Influence of different palatal morphologies on the accuracy of intraoral scanning of the edentulous maxilla: A three-dimensional analysis.

PURPOSE: This study investigated the influence of different palatal morphologies on the accuracy of intraoral scanning (TRIOS 4) of edentulous maxillae. METHODS: Six typodonts were fabricated for different palatal morphologies with flat (F), medium (M), and deep (D) palates, with palatal wrinkles (W), or smooth palates (S), resulting in six groups: WF, WM, WD and SF, SM, SD. Ten scans were performed for each group; standard tessellation language files obtained were imported into a software to measure trueness and precision in micrometer. Trueness was calculated as the mean of the standard deviation values obtained by superimposing each scan onto the reference scan. Precision was achieved by overlapping each scan with that with the best trueness in the group. Descriptive and post-hoc analyses were conducted. RESULTS: The mean values for trueness were as follows: WM=48.7±4.7, WD=161.7±18.4, WF=85.9±16, SM=48.1±2.4, SD=349.9±8.8, and SF=349.1±25.5. The precision values were as follows: WM=46.7±7.3, WD=46.9±9, WF=48.9±6.7, SM=46±2.7, SD=105.9±17.4, SF=72.6±10.8. Significant differences were observed for trueness between SM and SD (P < 0.001), SM and SF (P < 0.001), and WF and SF (P = 0.003); whereas for precision, significant differences were reported between WD and SD (P = 0.015). Regarding trueness and precision, no difference was found between WM and SM (P = 1.0). CONCLUSIONS: Medium palatal depth showed the best accuracy. The mean accuracy values were within the clinical acceptability thresholds for all palatal morphologies. The presence of rugae improved the precision of deeper palates and the trueness of flat palates. No differences were observed in the medium palates with or without rugae.

Trueness and precision of an intraoral scanner on abutments with subgingival vertical margins: An in vitro study.

OBJECTIVES: This study aimed to evaluate the accuracy of an intraoral scanner (IOS - Medit i700) on tooth abutments with vertical preparations at 2 depths below the free gingival margin, and to determine if the IOS can reproduce the area beyond the finish surface of the tested preparation geometry. METHODS: Two abutments for a maxillary first molar were designed by means of CAD software, with vertical preparations set at 1 and 2 mm below the gingiva. These abutments were subsequently printed in resin and placed on a reference model. The reference files consisted of scans made using a metrological machine on these abutments. Ten scans were made with the tested IOS on each sample, resulting in two study groups. The scans from the experimental groups were labeled "V-1″ for vertical preparation at 1 mm below the gingival margin and "V-2″ for 2 mm below. The analysis of these scans was performed using Geomagic Control X (3D SYSTEMS) to assess their trueness and precision in µm. Descriptive statistics with a 95 % confidence interval were employed, alongside independent sample tests, to ascertain any differences between the groups (α=0.05). RESULTS: Statistically significant differences were not found both for trueness (p=.104) and precision (p=.409), between the tested geometries. The mean values for trueness were V-1 = 37.5[31.4-43.6]; V-2 = 32.6[30.6-34.6]. About the precision, the mean values were V-1 = 20.5[8.4-32.5]; V-2 = 18.4[8.2-28.5]. In both the study groups, it was possible to detect the surface beyond the finish area. CONCLUSIONS: Within the limitations of this study, vertical preparation design allows for registration of the tooth anatomy beyond the finish area with IOS. Moreover, the mean accuracy values were clinically acceptable at both 1 and 2 mm below the gingival margin.

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.

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.

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.

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.

Social Context and Tool Use Can Modulate Interpersonal Comfort Space.

