More than skin deep: body representation beyond primary somatosensory cortex

The neural circuits underlying initial sensory processing of somatic information are relatively well understood. In contrast, the processes that go beyond primary somatosensation to create more abstract representations related to the body are less clear. In this review, we focus on two classes of higher-order processing beyond somatosensation. Somatoperception refers to the process of perceiving the body itself, and particularly of ensuring somatic perceptual constancy. We review three key elements of somatoperception: (a) remapping information from the body surface into an egocentric reference frame (b) exteroceptive perception of objects in the external world through their contact with the body and (c) interoceptive percepts about the nature and state of the body itself. Somatorepresentation, in contrast, refers to the essentially cognitive process of constructing semantic knowledge and attitudes about the body, including: (d) lexical-semantic knowledge about bodies generally and one’s own body specifically, (e) configural knowledge about the structure of bodies, (f) emotions and attitudes directed towards one’s own body, and (g) the link between physical body and psychological self. We review a wide range of neuropsychological, neuroimaging and neurophysiological data to explore the dissociation between these different aspects of higher somatosensory function

Ghost buster: The reality of one's own body

What are the epistemic bases of the knowledge of the reality of our own body? Proprioception plays a primordial role in body representation and more particularly at the level of body schema. Without proprioception people can feel amputated and the mislocalization of proprioceptive information through the remapping of the Penfield Homonculus induces illusions of phantom limbs, illusions that contradictory visual feedback cannot erase. However, it turns out that it is not as simple as that and that vision also intervenes in body knowledge: vision of one's own body allows deafferented patients to move and phantom limbs to disappear. Finally, the existence of phantom limbs in aplasic patients as well as studies on neonates provide evidence of an innate component of body representation

Widening the body to rubber hands and tools: what's the difference?

The brain represents the body in different ways (e.g., perceptual, motor) for different purposes (recognising oneself, acting in space). Several concepts and even more numerous labels (e.g., body image, body schema) have historically been proposed to define these representations in operational terms. Recent evidence of embodiment of external objects has added complexity to an already quite intricate picture. In particular, because of their perceptual and motor effects, both rubber hands and tools can be conceived as embodied, that is, represented in the brain as if they were parts of one's own body. But are there any limits to what we can embody? What constraints lay upon embodiment? And are they similar both for motor embodiment (i.e. integration within the body schema) and for perceptual embodiment (i.e. integration within the body image)? Here, we consider the implications emerging from the different, and up-to-now relatively separate research domains of tool use and rubber hand illusion for understanding the rules of embodiment. In particular, we compare what the embodiment of tools and prostheses may or may not have in common. We conclude that in both cases, although for different reasons and with different constraints, embodiment is only partial

The neuroscience of body memory: From the self through the space to the others.

Abstract Our experience of the body is not direct; rather, it is mediated by perceptual information, influenced by internal information, and recalibrated through stored implicit and explicit body representation (body memory). This paper presents an overview of the current investigations related to body memory by bringing together recent studies from neuropsychology, neuroscience, and evolutionary and cognitive psychology. To do so, in the paper, I explore the origin of representations of human body to elucidate their developmental process and, in particular, their relationship with more explicit concepts of self. First, it is suggested that our bodily experience is constructed from early development through the continuous integration of sensory and cultural data from six different representations of the body, i.e., the Sentient Body (Minimal Selfhood), the Spatial Body (Self Location), the Active Body (Agency), the Personal Body (Whole Body Ownership – Me); the Objectified Body (Objectified Self – Mine), and the Social Body (Body Satisfaction – Ideal Me). Then, it is suggested that these six representations can be combined in a coherent supramodal representation, i.e. the "body matrix", through a predictive, multisensory processing activated by central, top–down, attentional processes. From an evolutionary perspective, the main goal of the body matrix is to allow the self to protect and extend its boundaries at both the homeostatic and psychological levels. From one perspective, the self extends its boundaries (peripersonal space) through the enactment and recognition of motor schemas. From another perspective, the body matrix, by defining the boundaries of the body, also defines where the self is present, i.e., in the body that is processed by the body matrix as the most likely to be its one, and in the space surrounding it. In the paper I also introduce and discuss the concept of "embodied medicine": the use of advanced technology for altering the body matrix with the goal of improving our health and well-being

Space in action: motor aspects of peripersonal space representation

Spazio in azione: aspetti motori della rappresentazione dello spazio peripersonal

How do healthy individuals adapt to reversed vision generated when using mirror specs? An investigation into mirror devices, adaptation to body schema and imagery ability in healthy participants

