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Abstract: Unilateral infusion of 6-hydroxydopamine into the nigro-striatal pathway in the rat is the most common dopamine lesion model of Parkinson's disease. In the present study, we explore the impact of near complete unilateral loss of dopamine along the nigro-striatal pathway and subsequent cell replacement therapy in a choice reaction time task in rats, with assessment of spatial responding towards either side of the body (ipsilateral or contralateral to the lesion) on alternate days. Results indicated a stable contralateral deficit in response accuracy, reaction times and motor function for 50 consecutive days of testing, with no signs of recovery or compensation. All lesioned rats developed a near-hole bias and displayed prolonged movement and reaction times when responses had to be directed towards a distal response location on the side of the body contralateral to the lesion, as well as a smaller ipsilateral impairment in response accuracy and movement times. Grafts of dopamine-rich tissue into the denervated striatum improved some, but not all, of the deficits induced by the lesion. Specifically, grafted rats performed at a similar level to control animals when assessed on the ipsilateral side, they demonstrated a partial restitution of their ability to respond to far contralateral stimuli, and they exhibited a marked reduction in the time to complete all lateralised responses on both sides. The present characterisation of the task and the effects of cell replacement via primary fetal mesencephalic tissue demonstrate restorative properties in alleviating the marked spatial response bias induced by unilateral loss of dopamine. [Copyright &y& Elsevier]

Performance on tactile temporal order judgments (TOJs) is impaired when the hands are crossed over the midline. The cause of this effect appears to be tied to the use of an external reference frame, most likely based on visual information. We measured the effect of degrading the external reference frame on the crossed-hand deficit through restriction of visual information across three experiments. Experiments 1 and 2 examined three visual conditions (eyes open-lights on, eyes open-lights off, and eyes closed-lights off) while manipulating response demands; no effect of visual condition was seen. In Experiment 3, response demands were altered to be maximally connected to the internal reference frame and only two visual conditions were tested: eyes open-lights on, eyes closed-lights off. Blindfolded participants had a reduced crossed-hands deficit. Results are discussed in terms of the time needed to recode stimuli from an internal to an external reference frame and the role of conflict between these two reference frames in causing this effect. [ABSTRACT FROM AUTHOR]

Posterior parahippocampal gyrus (PPHG) is strongly involved during scene recognition and spatial cognition. How PPHG electrophysiological activity could underlie these functions, and whether they share similar timing mechanisms is unknown. We addressed this question in two intracerebral experiments which revealed that PPHG neural activity dissociated an early stimulus-driven effect (>200 and <500 ms) and a late task-related effect (>600 and <800 ms). Strongest PPHG gamma band (50-150 Hz) activities were found early when subjects passively viewed scenes (scene selectivity effect) and lately when they had to estimate the position of an object relative to the environment (allocentric effect). Based on single trial analyses, we were able to predict when patients viewed scenes (compared to other visual categories) and when they performed allocentric judgments (compared to other spatial judgments). The anatomical location corresponding to the strongest effects was in the depth of the collateral sulcus. Our findings directly affect current theories of visual scene processing and spatial orientation by providing new timing constraints and by demonstrating the existence of separable information processing stages in the functionally defined parahippocampal place area. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: Background: Previous research on hemispatial neglect has provided evidence for dissociable mechanisms for egocentric and allocentric processing. Although a few studies have examined whether tDCS to posterior parietal cortex can be beneficial for attentional processing in neurologically intact individuals, none have examined the potential effect of tDCS on allocentric and/or egocentric processing. Objective/hypothesis: Our objective was to examine whether transcranial direct current stimulation (tDCS), a noninvasive brain stimulation technique that can increase (anodal) or decrease (cathodal) cortical activity, can affect visuospatial processing in an allocentric and/or egocentric frame of reference. Methods: We tested healthy individuals on a target detection task in which the target – a circle with a gap – was either to the right or left of the viewer (egocentric), or contained a gap on the right or left side of the circle (allocentric). Individuals performed the task before, during, and after tDCS to the posterior parietal cortex in one of three stimulation conditions – right anodal/left cathodal, right cathodal/left anodal, and sham. Results: We found an allocentric hemispatial effect both during and after tDCS, such that right anodal/left cathodal tDCS resulted in faster reaction times for detecting stimuli with left-sided gaps compared to right-sided gaps. Conclusions: Our study suggests that right anodal/left cathodal tDCS has a facilitatory effect on allocentric visuospatial processing, and might be useful as a therapeutic technique for individuals suffering from allocentric neglect. [Copyright &y& Elsevier]

Aims To apply social network analysis ( SNA) to investigate whether frequency and severity of gambling problems were associated with different network characteristics among friends, family and co-workers is an innovative way to look at relationships among individuals; the current study was the first, to our knowledge, to apply SNA to gambling behaviors. Design Egocentric social network analysis was used to characterize formally the relationships between social network characteristics and gambling pathology. Setting Laboratory-based questionnaire and interview administration. Participants Forty frequent gamblers (22 non-pathological gamblers, 18 pathological gamblers) were recruited from the community. Measurements and Findings The SNA revealed significant social network compositional differences between the two groups: pathological gamblers ( PGs) had more gamblers, smokers and drinkers in their social networks than did non-pathological gamblers ( NPGs). PGs had more individuals in their network with whom they personally gambled, smoked and drank than those with who were NPG. Network ties were closer to individuals in their networks who gambled, smoked and drank more frequently. Associations between gambling severity and structural network characteristics were not significant. Conclusions Pathological gambling is associated with compositional but not structural differences in social networks. Pathological gamblers differ from non-pathological gamblers in the number of gamblers, smokers and drinkers in their social networks. Homophily within the networks also indicates that gamblers tend to be closer with other gamblers. This homophily may serve to reinforce addictive behaviors, and may suggest avenues for future study or intervention. [ABSTRACT FROM AUTHOR]