Recent research has investigated whether the representation of space around the body, in terms of reach-action (imagining of reaching another person) and comfort-social (tolerance of the other's proximity) spaces, may reflect a shared sensorimotor basis. Some studies exploiting motor plasticity induced by tool use have not observed sensorimotor identity (i.e., the same mechanisms that underlie, based on sensory information, the representation of proximal space in terms of action possibilities, goal-directed motor actions, and anticipation of the sensorimotor consequences), whereas evidence to the contrary has also emerged. Since the data are not fully convergent, here we wondered whether or not the combination of motor plasticity induced by tool use and the processing of the role of social context might reflect a similar modulation in both spaces. To this end, we conducted a randomized control trial with three groups of participants (N = 62) in which reaching and comfort distances were measured in Pre- and Post-tool-use sessions. The tool-use sessions were conducted under different conditions: (i) in the presence of a social stimulus (determining the social context) (Tool plus Mannequin group); (ii) without any stimulus (Only Tool group); (iii) in the presence of a box (Tool plus Object group) as a control condition. Results showed an extension of comfort distance in the Post-tool session of the Tool plus Mannequin group compared with the other conditions. Conversely, the reaching distance was larger after tool use than at the Pre-tool-use session, independently of the experimental conditions. Our findings suggest that motor plasticity impacts reaching and comfort spaces to different degrees; while reaching space is markedly sensitive to motor plasticity, comfort space needs qualification of social context information.

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.

Representational Processes of Actions Toward and Away from the Body.

The aim of the present study was to investigate the role of mental representation processes during the planning, reaching, and use phases of actions with tools commonly used toward the body (TB, e.g., toothbrush) or away from the body (AB, e.g., pencil). In the first session, healthy participants were asked to perform TB (i.e., making circular movements with the toothbrush near the mouth) and AB (i.e., making circular movements with the pencil near the desk) actions both with (i.e., actual use) and without the tool in hand (i.e., the pantomime of tool use). In the second session, the same participants performed a series of mental rotation tasks involving body- (i.e., face and hands) and object-related (i.e., abstract lines) stimuli. The temporal and kinematic analysis of the motor actions showed that the time required to start the pantomimes (i.e., the planning phase) was shorter for the AB action than for the TB action. In contrast, the reaching phase lasted longer for the AB action than for the TB action. Furthermore, the TB pantomime was associated with the performance in the mental rotation of body-related stimuli, especially during the planning and reaching phases, whereas the AB pantomime was more related to the performance in the mental rotation of object-related stimuli, especially during the tool use phase. Thus, the results revealed that the direction of a goal-directed motor action influences the dynamics of the different phases of the motor action and can determine the type of mental images involved in the planning and execution of the action.

The COVID-19 Stress Perceived on Social Distance and Gender-Based Implications.

The COVID-19 pandemic is an unprecedented event entailing long-term consequences on population health and welfare. Those who contracted the coronavirus may have suffered from both physical and mental health issues that unfold the need for tailored intervention strategies. Hence, our study aims to investigate the psychological and social consequences of COVID-19 on a sample of 86 participants, encompassing 43 patients (clinical group; 25 women; mean age = 50.4 ± 10.1 years) recruited from Bari University Hospital, 19 of whom were hospitalized due to the disease. The remaining 43 were individuals not fallen ill with COVID-19 to date (control group; 25 women; mean age = 50.4 ± 10.1 years). The investigation yielded significant gender differences in post-traumatic stress symptoms, depression, and representation of interpersonal distance (IPD), evaluated through the IES-R, the BDI-II, and the IVAS task, respectively. This pattern of results was not replicated in the control group. In general, participants who reported having experienced the most intense post-traumatic symptoms also presented a greater mood deflection and, more specifically, within the clinical group women obtained the highest scores on both scales. Women reported higher IES-R and BDI-II scores compared to men, that could indicate that women who have contracted COVID-19 are more exposed to post-traumatic and depressive symptoms. Our results also showed a significant effect of COVID-19 on IPD with a tendency of disease-experienced individuals to increase their preferred IPD from adults, children, and elderly people. Regarding gender differences in mood and proxemic behavior, a correlation between depressive symptoms and probable PTSD and a further correlation between probable PTSD and greater IPD were found in women from both clinical and control group. Overall, these findings might contribute to a better understanding of gender-based implications of the current pandemic on mental health, also leading to the development of integrated yet personalized intervention strategies.

