Cortical Correlates of Visuospatial Switching Processes Between Egocentric and Allocentric Frames of Reference: A fNIRS Study.

Human beings represent spatial information according to egocentric (body-to-object) and allocentric (object-to-object) frames of reference. In everyday life, we constantly switch from one frame of reference to another in order to react effectively to the specific needs of the environment and task demands. However, to the best of our knowledge, no study to date has investigated the cortical activity of switching and non-switching processes between egocentric and allocentric spatial encodings. To this aim, a custom-designed visuo-spatial memory task was administered and the cortical activities underlying switching vs non-switching spatial processes were investigated. Changes in concentrations of oxygenated and deoxygenated haemoglobin were measured using functional near-infrared spectroscopy (fNIRS). Participants were asked to memorize triads of geometric objects and then make two consecutive judgments about the same triad. In the non-switching condition, both spatial judgments considered the same frame of reference: only egocentric or only allocentric. In the switching condition, if the first judgment was egocentric, the second one was allocentric (or vice versa). The results showed a generalized activation of the frontal regions during the switching compared to the non-switching condition. Additionally, increased cortical activity was found in the temporo-parietal junction during the switching condition compared to the non-switching condition. Overall, these results illustrate the cortical activity underlying the processing of switching between body position and environmental stimuli, showing an important role of the temporo-parietal junction and frontal regions in the preparation and switching between egocentric and allocentric reference frames.

Neuropsychology of posteromedial parietal cortex and conversion factors from Mild Cognitive Impairment to Alzheimer's disease: systematic search and state-of-the-art review.

In the present review, we discuss the rationale and the clinical implications of assessing visuospatial working memory (VSWM), awareness of memory deficits, and visuomotor control in patients with mild cognitive impairment (MCI). These three domains are related to neural activity in the posteromedial parietal cortex (PMC) whose hypoactivation seems to be a significant predictor of conversion from MCI to Alzheimer's disease (AD) as indicated by recent neuroimaging evidence. A systematic literature search was performed up to May 2021. Forty-eight studies were included: 42 studies provided analytical cross-sectional data and 6 studies longitudinal data on conversion rates. Overall, these studies showed that patients with MCI performed worse than healthy controls in tasks assessing VSWM, awareness of memory deficits, and visuomotor control; in some cases, MCI patients' performance was comparable to that of patients with overt dementia. Deficits in VSWM and metamemory appear to be significant predictors of conversion. No study explored the relationship between visuomotor control and conversion. Nevertheless, it has been speculated that the assessment of visuomotor abilities in subjects at high AD risk might be useful to discriminate patients who are likely to convert from those who are not. Being able to indirectly estimate PMC functioning through quick and easy neuropsychological tasks in outpatient settings may improve diagnostic and prognostic accuracy, and therefore, the quality of the MCI patient's management.

Hand movements in Mild Cognitive Impairment: clinical implications and insights for future research.

Decreased upper-extremity/visuomotor abilities are frequently encountered in healthy aging. However, few studies have assessed hand movements in the prodromal stage of dementia. The evaluation of visuomotor skills in patients with Mild Cognitive Impairment (PwMCI) may have non-negligible clinical relevance both in diagnostic and prognostic terms, given the strong relationships with executive functioning and functional autonomies. In the present review paper, these issues will be disclosed by describing general pathophysiological and neuropsychological mechanisms responsible for visuomotor deficits, and by reporting the available experimental results on differences in visuomotor functioning between PwMCI, healthy controls and/or patients with dementia. Moreover, the relationships binding visuomotor and executive domains to functional autonomies will be then addressed. Finally, we will propose insights for future research.

Can I put myself in your shoes? Sharing peripersonal space reveals the simulation of the action possibilities of others.

The representation of the reachable space near the body or peripersonal space (PPS) plays an important role in action with objects and interaction with other people. Here we explored whether the representation of other people's PPS involves a simulation of their action possibility depending on the distance between the observer's body and the other person. We hypothesized that a simulation of action possibilities of others should be activated when they share the PPS of observers. In two experiments using Immersive Virtual Reality, the avatars were shown with their arms free or blocked (motor interference) at a reachable (i.e., Near/shared PPS) or not-reachable (i.e., Far/not-shared PPS) distance by the participants. Participants had to locate a glass in relation to the midline of the avatar's body, i.e., assuming the perspective of the avatar. To directly compare the representation of one's own and others' PPS, in Experiment 1 participants had to locate the glass in relation to themselves with their arms free or blocked. The glass was always within the PPS of either participants or avatars. The results showed that the localization of the glass from the avatar's perspective was slower with the blocked than free arm only when the avatar was in the near shared PPS, similar to the localization from one's own first-person perspective. Instead, there was no effect of motor interference in the far, not-shared PPS. This suggests that the representation of other people's PPS can involve motor simulation mechanisms when we share a common peripersonal area.