Episodic memory loss is a defining feature of early-stage Alzheimer's disease (AD). A test of episodic-like memory for the rat, the What-Where-Which occasion task (WWWhich), requires the association of object, location, and contextual information to form an integrated memory for an event. The WWWhich task cannot be solved by use of non-episodic information such as object familiarity and is dependent on hippocampal integrity. Thus, it provides an ideal tool with which to test capacity for episodic-like memory in the 3xTg murine model for AD. As this model captures much of the human AD phenotype, we hypothesized that these mice would show a deficit in the WWWhich episodic-like memory task. To test the specificity of any episodic-like deficit, we also examined whether mice could perform components of the WWWhich task that do not require episodic-like memory. These included object (Novel Object Recognition), location (Object Location Task, What-Where task), and contextual (What-Which) memory, as well as another three-component task that can be solved without reliance on episodic recall (What-Where-When; WWWhen). The results demonstrate for the first time that control 129sv/c57bl6 mice could form WWWhich episodic-like memories, whereas, 3xTgAD mice at 6 months of age were impaired. Importantly, while 3xTgAD mice showed some deficit on spatial component tasks, they were unimpaired in the more complex WWWhen combination task (which includes a spatial component and is open to non-episodic solutions). These results strongly suggest that AD pathology centered on the hippocampal formation mediates a specific deficit for WWWhich episodic-like memory in the 3xTgAD model. [ABSTRACT FROM AUTHOR]

Abstract: Unilateral dopamine depletion and excitotoxic lesions of the striatum have been shown to induce a contralateral neglect when rats have to respond in a choice reaction time setting. Whereas, in a lateralised setting when response options are to either side of the animal''s head all contralateral responding is impaired, testing animals only on one side of the head per day but with a near and far response option, rats are able to correctly respond to contralateral stimuli, but rather bias their responses towards the near hole. Here, we further investigated the nature of the contralateral neglect in egocentric space coding in more detail. Firstly, we tested the effects of near-complete unilateral dopamine depletion on this type of task. Secondly, previous observations suggested that lesioned rats shifted their response strategy which resulted in a response bias towards the most proximal location in contralateral space. In order to “encourage” dopamine depleted rats to respond to the neglected response location we implemented an error correction procedure to the task. Near-complete unilateral dopamine depletion, via 6-hydroxydopamine infusions into the medial forebrain bundle of female Lister Hood rats, resulted in a reduction of usable trials, a near hole bias when animals were tested on the side contralateral to the lesion, as well as increased reaction and movement time latencies. The introduction of an error-correction procedure had no effect on the animals’ response bias towards the near contralateral location. Probe trials showed that the bias is most likely the result of responses being misdirected when in a choice situation. The findings further highlight the role of dopamine and an intact striatum to code responses into egocentrically defined space. [Copyright &y& Elsevier]

Abstract: Previous studies showed egocentric but not allocentric mental rotation tasks to be impaired in microgravity when feedback cues about vertical surroundings were restricted. Those studies are difficult to reconcile, however, since they were limited not only to small subject groups, but also differed dramatically in design. According to this lack, the present study was conducted in order to compare three typical egocentric and allocentric mental rotation stimuli in microgravity within a single experiment and using the same subjects and setup conditions. In order to simulate astronauts’ working conditions in space, visual and tactile vertical references were provided. Six subjects mentally rotated letters, body parts, and complex scenes in parabolic flight during near-weightlessness and level flight conditions. Subjects viewed letters and judged whether they were mirror-reversed or not (task LETTER), viewed pictures of a hand and assessed whether it was a right or a left hand (task HAND), and viewed drawings of a person at a table that contained both a weapon and a rose and had to decide whether the weapon was on the right or left side of the table (task SCENE). Material could be in canonical orientation or rotated from 0° up to 180° in ±60° steps. We calculated reaction times and error scores for each task, orientation in each condition, and performed additionally intra-subject correlations between reaction times of both conditions for each task. We found typical reaction times and error scores for each stimulus category with increasing rotation level. More importantly, response time and error score were not impaired in microgravity, independent of stimulus type and orientation. This finding is further confirmed by correlation analysis. We conclude that the mental rotation of letters, hand shapes, and complex scenes is not affected by short periods in microgravity when visual and tactile vertical references are provided. This finding is relevant for astronauts who are normally aware of their surroundings, and it is in accordance with previous findings, where only egocentric stimuli were impaired in microgravity when sensory cues about the vertical reference were restricted. [Copyright &y& Elsevier]

Allocentric (landmark-centered) and egocentric (eye-centered) visual codes are fundamental for spatial cognition, navigation, and goal-directed movement. Neuroimaging and neurophysiology suggest these codes are initially segregated, but then reintegrated in frontal cortex for movement control. We created and validated a theoretical framework for this process using physiologically constrained inputs and outputs. To implement a general framework, we integrated a convolutional neural network (CNN) of the visual system with a multilayer perceptron (MLP) model of the sensorimotor transformation. The network was trained on a task where a landmark shifted relative to the saccade target. These visual parameters were input to the CNN, the CNN output and initial gaze position to the MLP, and a decoder transformed MLP output into saccade vectors. Decoded saccade output replicated idealized training sets with various allocentric weightings and actual monkey data where the landmark shift had a partial influence ( R  = 0.8). Furthermore, MLP output units accurately simulated prefrontal response field shifts recorded from monkeys during the same paradigm. In summary, our model replicated both the general properties of the visuomotor transformations for gaze and specific experimental results obtained during allocentric-egocentric integration, suggesting it can provide a general framework for understanding these and other complex visuomotor behaviors.2  = 0.8). Furthermore, MLP output units accurately simulated prefrontal response field shifts recorded from monkeys during the same paradigm. In summary, our model replicated both the general properties of the visuomotor transformations for gaze and specific experimental results obtained during allocentric-egocentric integration, suggesting it can provide a general framework for understanding these and other complex visuomotor behaviors., (© The Author(s) 2022. Published by Oxford University Press.)

