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

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

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

Behavioral, Neural, and Computational Principles of Bodily Self-Consciousness

Recent work in human cognitive neuroscience has linked self-consciousness to the processing of multisensory bodily signals (bodily self-consciousness [BSC]) in fronto-parietal cortex and more posterior temporo-parietal regions. We highlight the behavioral, neurophysiological, neuroimaging, and computational laws that subtend BSC in humans and non-human primates. We propose that BSC includes body-centered perception (hand, face, and trunk), based on the integration of proprioceptive, vestibular, and visual bodily inputs, and involves spatio-temporal mechanisms integrating multisensory bodily stimuli within peripersonal space (PPS). We develop four major constraints of BSC (proprioception, body-related visual information, PPS, and embodiment) and argue that the fronto-parietal and temporo-parietal processing of trunk-centered multisensory signals in PPS is of particular relevance for theoretical models and simulations of BSC and eventually of self-consciousness

Fronto-parietal brain responses to visuotactile congruence in an anatomical reference frame

Spatially and temporally congruent visuotactile stimulation of a fake hand together with one’s real hand may result in an illusory self-attribution of the fake hand. Although this illusion relies on a representation of the two touched body parts in external space, there is tentative evidence that, for the illusion to occur, the seen and felt touches also need to be congruent in an anatomical reference frame. We used functional magnetic resonance imaging and a somatotopical, virtual reality-based setup to isolate the neuronal basis of such a comparison. Participants’ index or little finger was synchronously touched with the index or little finger of a virtual hand, under congruent or incongruent orientations of the real and virtual hands. The left ventral premotor cortex responded significantly more strongly to visuotactile co- stimulation of the same versus different fingers of the virtual and real hand. Conversely, the left anterior intraparietal sulcus responded significantly more strongly to co-stimulation of different versus same fingers. Both responses were independent of hand orientation congruence and of spatial congruence of the visuotactile stimuli. Our results suggest that fronto- parietal areas previously associated with multisensory processing within peripersonal space and with tactile remapping evaluate the congruence of visuotactile stimulation on the body according to an anatomical reference frame

Ready Both to Your and to My Hands: Mapping the Action Space of Others

To date, mutual interaction between action and perception has been investigated mainly by focusing on single individuals. However, we perceive affording objects and acts upon them in a surrounding world inhabited by other perceiving and acting bodies. Thus, the issue arises as to whether our action-oriented object perception might be modulated by the presence of another potential actor. To tackle this issue we used the spatial alignment effect paradigm and systematically examined this effect when a visually presented handled object was located close either to the perceiver or to another individual (a virtual avatar). We found that the spatial alignment effect occurred whenever the object was presented within the reaching space of a potential actor, regardless of whether it was the participant's own or the other's reaching space. These findings show that objects may afford a suitable motor act when they are ready not only to our own hand but also, and most importantly, to the other's hand. Our proposal is that this effect is likely to be due to a mapping of our own and the other's reaching space and we posit that such mapping could play a critical role in joining our own and the other's action

Testosterone administration increases the size of womens' peripersonal space: An embodied index of social dominance

Peripersonal space (PPS) is the space immediately surrounding the body, encoded by a specific frontoparietal network of multimodal neurons. Stimuli in PPS are represented in a body-part centred manner in terms of possibilities for action, and PPS representations function to facilitate defensive and/or approaching responses to stimuli. The size of PPS differs between individuals and contexts, with physical and psychological factors having a determining role on the size of PPS. For these reasons, PPS has been conceptualised as ‘the space of the bodily self'. In this study we investigated whether the dominance enhancing effects of testosterone may reflect in changes of the representation of PPS. We conducted a double-blind placebo-controlled within-subjects testosterone administration study in women (N=19) where participants performed a multisensory-integration task (a commonly used measure of PPS) while facing an unknown confederate. Results indicated that in comparison to placebo, the administration of testosterone caused a significant enlargement of participants' PPS, suggesting that testosterone caused participants to reflexively appropriate a larger space as their own. This effect was particularly pronounced in participants with higher trait anxiety, converging with other research which has shown that the dominance enhancing effects of testosterone administration can be particularly effective in anxious individuals. Results also indicated a multisensory-facilitation effect around the confederate, which was constant across testosterone and placebo conditions – confirming that the effect of testosterone was self-specific. The PPS boundary gradient was unchanged by testosterone. These findings suggest that an enlarged PPS may provide an embodied index of social dominance. Further, because PPS representations function to support approaching and/or defensive responses to the environment, an enlarged PPS due to raised testosterone may support the enhanced approach behaviour and vigilance to threat known to be conferred by testosterone

