•We interact with the environment occur in the space close to the body, named peripersonal space (PPS).•PPS is represented by a dedicated parieto-frontal, multisensory-motor system.•PPS shapes ...depending on body-objects interactions (tool-use, training, immobilization).•But also abstract interactions between the individual and the environment, including the others.•PPS underlies a self-other distinction, involved in self-consciousness.
Our brain has developed a specific system to represent the space closely surrounding the body, termed peripersonal space (PPS). This space has a key functional role as it is where all physical interactions with objects in the environment occur. Here I describe how multisensory neurons in a specific fronto-parietal network map the PPS by integrating tactile stimuli on the body with visual or auditory information related to external objects specifically when they are close to the body. I show how PPS representation is not only multisensory, but actually multisensory-motor, as the PPS system interacts with motor areas to trigger appropriate responses. The extent of PPS is not fixed, but it is shaped by experience, as PPS may encompass farther portions of space, once the individual has interacted with them, (e.g., with tools), or it contracts, if interactions are limited because of external constraints, body, or brain injury. Interactions between the individual and the environment are not only physical but may also be “abstract”. Recent data show that PPS adapts as a consequence of technology-mediated or social interactions. Finally, I propose that besides low-level sensory-motor representations of the space around the different parts of the body, mediating body-objects interactions, the multisensory PPS system also underlies a general representation of the self as distinct from the environment and the others. PPS thus supports self-location, contributes to bodily self-consciousness and mediates higher-level cognitive functions.
We take the feeling that our body belongs to us for granted. However, recent research has shown that it is possible to alter the subjective sensation of body ownership (BO) by manipulating ...multisensory bodily inputs. Several frontal and parietal regions are known to specifically process multisensory cues presented close to the body, i.e., within the peripersonal space (PPS). It has been proposed that these PPS fronto-parietal regions also underlie BO. However, most previous studies investigated the brain mechanisms of either BO or of PPS processing separately and by using a variety of paradigms. Here, we conducted an extensive meta-analysis of functional neuroimaging studies to investigate PPS and BO processing in humans in order to: a) assess quantitatively where each one of these functions was individually processed in the brain; b) identify whether and where these processes shared common or engaged distinct brain mechanisms; c) characterize these areas in terms of whole-brain co-activation networks and functions, respectively. We identified (i) a bilateral PPS network including superior parietal, temporo-parietal and ventral premotor regions and (ii) a BO network including posterior parietal cortex (right intraparietal sulcus, IPS; and left IPS and superior parietal lobule, SPL), right ventral premotor cortex, and the left anterior insula. Co-activation maps related to both PPS and BO encompassed largely overlapping fronto-parietal networks, but whereas the PPS network was more frequently associated with sensorimotor tasks, the BO network was rather associated with attention and awareness tasks. Finally, the conjunction analysis showed that (iii) PPS and BO tasks anatomically overlapped only in two clusters located in the left parietal cortex (dorsally at the intersection between the SPL, the IPS and area 2 and ventrally between areas 2 and IPS). Distinct activations were located for PPS at the temporo-parietal junction and for BO in the anterior insula. These results in PPS and BO and provide evidence-based insight about the overlap of the two processes in the IPS region and the extensive connectivity between the two associated co-activation networks. They also show significant dissociations, with PPS fronto-parietal areas located more proximal to the central sulcus than BO areas. Such anatomical distinction may also reflect the different functions of the two processes, whereby PPS areas underlie a multisensory-motor interface for body-objects interaction and BO areas being involved in bodily awareness and self-consciousness.
•A meta-analysis of peripersonal space (PPS) and body ownership (BO) tasks is done.•Both engaged fronto-parietal regions with an overlap in the left parietal cortex.•PPS in addition activated temporo-parietal and BO the left anterior insular regions.•PPS was associated with motor execution and BO with cognitive behavioral domains.•Both domains possessed largely overlapping whole-brain co-activation networks.