In this paper, we propose a general framework for local path-planning and steering that can be easily extended to perform high-level behaviors. Our framework is based on the concept of affordances: the possible ways an agent can interact with its environment. Each agent perceives the environment through a set of vector and scalar fields that are represented in the agent's local space. This egocentric property allows us to efficiently compute a local space-time plan and has better parallel scalability than a global fields approach. We then use these perception fields to compute a fitness measure for every possible action, defined as an affordance field. The action that has the optimal value in the affordance field is the agent's steering decision. We propose an extension to a linear space-time prediction model for dynamic collision avoidance and present our parallelization results on multicore systems. We analyze and evaluate our framework using a comprehensive suite of test cases provided in SteerBench and demonstrate autonomous virtual pedestrians that perform steering and path planning in unknown environments along with the emergence of high-level responses to never seen before situations. [ABSTRACT FROM AUTHOR]

Dysfunction of the neostriatum, a primary feature of several neurodegenerative disorders, including Parkinson's disease and Huntington's disease, has been found to result in impaired localisation of, and reaction to, contralateral stimuli. On the basis of previous findings, it is hypothesised that, with increasing eccentricity of the response option, striatal cell loss may impair response localisation at the furthest levels of eccentricity, whereas dopamine (DA) depletion may not impact adversely upon responses executed in this extrapersonal space. In order to elucidate more fully the function of the striatum, the present study examined the differential impact of unilateral DA depletion or excitoxic lesion on response execution in ipsilateral and contralateral space at up to four levels of eccentricity. The results confirmed that, after both types of striatal dysfunction, the sensory ability to detect stimuli remains intact, whereas the ability to direct responses in absolute contralateral space is impaired. Distinct differences in the profiles of impairment were, however, evident, with a marked increase in response omissions observed after DA depletion, which may reflect decreased motivational processing, and recovery of function observed in rats with excitotoxic lesions, which suggests the ability to re-learn. Furthermore, the data demonstrate that, after cell loss, responding in near contralateral space is controlled by competing striata, whereas responding in extrapersonal space relies on the contralateral hemisphere. These results have implications for understanding the role of the striatum in egocentrically defined response localisation, as well as for unravelling the behavioural impact of striatal cell loss or aberrant DA transmission observed in neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Abstract: This study compares mental rotation with three stimuli: letters, body parts and complex scenes. Twenty-four subjects saw letters and judged whether they were mirror-reversed or not (task LETTER), saw pictures of a hand and indicated whether it was a right or a left one (task HAND), and saw drawings of a person at a table on which a weapon and a rose laid and decided whether the weapon was to the person’s right or left (task SCENE). Stimuli were presented in canonical orientation or rotated by up to 180°. Our analyses focused on intra-subject correlations between reaction times of the different tasks. We found that reaction times for stimuli in canonical orientation co-varied in HAND and LETTER, the increase of reaction times with increasing object rotation co-varied in HAND and SCENE, and reaction times for 180° rotations co-varied between all tasks. We suggest that basic processes like visual perception and decision-making are distinct for scenes versus letters and body parts, that the mechanism for mental rotation of letters is distinct from that for mental self- and body part rotation, and suggest an extra mechanism for 180° rotations that shared among all tasks. These findings confirm and expand hypotheses about mental rotation that were based on comparisons of between-subject means. [Copyright &y& Elsevier]

Similarity between partners entails positive consequences for cooperative interactions. But do people rely on this assumption to construe egocentric judgments about others? Five experiments examined the possibility that people project onto their partners because they believe that similarity to the self leads to success in cooperation. Studies 1a and 1b show that people hold an egocentric similarity belief in cooperation. Studies 2a and 2b test the existence of this belief in more indirect ways. The next three studies manipulate the applicability of the similarity belief and investigate its impact on projection. Study 3 finds that cooperation no longer leads to projection when participants expect a low probability of success. Study 4 replicates this effect in a real cooperative setting. Finally, Study 5 shows that projection occurs only when participants expect their characteristics to be responsible for the success of cooperation. The negative consequences of overestimating similarities in cooperation are discussed. [ABSTRACT FROM AUTHOR]

Prior experiences of a stimulus facilitate reprocessing of that stimulus on a subsequent occasion. This relative ease and speed with which information is processed is defined as fluency and can constitute a basis for memory judgment. Fluency can also be manipulated on line by perceptual bias (e.g., levels of noise), leading to an increase in recognition for items processed more fluently (e.g., items with less noise). Previous experiments using Remember-Know paradigm have shown an impact of perceptual fluency only on familiarity and not on recollection. Recent episodic memory models have postulated a strong link between episodic memory and spatial processes, especially with egocentric updating (Gomez et al. in Acta Psychol 132(3):221-227, ). The present experiment was conducted to determine whether self-motion fluency affects recognition performance and particularly has an impact on 'Remember' responses. Thirty participants learned a 4-min path movie and then had to recognize among short paths if they were part of the learned path, followed by a Remember-Know procedure for recognized items. Self-motion fluency was manipulated with the presence of nimble acceleration applied on a small part of the recognition paths. Results show that the presence of a self-motion fluency increases significantly the proportion of remember responses solely on learned paths. This study spotlights for the first time a specific fluency effect on recollection and indicates an implication of egocentric-updating processing in episodic memory retrieval. [ABSTRACT FROM AUTHOR]

Unilateral visual neglect is commonly defined as impaired ability to attend to stimuli presented on the side of visual space contralateral to the brain lesion. However, behavioral analyses indicate that different neglect symptoms can dissociate.The neuroanatomy of the syndrome has been hotly debated. Some groups have argued that the syndrome is linked to posterior parietal cortex lesions, while others report damage within regions including the superior temporal gyrus, insula, and basal ganglia. Several recent neuroimaging studies provide evidence that heterogeneity in the behavioral symptoms of neglect can be matched by variations in the brain lesions, and that some of the discrepancies across earlier findings might have resulted from the use of different neuropsychological tests and/or varied measures within the same task for diagnosing neglect. In this paper, we review the evidence for dissociations between both the symptoms and the neural substrates of unilateral visual neglect, drawing on ALE (anatomic likelihood estimation) meta-analyses of lesion-symptom mapping studies. Specifically, we examine dissociations between neglect symptoms associated with impaired control of attention across space (in an egocentric frame of reference) and within objects (in an allocentric frame of reference). Results of ALE meta-analyses indicated that, while egocentric symptoms are associated with damage within perisylvian network (pre- and postcentral, supramarginal, and superior temporal gyri) and damage within sub-cortical structures, more posterior lesions including the angular, middle temporal, and middle occipital gyri are associated with allocentric symptoms. Furthermore, there was high concurrence in deficits associated with white matter lesions within long association (superior longitudinal, inferior fronto-occipital, and inferior longitudinal fasciculi) and projection (corona radiata and thalamic radiation) pathways, supporting a disconnection account of the syndrome. Using this evidence we argue that different forms of neglect link to both distinct and common patterns of gray and white matter lesions.The findings are discussed in terms of functional accounts of neglect and theoretical models based on computational studies of both normal and impaired attention functions. [ABSTRACT FROM AUTHOR]