Spatial text processing: are estimates of time and distance influenced by the age of characters and readers?

It is widely accepted that, while hearing or reading a story, people continuously form and update mental representations of the characters, places and events being described, based on plausible spatial, temporal or intentional details. According to the embodied cognition approach, the mental representations that accompany text reading are grounded in each reader's own sensorimotor experiences. Two experiments were conducted to examine whether readers' estimates of time and distance are influenced by age, their own and that of the character being described. In Experiment 1, 182 young adults read the description of a route in a town being covered by a young or an elderly character. In Experiment 2, the same descriptions as in Experiment 1 were read by 121 young adults and 53 older people. To avoid a possible confound, a follow-up to Experiment 1 (Experiment 1a) repeated the study by removing from texts the adverbs describing the walking speed of characters. In all experiments, participants were asked to estimate: (a) the time the characters took to reach their destinations (time estimation task); and (b) the distance they covered (distance estimation task). The results showed that both characters' and readers' ages influenced the time estimated, whereas no effects were found on estimates of distance: the elderly character was estimated to take longer than the young character (Experiments 1, 1a and 2), and older readers estimated longer times than younger readers (Experiment 2). This prompts the conclusion that personal features of both the readers and the characters they read about were used to infer the temporal dimension of situations described in the narratives. The theoretical implications of the findings are discussed.

The role of mental imagery in pantomimes of actions towards and away from the body.

This study aimed to explore the relationship between action execution and mental rotation modalities. To this end, pantomime gesture (i.e. the mime of the use of an object) was used as its execution relies on imagery processes. Specifically, we tried to clarify the role of visuo-spatial or motor and body-related mental imagery processes in pantomime gestures performed away (AB, e.g. drawing on a sheet) and towards the body (TB, e.g. brushing the teeth). We included an "actual use" condition in which participants were asked to use a toothbrush and make 3, 6, or 9 circular movements close to their mouth (as if they were brushing their teeth) or to use a pencil and make 3, 6, or 9 circular movements on a desk (as if they were drawing circles). Afterwards, participants were asked to pantomime the actual use of the same objects ("pantomime" condition). Finally, they were asked to mentally rotate three different stimuli: hands, faces, and abstract lines. Results showed that participants were faster in AB than TB pantomimes. Moreover, the more accurate and faster the mental rotation of body-related stimuli was, the more similar the temporal duration between both kinds of pantomimes and the actual use of the objects appeared. Instead, the temporal similarity between AB pantomimes and pencil actual use, as well as, the duration of AB pantomime and actual use, were associated with the ability to mentally rotate abstract lines. This was not true for TB movements. These results suggest that the execution of AB and TB pantomimes may involve different mental imagery modalities. Specifically, AB pantomimes would not only require to mentally manipulate images of body-parts in movement but also represent the spatial relations of the object with the external world.

Congenital blindness limits allocentric to egocentric switching ability.

Many everyday spatial activities require the cooperation or switching between egocentric (subject-to-object) and allocentric (object-to-object) spatial representations. The literature on blind people has reported that the lack of vision (congenital blindness) may limit the capacity to represent allocentric spatial information. However, research has mainly focused on the selective involvement of egocentric or allocentric representations, not the switching between them. Here we investigated the effect of visual deprivation on the ability to switch between spatial frames of reference. To this aim, congenitally blind (long-term visual deprivation), blindfolded sighted (temporary visual deprivation) and sighted (full visual availability) participants were compared on the Ego-Allo switching task. This task assessed the capacity to verbally judge the relative distances between memorized stimuli in switching (from egocentric-to-allocentric: Ego-Allo; from allocentric-to-egocentric: Allo-Ego) and non-switching (only-egocentric: Ego-Ego; only-allocentric: Allo-Allo) conditions. Results showed a difficulty in congenitally blind participants when switching from allocentric to egocentric representations, not when the first anchor point was egocentric. In line with previous results, a deficit in processing allocentric representations in non-switching conditions also emerged. These findings suggest that the allocentric deficit in congenital blindness may determine a difficulty in simultaneously maintaining and combining different spatial representations. This deficit alters the capacity to switch between reference frames specifically when the first anchor point is external and not body-centered.

