Social Modulation of Peripersonal Space Boundaries

Multimodal representation of peripersonal or near space has been demonstrated in the brain of the nonhuman primate through invasive electrophysiological experiments. Representation of peripersonal space in the human brain has been inferred from extinction experiments and functional imaging studies. We present a unique case of lower limb myoclonus in a patient with common variable immunodeficiency which is sensitive to visual stimuli in the peripersonal space and light touch. This case provides further evidence for near space representation in the human brain. We hypothesize that somatopically organized multimodal areas exist in the human brain which code for peripersonal space.

Dedicated neural systems represent the space surrounding the body, termed Peripersonal space (PPS), by integrating visual or auditory stimuli occurring near the body with somatosensory information. As a behavioral proxy to PPS, we measured participants’ reaction time to tactile stimulation while task-irrelevant auditory or visual stimuli were presented at different distances from their body. In 7 experiments we delineated the critical distance at which auditory or visual stimuli boosted tactile processing on the hand, face, and trunk as a proxy of the PPS extension. Three main findings were obtained. First, the size of PPS varied according to the stimulated body part, being progressively bigger for the hand, then face, and largest for the trunk. Second, while approaching stimuli always modulated tactile processing in a space-dependent manner, receding stimuli did so only for the hand. Finally, the extension of PPS around the hand and the face varied according to their relative positioning and stimuli congruency, whereas the trunk PPS was constant. These results suggest that at least three body-part specific PPS representations exist, differing in extension and directional tuning. These distinct PPS representations, however, are not fully independent from each other, but referenced to the common reference frame of the trunk.

In this paper we examine the extent of functional reaching space, or peripersonal space, in immersive three-dimensional virtual reality. In the real world a person’s peripersonal space boundaries can be altered by factors in the environment and by social context. We completed two studies with visual and tactile stimuli to determine peripersonal space boundaries. These studies investigated whether peripersonal space boundaries in an immersive virtual environment are consistent with those in the real world, and could be altered by object and virtual agent interactions. We found that while peripersonal space boundaries were consistent with those in the real world, they were responsive to object and agent interactions. Moreover, while people’s reactions to the objects and agents varied, the peripersonal space boundaries remained consistent. These findings have potential implications for the design of virtual environments.

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.

The effect of limb crossing and limb congruency on multisensory integration in peripersonal space for the upper and lower extremities

Introduction In schizophrenia, there is evidence for anomalies in the extension and plasticity of the peripersonal space (PPS), the portion of space surrounding our body, plastically shaped through motor experiences. An impaired multisensory integration at the PPS level would underpin the disembodiment, a core feature of the disorder linked to subjective perturbations of the sense of self (“Self-disorders”) and of the intersubjective dimension (“schizophrenic autism”). Objectives The present study was aimed at: 1) exploring possible associations between PPS data, psychopathological dimensions, and subjective experiences in schizophrenia; 2) identifying a specific PPS profile in patients with early-onset schizophrenia. Methods A motor training with a tool was used to assess the PPS size and boundaries demarcation in twenty-seven schizophrenia outpatients. Moreover, they underwent a thorough psychopathological evaluation with the Positive And Negative Syndrome Scale (PANSS), the Examination of Anomalous Self Experience scale (EASE) and the Autism Rating Scale (ARS). Subsequently, the sample was divided into early (EOS) and adult-onset (AOS) subgroups, that were compared with respect to their PPS and psychopathological profiles. Results PPS features (size and boundaries demarcation) were associated with PANSS negative score, subjective experiences of existential reorientation (EASE Domain 5 scores) and traits of schizophrenic autism (ARS scores; Fig. 1). PPS parameters (Fig. 2) and ARS scores, but not PANSS and EASE differentiated between early and adult-onset subgroups. Image: Image 2: Conclusions Our results suggest a link between PPS patterns, negative symptoms, and disturbances of the subjective experience, particularly in the intersubjective domain, in schizophrenia. Moreover, they candidate specific PPS profiles and schizophrenic autism traits as EOS markers. Disclosure of Interest None Declared

A plethora of neurocognitive research suggests that the brain segments space into near and far space, known as peripersonal and extrapersonal space. For the purpose of this dissertation, we focus on peripersonal space, which can be categorized as the functional reaching and grasping distance around oneself. There are neurons in the parietal and frontal premotor cortices in the brain that expressly process multisensory stimuli within peripersonal space, and neurophysiological and neuropsychological studies along with fMRI data have produced results that demonstrate this to be biological fact (for a full review, see di Pellegrino [5]). There are some studies have branched out, using immersive virtual environments to determine the modulation of peripersonal space, and in this body of work there is strong evidence that it is modulated by several different social factors [5]. However, to our knowledge, this work has not been extended to encompass a full understanding of the different factors that affect peripersonal space and how it behaves in immersive environments and there is still much to be done in this territory.