Considerable evidence indicates that males navigate large-scale space better than females, and some have previously attributed this difference to a greater ability of males to select or use an allocentric (cognitive mapping) navigational strategy. We directly tested this proposal by having males and females navigate in an "ambiguous" virtual Morris water maze environment that permitted participants to choose and use either an allocentric or an egocentric strategy. A novel probe trial at the end of training revealed which strategy each participant had been using and showed that the strategy selected by the greatest number of males and females was allocentric, and that this bias was even greater for females. Traditional measures of navigational performance (distance, latency, probe dwell time) indicated that overall, males were more efficient than females. However, this gender difference was not related to strategy choice: males were better than females regardless of strategy, though the difference was significant only in those navigating allocentrically. These data indicate that while males may navigate allocentrically more efficiently than females, this does not account for the male advantage in navigation. The data also indicate that under specific circumstances, females may also prefer and use an allocentric strategy to navigate. These findings have implications for theories regarding the differential use of the hippocampus by men and women. [ABSTRACT FROM AUTHOR]

Abstract: Successful navigation requires interactions among multiple but overlapping neural pathways mediating distinct capabilities, including egocentric (self-oriented, route-based) and allocentric (spatial, map-based) learning. Route-based navigation has been shown to be impaired following acute exposure to the dopaminergic (DA) drugs (+)-methamphetamine and (+)-amphetamine, but not the serotoninergic (5-HT) drugs (±)-3,4-methylenedioxymethamphetamine or (±)-fenfluramine. The dopaminergic-rich neostriatum is involved in both allocentric and egocentric navigation. This experiment tested whether dorsal striatal DA loss using bilateral 6-hydroxydopamine (6-OHDA) injections impaired one or both types of navigation. Two weeks following 6-OHDA injections, rats began testing in the Cincinnati water maze (CWM) followed by the Morris water maze (MWM) for route-based and spatial navigation, respectively. 6-OHDA treatment significantly increased latency and errors in the CWM and path length, latency, and cumulative distance in the MWM with no difference on cued MWM trials. Neostriatal DA levels were reduced by 80% at 2 and 7weeks post-treatment. In addition, 6-OHDA increased DA turnover and decreased norepinephrine (NE) levels. 6-OHDA injections did not alter monoamine levels in the prefrontal cortex. The data support that neostriatal DA modulates both types of navigation. [Copyright &y& Elsevier]

Abstract: Following brain injury, many patients experience egocentric spatial neglect, where they fail to respond to stimuli on the contralesional side of their body. On the other hand, allocentric, object-based neglect refers to the symptom of ignoring the contralesional side of objects, regardless of the objects’ egocentric position. There is an established tradition for considering these two phenomena as both behaviorally and anatomically dissociable. However, several studies and some theoretical work have suggested that these rather reflect two aspects of a unitary underlying disorder. Furthermore, in a recent large study reported that acute allocentric neglect is only observed in cases where substantial egocentric neglect is also present. In a new sample of right hemisphere stroke patients, we attempted to control for potential confounds by using a novel continuous measure for allocentric neglect (in addition to a recently developed continuous measure for egocentric neglect). Our findings suggest a strong association between egocentric and allocentric neglect. Consistent with the work of , we found allocentric behavioral deficits only in conjunction with egocentric deficits as well as a large corresponding overlap for the anatomical regions associated with egocentric and with allocentric neglect. We discuss how different anatomical and behavioral findings can be explained in a unified physiologically plausible framework, whereby allocentric and egocentric effects interact. [Copyright &y& Elsevier]

Humans demonstrate preferences to use egocentric or allocentric reference frames in navigation tasks that lack embodied (vestibular and/or proprioceptive) cues. Here, we investigated how reference frame proclivities affect spatial navigation in horizontal versus vertical planes. Point-to-origin performance after visually displayed vertical trajectories was surprisingly accurate and almost matched yaw performance for both egocentric and allocentric strategies. For vertical direction changes, 39% of participants unexpectedly switched to their non-preferred (allocentric) reference frame. This might be explained by vertical (25°–90° up/downward pitched) trajectories having lower ecological validity and creating more pronounced visuo-vestibular conflicts, emphasizing individual differences in processing idiothetic, embodied sensory information. [ABSTRACT FROM AUTHOR]

Comanagement success relies on the proper administration of resources and on the capacity of users to establish and maintain positive social relationships with multiple actors. We assessed multifunctional relationships of small-scale artisanal fisher organizations engaged in a coastal benthic resources comanagement system in Chile to explore bridging and linking social capital, using an egocentric network approach. The formal leaders of 38 small-scale fisher organizations were surveyed to investigate (1) similarities and differences in social capital among fisher organizations and regions, and (2) possible effects of social capital levels on comanagement performance. Results show that the best performing fisher organizations are those with higher levels of linking and bridging social capital. Positive and strong correlations exist between linking social capital levels and comanagement performance variables. Importantly, fisher organizations considered to manage resources successfully consistently presented high levels of linking social capital, irrespective of variability in bridging social capital. Using egocentric networks allows understanding actors' differences in the comanagement social structure, thus providing critical insights for improving comanagement systems. [ABSTRACT FROM AUTHOR]

The present study investigated the brain dynamics accompanying spatial navigation based on distinct reference frames. Participants preferentially using an allocentric or an egocentric reference frame navigated through virtual tunnels and reported their homing direction at the end of each trial based on their spatial representation of the passage. Task-related electroencephalographic (EEG) dynamics were analyzed based on independent component analysis (ICA) and subsequent clustering of independent components. Parietal alpha desynchronization during encoding of spatial information predicted homing performance for participants using an egocentric reference frame. In contrast, retrosplenial and occipital alpha desynchronization during retrieval covaried with homing performance of participants using an allocentric reference frame. These results support the assumption of distinct neural networks underlying the computation of distinct reference frames and reveal a direct relationship of alpha modulation in parietal and retrosplenial areas with encoding and retrieval of spatial information for homing behavior. [ABSTRACT FROM AUTHOR]

Abstract: We present a novel method of combining eye tracking with specially designed virtual environments to provide objective evidence of navigational strategy selection. A simple, inexpensive video camera with an easily built infrared LED array is used to capture eye movements at 60Hz. Simple algorithms analyze gaze position at the start of each virtual maze trial to identify stimuli used for navigational orientation. To validate the methodology, human participants were tested in two virtual environments which differed with respect to features usable for navigation and which forced participants to use one or another of two well-known navigational strategies. Because the environmental features for the two kinds of navigation were clustered in different regions of the environment (and the video display), a simple analysis of gaze-position during the first (i.e., orienting) second of each trial revealed which features were being attended to, and therefore, which navigational strategy was about to be employed on the upcoming trial. [Copyright &y& Elsevier]