The effect of facial expressions on peripersonal and interpersonal spaces.

Identifying individuals' intent through the emotional valence conveyed by their facial expression influences our capacity to approach-avoid these individuals during social interactions. Here, we explore if and how the emotional valence of others' facial expressiveness modulates peripersonal-action and interpersonal-social spaces. Through Immersive Virtual Reality, participants determined reachability-distance (for peripersonal space) and comfort-distance (for interpersonal space) from male/female virtual confederates exhibiting happy, angry and neutral facial expressions while being approached by (passive-approach) or walking toward (active-approach) them. Results showed an increase of distance when seeing angry rather than happy confederates in both approach conditions of comfort-distance. The effect also appeared in reachability-distance, but only in the passive-approach. Anger prompts avoidant behaviors, and thus an expansion of distance, particularly with a potential violation of near body space by an intruder. Overall, the findings suggest that peripersonal-action space, in comparison with interpersonal-social space, is similarly sensitive to the emotional valence of stimuli. We propose that this similarity could reflect a common adaptive mechanism shared by these spaces, presumably at different degrees, for ensuring self-protection functions.

Perception of Peripersonal and Interpersonal Space in Patients with Restrictive-type Anorexia.

This study examines whether the perception of peripersonal action-space and interpersonal social-space is modified in patients with restrictive-type anorexia in two experimental conditions using videos. First, participants stopped the video of an approaching stimulus when they felt the distance to be comfortable for interacting with it (first-person perspective). Second, participants stopped the video when an observed individual approaching a stimulus, or being approached by it, was at a comfortable distance (third-person perspective). In the first-person perspective, the results showed an estimation of peripersonal space that did not differ from controls when an object was approaching and an increase in interpersonal space compared with controls when a male or female individual was approaching. In the third-person perspective, both individual-object and individual-individual distances were larger in anorexic patients. These results indicate a specific deficit in adjusting interpersonal distances in both the first-person and third-person perspectives. Copyright © 2017 John Wiley & Sons, Ltd and Eating Disorders Association.

Frames of reference and categorical/coordinate spatial relations in a "what was where" task.

The aim of this study was to explore how people use egocentric (i.e., with respect to their body) and allocentric (i.e., with respect to another element in the environment) references in combination with coordinate (metric) or categorical (abstract) spatial information to identify a target element. Participants were asked to memorize triads of 3D objects or 2D figures, and immediately or after a delay of 5 s, they had to verbally indicate what was the object/figure: (1) closest/farthest to them (egocentric coordinate task); (2) on their right/left (egocentric categorical task); (3) closest/farthest to another object/figure (allocentric coordinate task); (4) on the right/left of another object/figure (allocentric categorical task). Results showed that the use of 2D figures favored categorical judgments over the coordinate ones with either an egocentric or an allocentric reference frame, whereas the use of 3D objects specifically favored egocentric coordinate judgments rather than the allocentric ones. Furthermore, egocentric judgments were more accurate than allocentric judgments when the response was Immediate rather than delayed and 3D objects rather than 2D figures were used. This pattern of results is discussed in the light of the functional roles attributed to the frames of reference and spatial relations by relevant theories of visuospatial processing.

Development of egocentric and allocentric spatial representations from childhood to elderly age.

Spatial reference frames are fundamental to represent the position of objects or places. Although research has reported changes in spatial memory abilities during childhood and elderly age, no study has assessed reference frames processing during the entire lifespan using the same task. Here, we aimed at providing some preliminary data on the capacity to process reference frames in 283 healthy participants from 6 to 89 years of age. A spatial memory task requiring egocentric/allocentric verbal judgments about objects in peri-/extrapersonal space was used. The main goals were: (1) tracing a baseline of the normal process of development of these spatial components; (2) clarifying if reference frames are differently vulnerable to age-related effects. Results showed a symmetry between children of 6-7 years and older people of 80-89 years who were slower and less accurate than all other age groups. As regards processing time, age had a strong effect on the allocentric component, especially in extrapersonal space, with a longer time in 6- to 7-year-old children and 80- to 89-year-old adults. The egocentric component looked less affected by aging. Regarding the level of spatial ability (accuracy), the allocentric ability appeared less sensitive to age-related variations, whereas the egocentric ability progressively improved from 8 years and declined from 60 years. The symmetry in processing time and level of spatial ability is discussed in relation to the development of executive functions and to the structural and functional changes due to incomplete maturation (in youngest children) and deterioration (in oldest adults) of underlying cerebral areas.