Dentin Exposure after Tooth Preparation for Laminate Veneers: A Microscopical Analysis to Evaluate the Influence of Operators' Expertise.

Background: To assess the quantity of dentin exposure detected by 3 operators with different clinical expertise for 2 designs of tooth preparation for laminate veneers: window (WI) and butt joint (BJ). Methods: 20 intact maxillary central incisors were collected and then prepared for laminate veneers to a depth of 0.6 mm, with a cervical mini-chamfer finish line of 0.3 mm. Each prepared tooth was analyzed by 3 operators with different expertise: undergraduate student (ST), general practitioner (GP), and prosthodontist (PR), at sight under magnification. Besides descriptive statistics (CI 95%), 2-way ANOVA and Games−Howell tests were used to analyze differences among groups (α = 0.05). Results: The means of percentage and area of detected dentin exposure were WI = 30.48%, 21.57 mm2; BJ = 30.99%, 21.97 mm2; ST/WI = 22.82%, 16.44 mm2; GP/WI = 58.05%, 40.64 mm2; PR/WI = 10.55%, 7.63 mm2; ST/BJ = 28.99%, 20.83 mm2; GP/BJ = 40.56%, 28.32 mm2; PR/BJ = 23.42%, 16.75 mm2. Significant differences were found between ST/WI vs. GP/WI (p = 0.005) and GP/WI vs. PR/WI (p < 0.001). Conclusions: There was no difference in detection of exposed dentin among operators with different expertise for BJ preparation, whereas differences were found between the general practitioner and the other 2 operators in WI. Moreover, the quantity of exposed dentin was not related to different tooth preparation designs.

Space at home and psychological distress during the Covid-19 lockdown in Italy.

Prolonged periods of restrictions on people's freedom of movement during the first massive wave of the COVID-19 pandemic meant that most people engaged in all their daily activities at home. This suggested the need for the spatial features of the home and its occupants' perception of them to be investigated in terms of people's wellbeing. The present study was conducted on a large sample (N = 1354) drawn from different Italian regions. It examined the relationship between the "objective" and "subjective" dimensions of the home, measured in terms of objective home crowding and satisfaction with the space at home, in relation to perceived stress and the perceived risk of COVID-19 infection during the lockdown. The results showed that perceived stress is influenced by objective home crowding through the mediation of satisfaction with the space at home. These associations were more pronounced in younger generations. The negative association between satisfaction with the space at home and perceived stress was higher, the lower the perceived COVID-19 risk.

How ageing and blindness affect egocentric and allocentric spatial memory.

Egocentric (subject-to-object) and allocentric (object-to-object) spatial reference frames are fundamental for representing the position of objects or places around us. The literature on spatial cognition in blind people has shown that lack of vision may limit the ability to represent spatial information in an allocentric rather than egocentric way. Furthermore, much research with sighted individuals has reported that ageing has a negative impact on spatial memory. However, as far as we know, no study has assessed how ageing may affect the processing of spatial reference frames in individuals with different degrees of visual experience. To fill this gap, here we report data from a cross-sectional study in which a large sample of young and elderly participants (160 participants in total) who were congenitally blind (long-term visual deprivation), adventitiously blind (late onset of blindness), blindfolded sighted (short-term visual deprivation) and sighted (full visual availability) performed a spatial memory task that required egocentric/allocentric distance judgements with regard to memorised stimuli. The results showed that egocentric judgements were better than allocentric ones and above all that the ability to process allocentric information was influenced by both age and visual status. Specifically, the allocentric judgements of congenitally blind elderly participants were worse than those of all other groups. These findings suggest that ageing and congenital blindness can contribute to the worsening of the ability to represent spatial relationships between external, non-body-centred anchor points.

From aMCI to AD: The Role of Visuo-Spatial Memory Span and Executive Functions in Egocentric and Allocentric Spatial Impairments.