Abstract: Estradiol treatment administered systemically or directly to the dorsolateral striatum across two days impairs performance on a response task in which rats learn to make a specific body turn to locate food on a maze. Estradiol can act through both slow and rapid signaling pathways to regulate learning impairments, however it is impossible to dissociate the slow from the rapid contributions of estradiol following long exposures. To assess the rapid effects of estradiol on striatum-sensitive learning, we trained rats on a response learning task after either relatively short or long treatments of estradiol infused directly into the striatum. Three-month-old female rats were ovariectomized 21days before training and received guide cannulae implanted bilaterally into the dorsolateral striatum. For short duration treatments, rats were given bilateral infusions (0.5μl) of 17β-estradiol-sulfate (0, 5, 50, or 500nM in aCSF-vehicle) either 2h or 15min prior to training. For long duration treatments, rats received a series of estradiol infusions (500nM) at 48, 24, and 2h prior to training. Replicating previous findings (Zurkovsky et al., 2007), intra-striatal estradiol treatments given for two days prior to training impaired response learning. Estradiol-induced impairments in performance were also demonstrated 2h, but not 15min, after single infusions. Thus, estradiol acts within hours of exposure in the striatum, a structure lacking classical estrogen receptors, to impair response learning. [Copyright &y& Elsevier]

This report addresses phylogenetic variation in a spatial skill that underlies tool use: aligning objects to a feature of a surface. Fragaszy and Cummins-Sebree's [Behavioral and Cognitive Neuroscience Reviews 4:282-306, 2005] model of relational spatial reasoning and Skill Development and Perception-Action theories guided the design of the study. We examined how capuchins and chimpanzees place stick objects of varying shapes into matching grooves on a flat surface. Although most individuals aligned the long axis of the object with the matching groove more often than expected by chance, all typically did so with poor precision. Some individuals managed to align a second feature, and only one (a capuchin monkey) achieved above-chance success at aligning three features with matching grooves. Our findings suggest that capuchins and chimpanzees do not reliably align objects along even one axis, and that neither species can reliably or easily master object placement tasks that require managing two or more spatial relations concurrently. Moreover, they did not systematically vary their behavior in a manner that would aid discovery of the affordances of the stick-surface combination beyond sliding the stick along the surface (which may have provided haptic information about the location of the groove). These limitations have profound consequences for the forms of tool use we can expect these individuals to master. Am. J. Primatol. 73:1012-1030, 2011. © 2011 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Abstract: This study investigates the relative contribution of body parts in the elaboration of a whole-body egocentric attraction phenomenon previously observed during earth-based judgments. This was addressed through a particular earth-based task requiring estimating the possibility of passing under a projected line, imagining a forward horizontal displacement. Different postural configurations were tested, involving whole-body tilt, trunk tilt alone or head tilt alone. Two legs positions relative to the trunk were manipulated. Results showed systematic deviations of the subjective “passability” toward the tilt, linearly related to the tilt magnitude. For each postural configuration, the egocentric influence appeared to be highly dependent on the position of trunk and head axes, whereas the legs position appeared not relevant. When compared to the whole-body tilt condition, tilting the trunk alone consistently reduced the amount of the deviation toward the tilt, whereas tilting the head alone consistently increased it. Our results suggest that several specific effects from multiple body parts can account for the global deviation of the estimates observed during whole-body tilt. Most importantly, we support that the relative contribution of the body segments could mainly depend on a reweighting process, probably based on the reliability of sensory information available for a particular postural set. [Copyright &y& Elsevier]

Map information for drivers is usually presented in an allocentric-topographic form (as with printed maps) or in an egocentric-schematic form (as with road signs). The advent of new variable message boards on UK motorways raises the possibility of presenting road maps to reflect congestion ahead. Should these maps be allocentric-topographic or egocentric-schematic? This was assessed in an eye tracking study, with participants viewing maps of a motorway network in order to identify whether any congestion was relevant to their intended route. The schematic-egocentric maps were responded to most accurately with shorter fixation durations suggesting easier processing. In particular, the driver's entrance and intended exit from the map were attended to more in the allocentric maps. Individual differences in mental rotation ability also seem to contribute to poor performance on allocentric maps. The results favour schematic-egocentric maps for roadside congestion information, but also provide theoretical insights into map-rotation and individual differences. Statement of Relevance: This study informs designers and policy makers about optimum representations of traffic congestion on roadside variable message signs and, furthermore, demonstrates that individual differences contribute to problems with processing certain sign types. Schematic-egocentric representations of a motorway network produced the best results, as noted in behavioural and eye movement measures. [ABSTRACT FROM AUTHOR]

Spatial priming allows memory for target locations to be evaluated, whereby when a target appears in the same location across trials, participants become more efficient at locating it and consequently their search times decrease. Previously, we reported priming effects when the location of a target was repeated with respect to the participant's body but not when it was repeated relative to their eye position; therefore, suggesting that body-centred information is available after a delay of at least a few seconds (Ball et al. in Exp Brain Res 204:585-594, ). However, we were unable to rule out the possibility that stable allocentric cues within the room may have contributed to the priming effects that we observed. In this current study, we introduced a condition where despite participants moving to a new location between trials, their position relative to the target was maintained. This movement disrupted any potential room-based cues about the target location. While we replicated our previous finding of priming when the location of the target was repeated relative to the viewer when no movement was required, we also found robust priming effects when participants moved to a new location in between trials. Thus, we provide clear evidence that in our spatial priming task, the location of the target was being coded in a body-centred reference frame and that this information is available after a delay. [ABSTRACT FROM AUTHOR]

Abstract: Patients with right hemisphere lesions often omit or misread words on the left side of a text or the initial letters of single words, a phenomenon termed neglect dyslexia (ND). Omissions of words on the contralesional side of the page are considered as egocentric or space-based errors, whereas misread words can be viewed as a type of stimulus-centered error where the left part of a single perceptual entity (the word) is neglected. Previous patient studies have shown that optokinetic stimulation (OKS) significantly modulates many facets of the neglect syndrome, including the subjective body midline, line bisection and size distortions. An open question is whether OKS can also influence omissions and stimulus-centered errors in paragraph reading in ND. The current study compared the influence of OKS on both types of reading errors using controlled indented paragraph reading tests in a group of 9 right-hemisphere lesioned patients with ND, 7 patients without ND and 9 matched healthy controls. Leftward OKS significantly reduced omissions on the left side of the text in ND. In contrast, the pattern of stimulus-centered reading errors remained unchanged. In conclusion egocentric manipulations like OKS only appear to influence space-based attentional processes evident as omissions in paragraph reading but have no impact on stimulus-centered attentional processes evident as word-based errors during paragraph reading in ND. [Copyright &y& Elsevier]

