’s disease (eAD). To identify early cognitive signs of neurodegenerative conversion, several studies have shown alterations in both reference frames, especially the allocentric ones in amnestic-Mild Cognitive Impairment (aMCI) and eAD patients. However, egocentric and allocentric spatial frames of reference are intrinsically connected with coordinate (metric/variant) and categorical (non-metric/invariant) spatial relations. This raises the question of whether allocentric deficit found to detect the conversion from aMCI to dementia is differently affected when combined with categorical or coordinate spatial relations. Here, we compared eAD and aMCI patients to Normal Controls (NC) on the Ego-Allo/Cat-Coor spatial memory task. Participants memorized triads of objects and then were asked to provide right/left (i.e. categorical) and distance based (i.e. coordinate) judgments according to an egocentric or allocentric reference frame. Results showed a selective deficit of coordinate, but not categorical, allocentric judgments in both aMCI and eAD patients as compared to NC group. These results suggest that a sign of the departure from normal/healthy aging towards the AD may be traced in elderly people’s inability to represent metric distances among elements in the space.

Children five-to-nine years old can use path integration to build a cognitive map without vision

Although spatial navigation competence improves greatly from birth to adulthood, different spatial memory capacities emerge at different ages. Here, we characterized the capacity of 5–9-year-old children to use path integration to build egocentric and allocentric spatial representations to navigate in their environment, and compared their performance with that of young adults. First, blindfolded participants were tested on their ability to return to a starting point after being led on straight and two-legged paths. This egocentric homing task comprising angular and linear displacements allowed us to evaluate path integration capacities in absence of external landmarks. Second, we evaluated whether participants could use path integration, in absence of visual information, to create an allocentric spatial representation to navigate along novel paths between objects, and thus demonstrate the ability to build a cognitive map of their environment. Ninety percent of the 5–9-year-old children could use path integration to create an egocentric representation of their journey to return to a starting point, but they were overall less precise than adults. Sixty-four percent of 5–9-year-old children were capable of using path integration to build a cognitive map enabling them to take shortcuts, and task performance was not dependent on age. Imprecisions in novel paths made by the children who built a cognitive map could be explained by poorer integration of the experienced turns during the learning phase, as well as greater individual variability. In sum, these findings demonstrate that 5–9-year-old children can use path integration to build a cognitive map in absence of visual information.

Postnatal development of the entorhinal cortex: A stereological study in macaque monkeys.

The entorhinal cortex is the main gateway for interactions between the neocortex and the hippocampus. Distinct regions, layers, and cells of the hippocampal formation exhibit different profiles of structural and molecular maturation during postnatal development. Here, we provide estimates of neuron number, neuronal soma size, and volume of the different layers and subdivisions of the monkey entorhinal cortex (Eo, Er, Elr, Ei, Elc, Ec, Ecl) during postnatal development. We found different developmental changes in neuronal soma size and volume of distinct layers in different subdivisions, but no changes in neuron number. Layers I and II developed early in most subdivisions. Layer III exhibited early maturation in Ec and Ecl, a two-step/early maturation in Ei and a late maturation in Er. Layers V and VI exhibited an early maturation in Ec and Ecl, a two-step and early maturation in Ei, and a late maturation in Er. Neuronal soma size increased transiently at 6 months of age and decreased thereafter to reach adult size, except in Layer II of Ei, and Layers II and III of Ec and Ecl. These findings support the theory that different hippocampal circuits exhibit distinct developmental profiles, which may subserve the emergence of different hippocampus-dependent memory processes. We discuss how the early maturation of the caudal entorhinal cortex may contribute to path integration and basic allocentric spatial processing, whereas the late maturation of the rostral entorhinal cortex may contribute to the increased precision of allocentric spatial representations and the temporal integration of individual items into episodic memories.