The Peripersonal Space: A Space to INTER-ACT Action- and Social-related Modulations of the Space around Us

The zone surrounding our body is of vital importance. In neuroscience this space is captured by the concept of peripersonal space (PPS), a plastic representation integrating tactile and visual stimuli presented on/close to the body. PPS is thought to contribute to the efficient guidance of actions, yet, a clear demonstration of this function is critically lacking. In the first study we provided strong support to this hypothesis by revealing that visual and tactile stimuli interact already during action planning. Such a PPS remapping that precedes motor execution is ideally suited to guiding actions. Recently, it has been suggested a possible PPS involvement in social interactions. In social psychology, interpersonal space (IPS) is the area individuals maintain around themselves into which others cannot intrude without arousing discomfort. Because of some similarities, some authors raised the question of whether PPS and IPS share some functional features. In the second and third study we tested this hypothesis by taking advantage of PPS remapping induced by tool-use. First, we showed that “standard” tool-use ‘extends’ PPS, as measured by reaching-distance toward a peer, but does not affect IPS, as measured by the comfort-distance toward the same peer. Then, we demonstrated that a novel “social” tool-use ‘extends’ PPS and ‘reduces’ IPS. These findings clearly disconfirm the hypothesis of functional overlap between the two spaces. The last study examines the sensitivity of PPS to a fundamental social dimension: ownership. The results indicate that ownership of an object is critical for the PPS remapping to emerge. Visual stimuli strongly affected touch perception during action only when the object belonged to the participant. A similar remapping emerged when simply observing a peer acting on her own object. Taken together, these findings critically inform current models about space perception and about its function in our sensorimotor and social inter-actions

Peripersonal space: its functions, plasticity, and neural basis

Traditional conceptions of peripersonal space emphasised its role in the organisation of skilled action. However, two other aspects of this representation have also been highlighted, namely, its defensive and social aspects. Indeed, having a distinct representation of the space close to the body is crucial for preparing defensive responses to noxious or threatening stimuli. Furthermore, it has been shown that peripersonal space is modulated by social factors. In this chapter, we will discuss these differing conceptions of peripersonal space. Evidence from several lines of research has revealed specialised neural and perceptual mechanisms for representing the space around the body for the defense of the body surface, including ethological and neurophysiological studies in animals, psychophysical studies showing perceptual mechanisms specialised for threatening classes of stimuli, and modulation of perception by specific fears. We will review studies on the motor function of peripersonal space and its role in guiding voluntary object-oriented actions. Recent studies have investigated the neural basis of the social aspect of peripersonal space both in monkey and humans. Finally, we will end by discussing the connection between action-based, defensive and social functions of peripersonal space

The Interpersonal Bodily Self. A link between body and social interactions

Recent research emphasized the importance of one’s own body representation in interpersonal attitudes, revealing the social valence of body representation. The present thesis contribute to the emerging field of research that suggests the existence of a causal link between central body representations and more social and cognitive aspects of the self. The first two studies investigate the cognitive consequences of having an invisible body. The first study showed that the illusion of having an invisible body modulates the interpersonal space, i.e. the distance that people maintain between each other during a social interaction and into which intrusions by others may cause discomfort. The second study shows that the experience of invisibility affects also the perception of gaze direction itself, reducing the range of eyes deviations that participants perceived as directed toward the self. Thus, the experience of invisibility may affect the manner in which we process the attention of others toward the self. The last two studies focus on the difference between interpersonal and peripersonal space, i.e a functional representation of the reaching space. Results from third study showed that a change in body height reveals a dissociation between interpersonal and peripersonal space. The illusion of having a tall body reduced the interpersonal space, but extended the perceived peripersonal space. On the other hand, the illusion of having a short body extended the interpersonal space, leaving the peripersonal space intact. Finally the last study focuses more in depth on the notion of body schema, i.e. a sensorimotor representation of the body used for planning and executing movements. In particular, it was shown that body schema and peripersonal space extent depend on the sense of agency, that is the sense of controlling one’s own motor acts and, through them, the events in the external environmen