Cognitive neuroscience literature suggests a strong dissociation between the ability to mentally transform object and body stimuli (Hegarty & Waller, 2004). However, little is known about how this ability changes with age. This dissociation was explored in 20 younger (19-24 years) and 20 older (65-87 years) adults. Mental rotation of object stimuli was demonstrated for both age groups, suggesting that the neuro-cognitive network involved with performing (object-based) mental transformations is relatively preserved in older age. Compared to young adults, older adults displayed the greatest decline in performance efficiency for the whole-body task. The authors propose that an age-related decline in the integrity of body-schema information may account for this change. [ABSTRACT FROM AUTHOR]

Abstract: Patients with right hemisphere lesions often omit or misread words on the left side of a text or the beginning letters of single words which is termed neglect dyslexia (ND). Two types of reading errors are typically observed in ND: omissions and word-based reading errors. The prior are considered as space-based omission errors on the contralesional side of the page, while the latter can be viewed as a kind of stimulus- or word-based reading errors where leftsided parts of a single perceptual entity (the word) are neglected. The head, trunk and eyes are part of a hypothetical egocentric reference frame that is aligned around our body and divides space into a left and right hemispace. Previous neglect studies have shown that head- and trunk-orientation significantly influence contralesional neglect. An open question is whether such egocentric manipulations also influence omissions and word-based errors in paragraph reading in ND. The current study investigated in a sample of right-hemisphere lesioned patients with ND vs. without ND and matched healthy control subjects the influence of head-rotation (HR) on both types of reading errors using controlled indented paragraph reading tests. Passive leftward HR significantly reduced omission errors on the left side of the text in ND, but had no effect on word-based reading errors. In conclusion egocentric manipulations like HR only appear to influence space-based attentional processes in neglect evident as omissions in paragraph reading but have no impact on those attentional processes involved in word identification evident as word-based errors in paragraph reading. [ABSTRACT FROM AUTHOR]

Abstract: We studied the effect of static pitch body tilts on the perception of self-motion direction induced by a visual stimulus. Subjects were seated in front of a screen on which was projected a 3D cluster of moving dots visually simulating a forward motion of the observer with upward or downward directional biases (relative to a true earth horizontal direction). The subjects were tilted at various angles relative to gravity and were asked to estimate the direction of the perceived motion (nose-up, as during take-off or nose-down, as during landing). The data showed that body orientation proportionally affected the amount of error in the reported perceived direction (by 40% of body tilt magnitude in a range of ±20°) and these errors were systematically recorded in the direction of body tilt. As a consequence, a same visual stimulus was differently interpreted depending on body orientation. While the subjects were required to perform the task in a geocentric reference frame (i.e., relative to a gravity-related direction), they were obviously influenced by egocentric references. These results suggest that the perception of self-motion is not elaborated within an exclusive reference frame (either egocentric or geocentric) but rather results from the combined influence of both. [ABSTRACT FROM AUTHOR]

We review human functional neuroimaging studies that have explicitly investigated the reference frames used in different cortical regions for representing spatial locations of objects. Beyond the general distinction between 'egocentric' and 'allocentric' reference frames, we provide evidence for the selective involvement of the posterior parietal cortex and associated frontal regions in the specific process of egocentric localization of visual and somatosensory stimuli with respect to relevant body parts ('body referencing'). Similarly, parahippocampal and retrosplenial regions, together with specific parietal subregions such as the precuneus, are selectively involved in a specific form of allocentric representation in which object locations are encoded relative to enduring spatial features of a familiar environment ('environmental referencing'). We also present a novel functional magnetic resonance imaging study showing that these regions are selectively activated, whenever a purely perceptual spatial task involves an object which maintains a stable location in space during the whole experiment, irrespective of its perceptual features and its orienting value as a landmark. This effect can be dissociated from the consequences of an explicit memory recall of landmark locations, a process that further engages the retrosplenial cortex. [ABSTRACT FROM AUTHOR]

The hippocampus is crucial for both spatial navigation and episodic memory, suggesting that it provides a common function to both. Here we adapt a spatial paradigm, developed for rodents, for use with functional MRI in humans to show that activation of the right hippocampus predicts the use of an allocentric spatial representation, and activation of the left hippocampus predicts the use of a sequential egocentric representation. Both representations can be identified in hippocampal activity before their effect on behavior at subsequent choice-points. Our results suggest that, rather than providing a single common function, the two hippocampi provide complementary representations for navigation, concerning places on the right and temporal sequences on the left, both of which likely contribute to different aspects of episodic memory. [ABSTRACT FROM AUTHOR]

In two experiments we investigated the extent to which rats (Rattus norvegicus) use an egocentric trajectory and landmarks to locate a goal. In Experiment 1 we trained groups to locate the hidden platform in a water maze with either 1 of 3 or 3 of 3 predictive landmarks, and with either a random or fixed egocentric trajectory. A choice test revealed that regardless of the landmark configuration, rats relied on a directional, egocentric trajectory, when it was available, to locate the platform. In Experiment 2 we found that adding four predictive landmarks following training with a constant egocentric trajectory did not alter rats' initial attention to the trajectory. We conclude that the presence of nonpredictive landmarks in a predictive array did not affect the use of landmarks. With a blocking design, rats used initially an egocentric path, then landmarks. These results add to the notion that animals use available spatial cues sequentially. [ABSTRACT FROM AUTHOR]