We physically interact with external stimuli when they occur within a limited space immediately surrounding the body, i.e., Peripersonal Space (PPS). In the primate brain, specific fronto-parietal ...areas are responsible for the multisensory representation of PPS, by integrating tactile, visual and auditory information occurring on and near the body. Dynamic stimuli are particularly relevant for PPS representation, as they might refer to potential harms approaching the body. However, behavioural tasks for studying PPS representation with moving stimuli are lacking. Here we propose a new dynamic audio-tactile interaction task in order to assess the extension of PPS in a more functionally and ecologically valid condition.
Participants vocally responded to a tactile stimulus administered at the hand at different delays from the onset of task-irrelevant dynamic sounds which gave the impression of a sound source either approaching or receding from the subject's hand. Results showed that a moving auditory stimulus speeded up the processing of a tactile stimulus at the hand as long as it was perceived at a limited distance from the hand, that is within the boundaries of PPS representation. The audio-tactile interaction effect was stronger when sounds were approaching compared to when sounds were receding.
This study provides a new method to dynamically assess pps representation: The function describing the relationship between tactile processing and the position of sounds in space can be used to estimate the location of PPS boundaries, along a spatial continuum between far and near space, in a valuable and ecologically significant way.
Integrating information across sensory systems is a critical step toward building a cohesive representation of the environment and one's body, and as illustrated by numerous illusions, scaffolds ...subjective experience of the world and self. In the last years, classic principles of multisensory integration elucidated in the subcortex have been translated into the language of statistical inference understood by the neocortical mantle. Most importantly, a mechanistic systems‐level description of multisensory computations via probabilistic population coding and divisive normalization is actively being put forward. In parallel, by describing and understanding bodily illusions, researchers have suggested multisensory integration of bodily inputs within the peripersonal space as a key mechanism in bodily self‐consciousness. Importantly, certain aspects of bodily self‐consciousness, although still very much a minority, have been recently casted under the light of modern computational understandings of multisensory integration. In doing so, we argue, the field of bodily self‐consciousness may borrow mechanistic descriptions regarding the neural implementation of inference computations outlined by the multisensory field. This computational approach, leveraged on the understanding of multisensory processes generally, promises to advance scientific comprehension regarding one of the most mysterious questions puzzling humankind, that is, how our brain creates the experience of a self in interaction with the environment.
Integrating information across sensory systems is a critical step toward building a cohesive representation of the environment and one's body, and as illustrated by numerous illusions, scaffolds subjective experience of the world and self. In the last years, classic principles of multisensory integration elucidated in the subcortex have been translated into the language of statistical inference understood by the neocortical mantle. In this review, we first highlight the classical principles of multisensory integration as the starting point for both the study of multisensory integration and its sibling field of bodily self‐consciousness. Then, we respectively detail the major advances within each field in the last decade.
The space around the body, i.e., peripersonal space (PPS), is conceived as a multisensory-motor interface between body and environment. PPS is represented by frontoparietal neurons integrating ...tactile, visual, and auditory stimuli occurring near the body 1–7. PPS is plastic, because it extends by using a tool to reach far objects 8–10. Although interactions with others occur within PPS, little is known about how social environment modulates it. Here, we show that presence and interaction with others shape PPS representation. Participants performed a tactile detection task on their face while concurrent task-irrelevant sounds approached toward or receded from their face. Because a sound affects touch when occurring within PPS 6, 10–12, we calculated the critical distance where sounds speeded up tactile reaction time as a proxy of PPS boundaries. Experiment 1 shows that PPS boundaries shrink when subjects face another individual, as compared to a mannequin, placed in far space. Experiment 2 and 3 show that, after playing an economic game with another person, PPS boundaries between self and other merge, but only if the other behaved cooperatively. These results reveal that PPS representation is sensitive to social modulation, showing a link between low-level sensorimotor processing and high-level social cognition.