The influence of anxiety and personality factors on comfort and reachability space: a correlational study.

Although the effects of several personality factors on interpersonal space (i.e. social space within personal comfort area) are well documented, it is not clear whether they also extend to peripersonal space (i.e. reaching space). Indeed, no study has directly compared these spaces in relation to personality and anxiety factors even though such a comparison would help to clarify to what extent they share similar mechanisms and characteristics. The aim of the present paper was to investigate whether personality dimensions and anxiety levels are associated with reaching and comfort distances. Seventy university students (35 females) were administered the Big Five Questionnaire and the State-Trait Anxiety Inventory; afterwards, they had to provide reachability- and comfort-distance judgments towards human confederates while standing still (passive) or walking towards them (active). The correlation analyses showed that both spaces were positively related to anxiety and negatively correlated with the Dynamism in the active condition. Moreover, in the passive condition higher Emotional Stability was related to shorter comfort distance, while higher cognitive Openness was associated with shorter reachability distance. The implications of these results are discussed.

Flanker interference effects in a line bisection task.

Previous studies have shown that flanking distractors influence line bisection. In the present study, we examined if reaching the flanker after bisecting the line resulted in a variation of flanker interference on line bisection. Right- and left-handed participants were asked to bisect a horizontal line flanked by a dot (bisection task, B-task) or to bisect the line and then to reach the dot (bisection plus reaching task, BR-task). The dot was placed laterally to, and above or below, the line edge. The results showed that in both tasks the subjective midpoint was shifted away from the position of the dot. However, this effect was greater in the BR-task than in the B-task. We suggest that the requirement to perform an action to the flanker in the BR-task induced participants to pay more attention to the dot, enhancing its salience and distorting effects on line bisection.

Who is speaking? Implicit and explicit self and other voice recognition.

In the domain of self-recognition, voice is a critical feature for self/other distinction. The aim of this study was to explore if people have an implicit and/or explicit knowledge of their voice. A group of healthy participants were submitted to an implicit and an explicit self-voice recognition task. They listened to pairs of pre-recorded auditory stimuli (words or pseudowords) pronounced by themselves, by a familiar or an unfamiliar person. Afterwards, in the "Implicit task" participants had to judge whether the pair of stimuli were pronounced by same or different speakers; in the "Explicit task" they had to identify if one of the stimuli was or not their own voice. Results showed a difference between Implicit and Explicit tasks since participants were more accurate in implicit than explicit self voice-recognition. Moreover, in the Implicit task, participants had the same level of accuracy when they had to judge stimuli pronounced with self or others' voice, whereas when an explicit voice-recognition was required, they were less accurate with self than with others' voice.

Spatial representations of objects used away and towards the body: The effect of near and far space.

An action with an object can be accomplished only if we encode the position of the object with respect to our body (i.e., egocentrically) and/or to another element in the environment (i.e., allocentrically). However, some actions with the objects are directed towards our body, such as brushing our teeth, and others away from the body, such as writing. Objects can be near the body, that is within arm reaching, or far from the body, that is outside arm reaching. The aim of this study was to verify if the direction of use of the objects influences the way we represent their position in both near and far space. Objects typically used towards (TB) or away from the body (AB) were presented in near or far space and participants had to judge whether an object was closer to them (i.e., egocentric judgement) or closer to another object (i.e., allocentric judgement). Results showed that egocentric judgements on TB objects were more accurate in near than in far space. Moreover, allocentric judgements on AB objects were less accurate than egocentric judgements in near space but not in far space. These results are discussed with respect to the different roles that visuo-motor and visuo-spatial mechanisms play in near space and far space, respectively.

Interaction with Virtual Humans and Effect of Emotional Expressions: Anger Matters!