Spatial priming in visual search is a well-documented phenomenon. If the target of a visual search is presented at the same location in subsequent trials, the time taken to find the target at this repeated target location is significantly reduced. Previous studies did not determine which spatial reference frame is used to code the location. At least two reference frames can be distinguished: an observer-related frame of reference (egocentric) or a scene-based frame of reference (allocentric). While past studies suggest that an allocentric reference frame is more effective, we found that an egocentric reference frame is at least as effective as an allocentric one (Ball et al. Neuropsychologia 47(6):1585–1591, ). Our previous study did not identify which specific egocentric reference frame was used for the priming: participants could have used a retinotopic or a body-centred frame of reference. Here, we disentangled the retinotopic and body-centred reference frames. In the retinotopic condition, the position of the target stimulus, when repeated, changed with the fixation position, whereas in the body-centred condition, the position of the target stimulus remained the same relative to the display, and thus to the body-midline, but was different relative to the fixation position. We used a conjunction search task to assess the generality of our previous findings. We found that participants relied on body-centred information and not retinotopic cues. Thus, we provide further evidence that egocentric information, and specifically body-centred information, can persist for several seconds, and that these effects are not specific to either a feature or a conjunction search paradigm. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper describes the challenge that different cultural beliefs about parenting pose for the practice of infant observation and direct clinical work. In particular it discusses the distinction between egocentric and socio-centric cultural views, how cultural presuppositions infuse our understanding and perception, and how hard it is not to judge others as a result of our own cultural beliefs and biases. [ABSTRACT FROM AUTHOR]

A conflict between an egocentric and an external reference frame can be highlighted by examining the marked deficit observed with tactile temporal order judgments (TOJ) when the hands are crossed. The anecdotally-reported large individual differences in the magnitude of this crossed-hands deficit were explored here by testing a large group of participants (48; 24 female). Given that females have been shown to be more visually dependent than males in the potentially related rod-and-frame test (RFT), we hypothesized that females would show a larger influence of the external reference frame (i.e., a larger crossed-hands deficit). As predicted, female participants produced larger tactile TOJ deficits compared to our male participants. We also administered the RFT in these participants with hands crossed and uncrossed. Crossing the hands increased the effect of the frame in the RFT, more so for females than males, further highlighting the potential difference in the way that each sex accommodates reference frame conflicts. Finally, examining the relation between the two tasks revealed a significant correlation, with larger frame effects associated with larger crossed-hands TOJ deficits, but this only held for males. We speculate that sex-specific differences in multisensory processing and spatial ability may explain why females are less able to disambiguate a crossed-hands posture than are males. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Insights into the functional nature and neuroanatomy of spatial attention have come from research in neglect patients but to date many conflicting results have been reported. The novelty of the current study is that we used voxel-wise analyses based on information from segmented grey and white matter tissue combined with diffusion tensor imaging to decompose neural substrates of different neglect symptoms. Allocentric neglect was associated with damage to posterior cortical regions (posterior superior temporal sulcus, angular, middle temporal and middle occipital gyri). In contrast, egocentric neglect was associated with more anterior cortical damage (middle frontal, postcentral, supramarginal, and superior temporal gyri) and damage within subcortical structures. Damage to intraparietal sulcus (IPS) and the temporo-parietal junction (TPJ) was associated with both forms of neglect. Importantly, we showed that both disorders were associated with white matter lesions suggesting damage within long association and projection pathways such as the superior longitudinal, superior fronto-occipital, inferior longitudinal, and inferior fronto-occipital fascicule, thalamic radiation, and corona radiata. We conclude that distinct cortical regions control attention (a) across space (using an egocentric frame of reference) and (b) within objects (using an allocentric frame of reference), while common cortical regions (TPJ, IPS) and common white matter pathways support interactions across the different cortical regions. [ABSTRACT FROM AUTHOR]

Abstract: Path integration is a navigation strategy widely observed in nature where an animal maintains a running estimate, called the home vector, of its location during an excursion. Evidence suggests it is both ancient and ubiquitous in nature, and has been studied for over a century. In that time, canonical and neural network models have flourished, based on a wide range of assumptions, justifications and supporting data. Despite the importance of the phenomenon, consensus and unifying principles appear lacking. A fundamental issue is the neural representation of space needed for biological path integration. This paper presents a scheme to classify path integration systems on the basis of the way the home vector records and updates the spatial relationship between the animal and its home location. Four extended classes of coordinate systems are used to unify and review both canonical and neural network models of path integration, from the arthropod and mammalian literature. This scheme demonstrates analytical equivalence between models which may otherwise appear unrelated, and distinguishes between models which may superficially appear similar. A thorough analysis is carried out of the equational forms of important facets of path integration including updating, steering, searching and systematic errors, using each of the four coordinate systems. The type of available directional cue, namely allothetic or idiothetic, is also considered. It is shown that on balance, the class of home vectors which includes the geocentric Cartesian coordinate system, appears to be the most robust for biological systems. A key conclusion is that deducing computational structure from behavioural data alone will be difficult or impossible, at least in the absence of an analysis of random errors. Consequently it is likely that further theoretical insights into path integration will require an in-depth study of the effect of noise on the four classes of home vectors. [Copyright &y& Elsevier]

Recent research development on egocentric social network analysis focuses on the causes and consequences of relationships among sets of people rather than on the features, attribute data of individuals, and their basic database operations. This work describes a record type of network data model that would be suitable to perform database operations in social network analysis (SNA). It describes two schemas that would be needed for web space interface and database operations. A force directed algorithm was used to display membership vertices that show link membership number, name, and pictures. A Breadth first search algorithm was then embedded in the algorithm to avoid endless searching in cycled nodes. Measurement of degree of centrality, betweenness, and closeness was incorporated to determine the relationship among the nodes and their linkages. Implementation of database operations into SNA reveals not only social information but also critical economic reports of the individuals. Observation of the work showed that users can impose any relevant query related to the defined schemas and the results would be available to monitor both social and economic activities of the memberships. [ABSTRACT FROM AUTHOR]

Abstract: Neural resources subserving spatial processing in either egocentric or allocentric reference frames are, at least partly, dissociated. However, it is unclear whether these two types of representations are independent or whether they interact. We investigated this question using a learning transfer paradigm. The experiment and material were designed so that they could be used in a clinical setting. Here, we tested healthy subjects in an imagined viewer-rotation task and an imagined object-rotation task. The order of the tasks was counterbalanced across subjects. The results showed that subjects who did the viewer-rotation task first had fewer errors and shorter latencies of response in the object-rotation task, whereas subjects who did the object-rotation task first had little if any advantage in the viewer-rotation task. In other words, the results revealed an asymmetric learning transfer between tasks, which suggests that spatial representations are hierarchically organized. Specifically, the results indicate that the viewer-rotation task engaged allocentric representations and egocentric representations, whereas the object-rotation task engaged only egocentric representations. [Copyright &y& Elsevier]