► PPS is a multisensory-motor interface between body and environment ► Little is known about how social environment affects PPS representation ► PPS boundaries vary depending on presence of and interaction with others ► Low-level sensory-motor processes and high-level social cognition mutually interact
In this paper, we advocate the combination of four key ingredients that we believe are necessary to design long-lasting effective treatments for neurorehabilitation: (i) motor-cognitive training, ...(ii) evidence-based neuroscience principles, in particular those related to body perception, (iii) motivational games, and (iv) empowerment techniques. Then, we propose virtual reality (VR) as the appropriate medium to encompass all the requirements mentioned above. VR is arguably one of the most suitable technologies for neurorehabilitation able to integrate evidence-based neurorehabilitation techniques and neuroscience principles into motivating training approaches that promote self-management by empowering patients to own their recovery process. We discuss the advantages and challenges of such an approach on several exemplary applications and outline directions for future developments. We strongly believe that the combination of positive psychology and positive technology mediated by VR-based interventions can heavily impact the rehabilitation outcomes of motor-cognitive functions along all the stages of the rehabilitation path.
Despite technical advances in brain machine interfaces (BMI), for as-yet unknown reasons the ability to control a BMI remains limited to a subset of users. We investigate whether individual ...differences in BMI control based on motor imagery (MI) are related to differences in MI ability. We assessed whether differences in kinesthetic and visual MI, in the behavioral accuracy of MI, and in electroencephalographic variables, were able to differentiate between high- versus low-aptitude BMI users. High-aptitude BMI users showed higher MI accuracy as captured by subjective and behavioral measurements, pointing to a prominent role of kinesthetic rather than visual imagery. Additionally, for the first time, we applied mental chronometry, a measure quantifying the degree to which imagined and executed movements share a similar temporal profile. We also identified enhanced lateralized μ-band oscillations over sensorimotor cortices during MI in high- versus low-aptitude BMI users. These findings reveal that subjective, behavioral, and EEG measurements of MI are intimately linked to BMI control. We propose that poor BMI control cannot be ascribed only to intrinsic limitations of EEG recordings and that specific questionnaires and mental chronometry can be used as predictors of BMI performance (without the need to record EEG activity).
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.
A network of brain regions including the ventral premotor cortex (vPMc) and the posterior parietal cortex (PPc) is consistently recruited during processing of multisensory stimuli within peripersonal ...space (PPS). However, to date, information on the causal role of these fronto-parietal areas in multisensory PPS representation is lacking. Using low-frequency repetitive TMS (rTMS; 1 Hz), we induced transient virtual lesions to the left vPMc, PPc, and visual cortex (V1, control site) and tested whether rTMS affected audio–tactile interaction in the PPS around the hand. Subjects performed a timed response task to a tactile stimulus on their right (contralateral to rTMS) hand while concurrent task-irrelevant sounds were presented either close to the hand or 1 m far from the hand. When no rTMS was delivered, a sound close to the hand reduced RT-to-tactile targets as compared with when a far sound was presented. This space-dependent, auditory modulation of tactile perception was specific to a hand-centered reference frame. Such a specific form of multisensory interaction near the hand can be taken as a behavioral hallmark of PPS representation. Crucially, virtual lesions to vPMc and PPc, but not to V1, eliminated the speeding effect due to near sounds, showing a disruption of audio–tactile interactions around the hand. These findings indicate that multisensory interaction around the hand depends on the functions of vPMc and PPc, thus pointing to the necessity of this human fronto-parietal network in multisensory representation of PPS.
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.
•Peripersonal space representation was assessed using an audiotactile integration task.•Shared sensory stimulation between self and other changes processing of other׳s body.•We investigated whether it could also induce changes in processing of other׳s PPS.•Shared sensory stimulation increased audiotactile integration near the other׳s body.•The other׳s PPS was partly “remapped”; events near their body became more salient.
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