An Investigation into Peripersonal Space Representations in Older Adults

Peripersonal space is the space immediately surrounding one\u27s body. This space is believed to have a unique representation in order to facilitate successful interaction with the surrounding environment. Supporting this theory, there are consistent findings of changes in cognition within as compared to beyond peripersonal space, including differences in visual attention and perception. However, research on peripersonal space in healthy populations has largely focused on young adults. Representations of peripersonal space take place in multimodal brain regions, areas that show structural and functional changes during senescence. Because of this, there is reason to suspect that older adults represent peripersonal space differently than young adults and that this will lead to measurable changes on tasks that rely on those representations. The present experiments used a behavioral approach to examine age differences on three distinct, but related phenomena that rely on peripersonal space representations. Experiment 1 assessed the rate and strength of the rubber hand illusion, a multimodal illusion that primarily occurs when a dummy hand is within the peripersonal space representation of a person\u27s real hand. Experiment 2 measured the perceptual consequences of tool use and the ability to flexibly incorporate a tool into one\u27s peripersonal space representation. Experiment 3 looked at the extent to which attention is automatically biased toward the space near an outstretched hand. Finally, the relationship among the tasks was examined to assess the extent to which the three paradigms are measuring the same construct. All three experiments showed significant age-related effects. Young adults consistently exhibited changes in performance when performing the tasks within as compared to beyond peripersonal space. Older adults, however, had the same pattern of performance regardless of whether they performed the task within or beyond peripersonal space. Surprisingly, there were no correlations among the experimental measures, suggesting that the selected tasks may be measuring different aspects of peripersonal space. These results have implications for our understanding of mobility and goal-directed action declines in older adults

The neural response is heightened when watching a person approaching compared to walking away: Evidence for dynamic social neuroscience

The action observation network has been proposed to play a key role in predicting the action intentions (or goals) of others, thereby facilitating social interaction. Key information when interacting with others is whether someone (an agent) is moving towards or away from us, indicating whether we are likely to interact with the person. In addition, to determine the nature of a social interaction, we also need to take into consideration the distance of the agent relative to us as the observer. How this kind of information is processed within the brain is unknown, at least in part because prior studies have not involved live whole-body motion. Consequently, here we recorded mobile EEG in 18 healthy participants, assessing the neural response to the modulation of direction (walking towards or away) and distance (near vs. far distance) during the observation of an agent walking. We evaluated whether cortical alpha and beta oscillations were modulated differently by direction and distance during action observation. We found that alpha was only modulated by distance, with a stronger decrease of power when the agent was further away from the observer, regardless of direction. Critically, by contrast, beta was found to be modulated by both distance and direction, with a stronger decrease of power when the agent was near and facing the participant (walking towards) compared to when they were near but viewed from the back (walking away). Analysis revealed differences in both the timing and distribution of alpha and beta oscillations. We argue that these data suggest a full understanding of action observation requires a new dynamic neuroscience, investigating actual interactions between real people, in real world environments

The spatial logic of fear

Peripersonal space (PPS) is the multimodal sensorimotor representation of the space surrounding the body. This thesis investigates how PPS is modulated by emotional faces, which represent particularly salient cue in our environment. Study 1 shows that looming neutral, joyful, and angry faces gradually facilitate motor responses to tactile stimuli. Conversely, looming fearful faces show no such effect. Also, at the closest position in PPS, multisensory response facilitation is lower for fearful than neutral faces. Study 2a addresses the hypothesis that fearful faces promote a redirection of attention towards the peripheral space. In line with this, it shows that motor responses to tactile stimuli are facilitated when a looming fearful face is associated with the appearance of a visual element presented in the periphery, rather than close to the face. Also, this effect is found in near space and not in far space. This result suggests that a near looming fearful face elicits a redirection of attention to the peripheral space. Such effect is not found for neutral, joyful, or angry faces (Study 2b). Study 3 shows that the redirection of attention in PPS by fearful faces is accompanied by a modulation of the electrophysiological signal associated with face processing (N170). Finally, Study 4 shows that the skin conductance response to looming fearful, but not joyful or neutral faces, is modulated by the distance of the face from participants’ body, being maximal in the near space. Together these studies show that, at variance with other emotions, fearful faces shift attention to other portions of space - than that of the face - where the threat may be located. It is argued that this fear-evoked redirection of attention may enhance the defensive function of PPS, when most needed, i.e., when the source of threat is nearby, but its location remains unknown