Dedicated multisensory mechanisms in the brain represent peripersonal space (PPS), a limited portion of space immediately surrounding the body. Previous studies have illustrated the malleability of PPS representation through hand-object interaction, showing that tool use extends the limits of the hand-centered PPS. In the present study we investigated the effects of a special tool, the wheelchair, in extending the action possibilities of the whole body. We used a behavioral measure to quantify the extension of the PPS around the body before and after Active (Experiment 1) and Passive (Experiment 2) training with a wheelchair and when participants were blindfolded (Experiment 3). Results suggest that a wheelchair-mediated passive exploration of far space extended PPS representation. This effect was specifically related to the possibility of receiving information from the environment through vision, since no extension effect was found when participants were blindfolded. Surprisingly, the active motor training did not induce any modification in PPS representation, probably because the wheelchair maneuver was demanding for non-expert users and thus they may have prioritized processing of information from close to the wheelchair rather than at far spatial locations. Our results suggest that plasticity in PPS representation after tool use seems not to strictly depend on active use of the tool itself, but is triggered by simultaneous processing of information from the body and the space where the body acts in the environment, which is more extended in the case of wheelchair use. These results contribute to our understanding of the mechanisms underlying body–environment interaction for developing and improving applications of assistive technological devices in different clinical populations.

This perspective review focuses on the proposal that predictive multisensory integration occurring in one’s peripersonal space (PPS) supports individuals’ ability to efficiently interact with others, and that integrating sensorimotor signals from the interacting partners leads to the emergence of a shared representation of the PPS. To support this proposal, we first introduce the features of body and PPS representations that are relevant for interpersonal motor interactions. Then, we highlight the role of action planning and execution on the dynamic expansion of the PPS. We continue by presenting evidence of PPS modulations after tool use and review studies suggesting that PPS expansions may be accounted for by Bayesian sensory filtering through predictive coding. In the central section, we describe how this conceptual framework can be used to explain the mechanisms through which the PPS may be modulated by the actions of our interaction partner, in order to facilitate interpersonal coordination. Last, we discuss how this proposal may support recent evidence concerning PPS rigidity in Autism Spectrum Disorder (ASD) and its possible relationship with ASD individuals’ difficulties during interpersonal coordination. Future studies will need to clarify the mechanisms and neural underpinning of these dynamic, interpersonal modulations of the PPS.

Immersive audio technologies require personalized binaural synthesis through headphones to provide perceptually plausible virtual and augmented reality (VR/AR) simulations. We introduce and apply for the first time in VR contexts the quantitative measure called premotor reaction time (pmRT) for characterizing sonic interactions between humans and the technology through motor planning. In the proposed basic virtual acoustic scenario, listeners are asked to react to a virtual sound approaching from different directions and stopping at different distances within their peripersonal space (PPS). PPS is highly sensitive to embodied and environmentally situated interactions, anticipating the motor system activation for a prompt preparation for action. Since immersive VR applications benefit from spatial interactions, modeling the PPS around the listeners is crucial to reveal individual behaviors and performances. Our methodology centered around the pmRT is able to provide a compact description and approximation of the spatiotemporal PPS processing and boundaries around the head by replicating several well-known neurophysiological phenomena related to PPS, such as auditory asymmetry, front/back calibration and confusion, and ellipsoidal action fields.

Immersive virtual reality reveals that visuo-proprioceptive discrepancy enlarges the hand-centred peripersonal space

Time and numerosity estimation in peripersonal and extrapersonal space

A convergent series of studies in monkeys and man suggests that the computation of visual space is performed in several brain regions for different behavioural purposes. Among these multiple spatial areas, the ventral intraparietal cortex, the putamen and the ventral aspect of the premotor cortex (area 6) contain a system for representing visual space near the face (peripersonal space). In these cerebral areas some neurons are bimodal: they have tactile receptive fields on the face, and they can also be driven by visual stimuli located near the tactile field. The spatial correspondence between the visual and tactile receptive fields provides a map of near visual space coded in body-part-centred co-ordinates. In the present study we demonstrate for the first time the existence of a visual peripersonal space centred on the face in humans. In patients with right hemispheric lesions, visual stimuli delivered in the space near the ipsilesional side of the face extinguished tactile stimuli on the contralesional side (cross-modal visuotactile extinction) to the same extent as did an ipsilesional tactile stimulation (unimodal tactile extinction). Furthermore, a visual stimulus presented in the proximity of the contralesional side of the face improved the detection of a left tactile stimulus: i.e. under bilateral tactile presentation patients were more accurate to report the presence of a left tactile stimulus when a simultaneous visual stimulus was presented near the left side of the face. However, when visual stimuli were delivered far from the face, visuotactile extinction and visuotactile facilitation effects were dramatically reduced. These findings are consistent with the hypothesis of a representation of visual peripersonal space coded in bodypart-centred co-ordinates, and they provide a striking demonstration of the modularity of human visual space.

The peripersonal space is an adaptive and flexible interface between the body and the environment that fulfills a dual-motor function: preparing the body for voluntary object-oriented actions to interact with incentive stimuli and preparing the body for defensive responses when facing potentially harmful stimuli. In this position article, we provide arguments for the sensorimotor rooting of the peripersonal space representation and highlight the variables that contribute to its flexible and adaptive characteristics. We also demonstrate that peripersonal space represents a mediation zone between the body and the environment contributing to not only the control of goal-directed actions but also the organization of social life. The whole of the data presented and discussed led us to the proposal of a new theoretical framework linking the peripersonal action space and the interpersonal social space and we highlight how this theoretical framework can account for social behaviors in populations with socio-emotional deficits.

Others' Actions Reduce Crossmodal Integration in Peripersonal Space