Today we are experiencing a hybrid real-virtual society in which the interaction with virtual humans is normal and "quasi-social". Understanding the way we react to the interaction with virtual agents and the impact of emotions on social dynamics in the virtual world is fundamental. Therefore, in this study we investigated the implicit effect of emotional information by adopting a perceptual discrimination task. Specifically, we devised a task that explicitly required perceptual discrimination of a target while involving distance regulation in the presence of happy, neutral, or angry virtual agents. In two Immersive Virtual Reality experiments, participants were instructed to discriminate a target on the virtual agents' t-shirts, and they had to provide the response by stopping the virtual agents (or themselves) at the distance where they could identify the target. Thus, facial expressions were completely irrelevant to the perceptual task. The results showed that the perceptual discrimination implied a longer response time when t-shirts were worn by angry rather than happy or neutral virtual agents. This suggests that angry faces interfered with the explicit perceptual task people had to perform. From a theoretical standpoint, this anger-superiority effect could reflect an ancestral fear/avoidance mechanism that prompts automatic defensive reactions and bypasses other cognitive processes.

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.

Psychological Reactions during and after a Lockdown: Self-Efficacy as a Protective Factor of Mental Health.

The aim of the present study was to investigate the effects of home confinement/social isolation (i.e., lockdown), imposed to reduce large-scale spread of a disease in the population, on the mental health of individuals. Through an online survey during the lockdown (DL) related to COVID-19 (1085 respondents, 627 females, agerange: 18-82) (Italy, 23 April-2 May 2020), we revealed that situational factors, i.e., the presence of children at home and female gender, and psychological factors, i.e., a greater sense of isolation, lower perception of safety outside the home and higher trait anxiety, predicted higher levels of state anxiety (R2 = 0.58). The same factors, but with young age instead of the presence of children, predicted higher levels of perceived stress (R2 = 0.63). Then, these data were compared with those collected after the lockdown (AL) (174 respondents, 128 females, agerange: 19-78) (Italy, 1 July-31 October 2021). The results showed that along with a reduced sense of isolation (DL = 2.90 vs. AL = 2.10) and an increased perception of safety outside the home (DL = 2.63 vs. AL = 3.05), a reduction in state anxiety (DL = 45.76 vs. AL= 40.88) and stress appeared (DL = 18.84 vs. AL = 17.63). However, the situation was better for men than for women. Perceived self-efficacy emerged as a protective factor for mental health (R2range: 0.03-0.27). The results are discussed in light of the evidence on the effects of lockdown on individuals worldwide. These results may be used to make more educated decisions on targeted help for individuals who may be most adversely affected by the adoption of lockdowns in the future.

Embodied perception of reachable space: how do we manage threatening objects?

This study aimed at determining whether the size of reachable space is affected by the level of danger of some everyday manipulable objects. Two possibilities are examined: Dangerous objects affect the size of reachable space because of long-term semantic knowledge of their potential hurtful value or the on-line relation between objects' dangerous attributes and the body. The experimental paradigm combined the danger value (dangerous/not dangerous) and the orientation of objects (e.g. pointing away from/towards the perceiver). Reachability judgments measured the size of peripersonal space, and perception of objects' danger was estimated through questionnaires. Results revealed that, whatever the estimated level of objects' danger, the extent of peripersonal space was reduced when the threatening part of dangerous objects was oriented towards participants, not when oriented away. This suggests that the characteristics of the here and now body-objects interaction are crucial in affecting the boundary of peripersonal space.

Egocentric/allocentric and coordinate/categorical haptic encoding in blind people.

In this research, the impact of visual experience on the capacity to use egocentric (body-centered) and allocentric (object-centered) representations in combination with categorical (invariant non-metric) and coordinate (variable metric) spatial relations was examined. Participants memorized through haptic (congenitally blind, adventitiously blind, and blindfolded) and haptic + visual (sighted) exploration triads of 3D objects and then they were asked to judge: "which object was closest/farthest to you?" (egocentric-coordinate); "which object was on your left/right?" (egocentric-categorical); "which object was closest/farthest to a target object (e.g., cone)?" (allocentric-coordinate); "which object was on the left/right of the target object (e.g., cone)?" (allocentric-categorical). The results showed a slowdown in processing time when congenitally blind people provided allocentric-coordinate judgments and adventitiously blind people egocentric-categorical judgments. Moreover, in egocentric judgments, adventitiously blind participants were less accurate than sighted participants. However, the overall performance was quite good and this supports the idea that the differences observed are more quantitative than qualitative. The theoretical implications of these results are discussed.