Frontier of Self and Impact Prediction

The construction of a coherent representation of our body and the mapping of the space immediately surrounding it are of the highest ecological importance. This space has at least three specificities: it is a space where actions are planned in order to interact with our environment; it is a space that contributes to the experience of self and self-boundaries, through tactile processing and multisensory interactions; last, it is a space that contributes to the experience of body integrity against external events. In the last decades, numerous studies have been interested in peripersonal space (PPS), defined as the space directly surrounding us and which we can interact with (for reviews, see Cléry et al., 2015b; de Vignemont and Iannetti, 2015; di Pellegrino and Làdavas, 2015). These studies have contributed to the understanding of how this space is constructed, encoded and modulated. The majority of these studies focused on subparts of PPS (the hand, the face or the trunk) and very few of them investigated the interaction between PPS subparts. In the present review, we summarize the latest advances in this research and we discuss the new perspectives that are set forth for futures investigations on this topic. We describe the most recent methods used to estimate PPS boundaries by the means of dynamic stimuli. We then highlight how impact prediction and approaching stimuli modulate this space by social, emotional and action-related components involving principally a parieto-frontal network. In a next step, we review evidence that there is not a unique representation of PPS but at least three sub-sections (hand, face and trunk PPS). Last, we discuss how these subspaces interact, and we question whether and how bodily self-consciousness (BSC) is functionally and behaviorally linked to PPS

Parietal maps of visual signals for bodily action planning

The posterior parietal cortex (PPC) has long been understood as a high-level integrative station for computing motor commands for the body based on sensory (i.e., mostly tactile and visual) input from the outside world. In the last decade, accumulating evidence has shown that the parietal areas not only extract the pragmatic features of manipulable objects, but also subserve sensorimotor processing of others’ actions. A paradigmatic case is that of the anterior intraparietal area (AIP), which encodes the identity of observed manipulative actions that afford potential motor actions the observer could perform in response to them. On these bases, we propose an AIP manipulative action-based template of the general planning functions of the PPC and review existing evidence supporting the extension of this model to other PPC regions and to a wider set of actions: defensive and locomotor actions. In our model, a hallmark of PPC functioning is the processing of information about the physical and social world to encode potential bodily actions appropriate for the current context. We further extend the model to actions performed with man-made objects (e.g., tools) and artifacts, because they become integral parts of the subject’s body schema and motor repertoire. Finally, we conclude that existing evidence supports a generally conserved neural circuitry that transforms integrated sensory signals into the variety of bodily actions that primates are capable of preparing and performing to interact with their physical and social world

Investigating Neural Sensorimotor Mechanisms Underlying Flight Expertise in Pilots: Preliminary Data From an EEG Study

Over the last decade, the efforts toward unraveling the complex interplay between the brain, body, and environment have set a promising line of research that utilizes neuroscience to study human performance in natural work contexts such as aviation. Thus, a relatively new discipline called neuroergonomics is holding the promise of studying the neural mechanisms underlying human performance in pursuit of both theoretical and practical insights. In this work, we utilized a neuroergonomic approach by combining insights from ecological psychology and embodied cognition to study flight expertise. Specifically, we focused on the Mirror Neuron system as a key correlate for understanding the interaction between an individual and the environment, suggesting that it can be used to index changes in the coupling of perception-action associated with skill development. In this study, we measured the EEG mu suppression as a proxy of the Mirror Neuron system in experts (pilots) and novices while performing a distance estimation task in a landing scenario. To survey the specificity of this measure, we considered central, parietal and occipital electrode pools and analyzed alpha (8–13 Hz) and beta (18–25 Hz) rhythm bands. We hypothesized that in experts vs. novices, specific neural sensorimotor brain activity would underpin the connection between perception and action in an in-flight context. Preliminary results indicate that alpha and beta rhythm suppression was area-specific irrespective of groups, present in the central electrodes placed over the motor areas. Group analysis revealed that specifically alpha mu rhythm, but not beta, was significantly more suppressed in pilots vs. novices. Complementing these findings we found a trend in which the strength of mu suppression increased with the sense of presence experienced by the pilots. Such sensorimotor activation is in line with the idea that for a pilot, a distance judgment is intimately associated with the function of landing. This reflects the ability to use optical invariants to see the world in terms of the capabilities of the aircraft (e.g., reachability and glide angle). These preliminary findings support the role of embodied simulation mechanisms in visual perception and add important insights into a practical understanding of flight expertise, suggesting sensorimotor mechanisms as potential neuro-markers