A difficulty in encoding spatial information in an egocentric (i.e., body-to-object) and especially allocentric (i.e., object-to-object) manner, and impairments in executive function (EF) are typical in amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD). Since executive functions are involved in spatial encodings, it is important to understand the extent of their reciprocal or selective impairment. To this end, AD patients, aMCI and healthy elderly people had to provide egocentric (What object was closest to you?) and allocentric (What object was closest to object X?) judgments about memorized objects. Participants' frontal functions, attentional resources and visual-spatial memory were assessed with the Frontal Assessment Battery (FAB), the Trail Making Test (TMT) and the Corsi Block Tapping Test (forward/backward). Results showed that ADs performed worse than all others in all tasks but did not differ from aMCIs in allocentric judgments and Corsi forward. Regression analyses showed, although to different degrees in the three groups, a link between attentional resources, visuo-spatial memory and egocentric performance, and between frontal resources and allocentric performance. Therefore, visuo-spatial memory, especially when it involves allocentric frames and requires demanding active processing, should be carefully assessed to reveal early signs of conversion from aMCI to AD.

Period 2: A Regulator of Multiple Tissue-Specific Circadian Functions.

The zebrafish represents a powerful model for exploring how light regulates the circadian clock due to the direct light sensitivity of its peripheral clocks, a property that is retained even in organ cultures as well as zebrafish-derived cell lines. Light-inducible expression of the per2 clock gene has been predicted to play a vital function in relaying light information to the core circadian clock mechanism in many organisms, including zebrafish. To directly test the contribution of per2 to circadian clock function in zebrafish, we have generated a loss-of-function per2 gene mutation. Our results reveal a tissue-specific role for the per2 gene in maintaining rhythmic expression of circadian clock genes, as well as clock-controlled genes, and an impact on the rhythmic behavior of intact zebrafish larvae. Furthermore, we demonstrate that disruption of the per2 gene impacts on the circadian regulation of the cell cycle in vivo. Based on these results, we hypothesize that in addition to serving as a central element of the light input pathway to the circadian clock, per2 acts as circadian regulator of tissue-specific physiological functions in zebrafish.

Optical behaviors, surface treatment, adhesion, and clinical indications of zirconia-reinforced lithium silicate (ZLS): A narrative review.

OBJECTIVES: The present narrative review was focused on the optical properties, surface treatment, adhesion, and clinical indications of zirconia-reinforced lithium silicate ceramics (ZLS) for Computer-aided design / Computer-aided manufacturing (CAD/CAM) technologies. DATA/SOURCES: A literature search was performed by 3 calibrated independent researchers on PubMed, Scopus, Embase, Google Scholar, Dynamed, and Open Grey. The criteria for inclusion were: 1) papers addressing at least one of the following variables about ZLS: optical properties, surface treatment, adhesion, and clinical indications; 2) in vitro, in silico, or in vivo studies; 3) case reports; 4) systematic reviews. The exclusion criteria were: 1) animal studies; 2) non-dental studies; 3) studies only focusing on ZLS used in the heat-pressed process. STUDY SELECTION: 98 records among in vitro studies and case reports were included. CONCLUSIONS: Despite the promising microstructure characteristics of ZLS, increased translucency compared to lithium disilicate ceramics (LS2) was not proven, but acceptable color changes and stability were reported. Mechanical polishing was the most effective method to reduce surface roughness. Moreover, machinability and handling of ZLS resulted harder than LS2. Conventional acid etching procedures seemed effective in conditioning ZLS surface, but no protocol has been established yet. Besides, silane-coupling and dual-curing resin cements were recommended. CLINICAL SIGNIFICANCE: ZLSs can be used for anterior and posterior fixed single-unit CAD/CAM restorations onto both natural teeth and implants, but do not seem to represent a viable treatment option for endocrowns onto posterior teeth or fixed dental prostheses.

Social Distance during the COVID-19 Pandemic Reflects Perceived Rather Than Actual Risk.