Your place or mine:Shared sensory experiences elicit a remapping of peripersonal space

Our perceptual systems integrate multisensory information about objects that are close to our bodies, which allow us to respond quickly and appropriately to potential threats, as well as act upon and manipulate useful tools. Intriguingly, the representation of this area close to our body, known as the multisensory 'peripersonal space' (PPS), can expand or contract during social interactions. However, it is not yet known how different social interactions can alter the representation of PPS. In particular, shared sensory experiences, such as those elicited by bodily illusions such as the enfacement illusion, can induce feelings of ownership over the other's body which has also been shown to increase the remapping of the other's sensory experiences onto our own bodies. The current study investigated whether such shared sensory experiences between two people induced by the enfacement illusion could alter the way PPS was represented, and whether this alteration could be best described as an expansion of one's own PPS towards the other or a remapping of the other's PPS onto one's own. An audio-tactile integration task allowed us to measure the extent of the PPS before and after a shared sensory experience with a confederate. Our results showed a clear increase in audio-tactile integration in the space close to the confederate's body after the shared experience. Importantly, this increase did not extend across the space between participant and confederate, as would be expected if the participant's PPS had expanded. Thus, the pattern of results is more consistent with a partial remapping of the confederate's PPS onto the participant's own PPS. These results have important consequences for our understanding of interpersonal space during different kinds of social interactions. (C) 2014 Elsevier Ltd. All rights reserved

Interpersonal representations of touch in somatosensory cortex are modulated by perspective

Observing others being touched activates similar brain areas as those activated when one experiences a touch oneself. Event-related potential (ERP) studies have revealed that modulation of somatosensory components by observed touch occurs within 100 ms after stimulus onset, and such vicarious effects have been taken as evidence for empathy for others' tactile experiences. In previous studies body parts have been presented from a first person perspective. This raises the question of the extent to which somatosensory activation by observed touch to body parts depends on the perspective from which the body part is observed. In this study (N = 18), we examined the modulation of somatosensory ERPs by observed touch delivered to another person's hand when viewed as if from a first person versus a third person perspective. We found that vicarious touch effects primarily consist of two separable components in the early stages of somatosensory processing: an anatomical mapping for touch in first person perspective at P45, and a specular (mirror like) mapping for touch in third person perspective at P100. This is consistent with suggestions that vicarious representations exist to support predictions for one's own bodily events, but also to enable predictions of a social or interpersonal kind, at distinct temporal stages

Embodied Simulation and Touch: the Sense of Touch in Social Cognition

This paper explores the sense of touch in relation to social cognition offering a new take on multisensory integration in the brain, within the framework of Embodied simulation (ES) theory. ES provides a new empirically based notion of intersubjectivity, viewed first and foremost as intercorporeality. In relation to touch, by means of ES we do not just “see” a sensation experienced by someone else and then understand it through an inference by analogy. By means of ES we can map others’ sensations by re-using our own motor, somatosensory and viscero-motor representations. ES provides an original and unitary account of basic aspects of intersubjectivity, demonstrating how deeply our making sense of others’ living and acting bodies is rooted in the power of re-using our own motor, somatosensory and viscero-motor resources