Abstract: The hippocampus has been implicated in aspects of spatial memory. Its ability to generate new neurons has been suggested to play a role in memory formation. Hippocampal serotonin (5-HT) neurotransmission has also been proposed as a contributor to memory processing. Studies have shown that the 5-HT7 receptor is present in the hippocampus in relatively high abundance. Thus the aim of the present study was to investigate the possible role of the 5-HT7 receptor in spatial memory using 5-HT7 receptor-deficient mice (5-HT7 −/−). A hippocampus-associated spatial memory deficit in 5-HT7 −/− mice was demonstrated using a novel location/novel object test. A similar reduction in novel location exploration was observed in C57BL/6J mice treated with the selective 5-HT7 receptor antagonist SB-269970. These findings prompted an extended analysis using the Barnes maze demonstrating that 5-HT7 −/− mice were less efficient in accommodating to changes in spatial arrangement than 5-HT7 +/+ mice. 5-HT7 −/− mice had specific impairments in memory compilation required for resolving spatial tasks, which resulted in impaired allocentric spatial memory whereas egocentric spatial memory remained intact after the mice were forced to switch back from striatum-dependent egocentric to hippocampus-dependent allocentric memory. To further investigate the physiological bases underlining these behaviors we compared hippocampal neurogenesis in 5-HT7 +/+ and 5-HT7 −/− mice employing BrdU immunohistochemistry. The rate of cell proliferation in the dentate gyrus was identical in the two genotypes. From the current data we conclude that the 5-HT7 −/− mice performed by remembering a simple sequence of actions that resulted in successfully locating a hidden target in a static environment. [Copyright &y& Elsevier]

Abstract: Mounting evidence indicates that the retrosplenial cortex (RSP) has a critical role in spatial navigation. The goal of the present study was to characterize the specific nature of spatial memory deficits that are observed following damage to RSP. Rats with RSP lesions or sham lesions were first trained in a working memory task using an 8-arm radial arm maze. Rats were allowed 5min to visit each arm and retrieve food pellets and a 5-s delay was imposed between arm choices. Consistent with previous research, rats with RSP damage committed more errors than controls. In particular, RSP-lesioned rats committed more errors of omission (failing to visit an arm of the maze), but there were no lesion effects on errors of commission (revisiting an arm). Neither group of rats exhibited a turn bias (i.e., always turning a certain direction when choosing an arm). At the end of the training phase of the experiment, both groups had reached asymptote and committed very few errors. In the subsequent test phase, a longer delay (30-s) was imposed during some sessions. Both control and RSP-lesioned rats continued to make few errors during sessions with the standard 5-s delay, but RSP-lesioned rats were impaired at the 30-s delay and committed more errors of commission, consistent with an increase in taxing spatial working memory. [Copyright &y& Elsevier]

Abstract: We have previously shown the visual form agnosic patient D.F. has spared sensorimotor utilization of visual information relative to her poor perceptual processing of the same stimulus attributes. Her visuomotor skills are, however, only normal when egocentric visual coding can be used in the task. In other words, her egocentric sensorimotor processing is intact while her ‘allocentric’ coding of spatial position is impaired. The current investigation extends these previous observations by comparing D.F.’s performance in bimanual pointing to pairs of stimuli directly (the egocentric task) versus pointing to the homologous positions on an adjacent workspace (pantomimed reaching, the allocentric task). The results showed greatly superior pointing accuracy in direct pointing compared to pantomimed pointing. The mechanisms supporting her limited but remaining sensitivity to spatial relationships during pantomimed pointing remain unknown. These residual skills may reflect partially spared categorical coding and/or internal sensorimotor self-cueing. [Copyright &y& Elsevier]

Spatial cognition studies have described two main cognitive strategies involved in the memorization of traveled paths in human navigation. One of these strategies uses the action-based memory (egocentric) of the traveled route or paths, which involves kinesthetic memory, optic flow, and episodic memory, whereas the other strategy privileges a survey memory of cartographic type (allocentric). Most studies have dealt with these two strategies separately, but none has tried to show the interaction between them in spite of the fact that we commonly use a map to imagine our journey and then proceed using egocentric navigation. An interesting question is therefore: how does prior allocentric knowledge of the environment affect the egocentric, purely kinesthetic navigation processes involved in human navigation? We designed an experiment in which blindfolded subjects had first to walk and memorize a path with kinesthetic cues only. They had previously been shown a map of the path, which was either correct or distorted (consistent shrinking or growing). The latter transformations were studied in order to observe what influence a distorted prior knowledge could have on spatial mechanisms. After having completed the first learning travel along the path, they had to perform several spatial tasks during the testing phase: (1) pointing towards the origin and (2) to specific points encountered along the path, (3) a free locomotor reproduction, and (4) a drawing of the memorized path. The results showed that prior cartographic knowledge influences the paths drawn and the spatial inference capacity, whereas neither locomotor reproduction nor spatial updating was disturbed. Our results strongly support the notion that (1) there are two independent neural bases underlying these mechanisms: a map-like representation allowing allocentric spatial inferences, and a kinesthetic memory of self-motion in space; and (2) a common use of, or a switching between, these two strategies is possible. Nevertheless, allocentric representations can emerge from the experience of kinesthetic cues alone. [ABSTRACT FROM AUTHOR]

Abstract: Two experiments are reported that were designed to measure the accuracy and reliability of both visually guided hand movements (Exp. 1) and perceptual matching judgments (Exp. 2). The specific procedure for informing subjects of the required response on each trial was manipulated so that some tasks could only be performed using an allocentric representation of the visual target; others could be performed using either an allocentric or hand-centered representation; still others could be performed based on an allocentric, hand-centered or head/eye-centered representation. Both head/eye and hand centered representations are egocentric because they specify visual coordinates with respect to the subject. The results reveal that accuracy and reliability of both motor and perceptual responses are highest when subjects direct their response towards a visible target location, which allows them to rely on a representation of the target in head/eye-centered coordinates. Systematic changes in averages and standard deviations of responses are observed when subjects cannot direct their response towards a visible target location, but have to represent target distance and direction in either hand-centered or allocentric visual coordinates instead. Subjects’ motor and perceptual performance agree quantitatively well. These results strongly suggest that subjects process head/eye-centered representations differently from hand-centered or allocentric representations, but that they process visual information for motor actions and perceptual judgments together. [Copyright &y& Elsevier]