Interpersonal space (IPS) is the area surrounding our own bodies in which we interact comfortably with other individuals. During the COVID-19 pandemic, keeping larger IPS than usual, along with wearing a face mask, is one of the most effective measures to slow down the COVID-19 outbreak. Here, we explore the contribution of actual and perceived risk of contagion and anxiety levels in regulating our preferred social distance from other people during the first wave of the COVID-19 pandemic in Italy. In this study, 1293 individuals from six Italian regions with different levels of actual risk of infection participated in an online survey assessing their perceived risk to be infected, level of anxiety and IPS. Two tasks were adopted as measures of interpersonal distance: the Interpersonal Visual Analogue Scale and a questionnaire evaluating interpersonal distance with and without face mask. The results showed that the IPS regulation was affected by how people subjectively perceived COVID-19 risk and the related level of anxiety, not by actual objective risk. This clarifies that the role of threat in prompting avoidant behaviors expressed in increased IPS does not merely reflect environmental events but rather how they are subjectively experienced and represented.

Zirconia-reinforced lithium silicate (ZLS) mechanical and biological properties: A literature review.

OBJECTIVES: This paper aimed to provide a literature review of the mechanical and biological properties of zirconia-reinforced lithium silicate glass-ceramics (ZLS) in Computer-aided design / Computer-aided manufacturing (CAD/CAM) systems. DATA/SOURCES: An extensive search of the literature for papers related to ZLS was made on the databases of PubMed/Medline, Scopus, Embase, Google Scholar, Dynamed, and Open Grey. The papers were selected by 3 independent calibrated reviewers. STUDY SELECTION: The search strategy produced 937 records. After the removal of duplicates and the exclusion of papers that did not meet the inclusion criteria, 71 papers were included. CONCLUSIONS: After reviewing the included records, it was found that two types of ZLS (Vita Suprinity PC; Vita Zahnfabrik and Celtra Duo; Dentsply Sirona) are nowadays available on the market for CAD/CAM systems, similar in their chemical composition, microstructure, and biological-mechanical properties. ZLS is reported to be a biocompatible material, whose fracture resistance can withstand physiological chewing loads. The firing process influences the improvements of strength and fatigue failure load, with a volumetric shrinkage. To date, ZLS can be considered a viable alternative to other glass-ceramics for fixed single restorations. CLINICAL SIGNIFICANCE: . As to biocompatibility and mechanical properties of ZLS, data are still scarce, often controversial and limited to short-term observational periods. These promising ceramics require further in vitro/in vivo studies to accurately define mechanical and biological properties, mainly in the long-term performance of restorations produced with such materials.

The Impact of Lockdown on Couples' Sex Lives.

BACKGROUND: the aim of this study was to perform an Italian telematics survey analysis on the changes in couples' sex lives during the coronavirus disease 2019 (COVID-19) lockdown. METHODS: a multicenter cross sectional study was conducted on people sexually active and in stable relationships for at least 6 months. To evaluate male and female sexual dysfunctions, we used the international index of erectile function (IIEF-15) and the female sexual function index (FSFI), respectively; marital quality and stability were evaluated by the marital adjustment test (items 10-15); to evaluate the severity of anxiety symptoms, we used the Hamilton Anxiety Rating Scale. The effects of the quarantine on couples' relationships was assessed with questions created in-house. RESULTS: we included 2149 participants. The sex lives improved for 49% of participants, particularly those in cohabitation; for 29% it deteriorated, while for 22% of participants it did not change. Women who responded that their sex lives deteriorated had no sexual dysfunction, but they had anxiety, tension, fear, and insomnia. Contrarily, men who reported deteriorating sex lives had erectile dysfunctions and orgasmic disorders. In both genders, being unemployed or smart working, or having sons were risk factors for worsening the couples' sex lives. CONCLUSION: this study should encourage evaluation of the long-term effects of COVID-19 on the sex lives of couples.

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.