Introduction: This study investigates a new form of Mirror Therapy (MT), the Mirror Specs. Evidence suggests that MT is a non-invasive, cost effective method of reducing pain and increasing functioning in some chronic pain conditions. There is no clear explanation for the underlying mechanisms of MT, however, a plausible hypothesis suggests that adaptation to the Body Schema is an integral component. Aims and Hypotheses: The current study examined Body Schema adaptation in healthy participants when performing a Finger Tapping Task with both Mirror Specs and a Mirror Box. It was hypothesised that adaptation would be indicated by increases in Reaction Times (RTs) and Error Rates when comparing unimanual phases of a Finger Tapping Task, following a bimanual „adaptation‟ phase. It was hypothesised that there would be no difference between participants‟ ability to adapt to each device. Finally, the study proposed that there would be a relationship between the adaptation observed on the Finger Tapping Task and participants individual imagery abilities. Method: Participants performed 4 phases of a Finger Tapping Task with alternate bimanual and unimanual phases when using both the Mirror Specs and Mirror Box. Imagery abilities were measured using self-report questionnaires and a Motor Imagery computer task. Results and Discussion: Repeated Measures ANOVAs revealed reductions in RTs and Error Rates in Phase 3 compared to Phase 1 on the Finger Tapping Task. There were no differences between RTs and Error Rates when using the Mirror Specs and Mirror Box. These findings suggest that healthy participants were able to use each Mirror Device effectively and this provide impetus for the proposal that Mirror Specs could provide a practical, cost effective addition to rehabilitation services. Finally, there were no clinically significant relationships between use of the Mirror Devices and imagery abilities, thereby indicating imagery abilities did not influence how participants adapted to using the Mirror Devices

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

In the Beginning was the Deed: From Sensorimotor Interactions to Integrative Spatial Encodings

Goal-oriented behavior requires reliable predictions regarding action outcomes. The theory of event segmentation and the free energy principle allow to derive hypotheses regarding the formation and maintenance of predictive models and their representational format. According to the free energy principle, cognitive systems constantly try to infer the causes of perceived sensations. This results in the formation of predictive models based on sensorimotor experience. Even if there is an ongoing debate regarding the representational format of these models, an integrative spatial code, which integrates different modalities in an abstract representation seems plausible. The integration process is assumed to be biased towards behaviorally relevant modalities. Moreover, a striving for consistency is assumed to maintain unambiguous states. Besides the representational format, the prediction process itself is of central interest. According to the event segmentation theory, cognitive systems segment the stream of sensorimotor information along significant changes, so-called event boundaries. Hence, it seems likely that predictions are carried out in terms of a simulation of the next, desired event boundary within the proposed integrative spatial code. The spatial code might support mental simulation in general, providing sensorimotor grounding to higher cognitive functions – as proposed by theories of embodied cognition. The proposed properties of the integrative spatial code were investigated in four studies, concerning the questions (i) whether multisensory integration is biased towards action-relevant modalities, (ii) how representations are kept consistent across frames of reference in case of multisensory conflict, (iii) if predictive models provide an anticipatory, event-like structure in the service of behavior control, and (iv) how different modalities are combined through a spatial code in the service of predictive simulations. The obtained results confirm the assumptions regarding the proposed integrative spatial code. The combination of the free energy principle and the theory of event segmentation seems a viable approach to account for the emergence of a predictive, integrative spatial code from sensorimotor interactions. The results allow the derivation of design principles for an artificial spatial reasoning system and the developed experimental paradigms allow further investigations of the causal role of spatial models in higher cognitive functions

Disturbances of multisensory processing in schizophrenia spectrum disorders: a behavioural and neurophysiological account

Self-disorders have long been considered as a central nucleus of the schizophrenic experience. It has been suggested that such self-disturbances might be associated with abnormal multisensory integration and abnormal bodily self-awareness. The primary goal of this thesis was to explore the behavioural and neurophysiological markers of self-disturbances in schizophrenia and in high schizotypy (i.e. a sub-clinical trait linked to schizophrenia). Specifically, we aimed at (i) investigating the temporal acuity in individuals with low and high schizotypy (ii) measuring aspects of the neural responses to multisensory integration in low and high schizotypes (iii) exploring how body representation abnormalities in both schizophrenic patients and high schizotypes affect basic processes of self-perception. In line with previous research showing a reduced multisensory acuity in schizophrenia, results from Chapter Three revealed a significant relationship between the temporal window within which two stimuli are integrated (i.e. TWI), and schizotypal personality traits; namely, higher schizotypal traits are associated with wider TWIs. In Chapter Four, we provided evidence of a selective relationship between the TWI for visuo-tactile stimuli and the individual beta frequency (IBF), i.e, slower IBFs accounts for larger TWIs, and between the TWI and schizotypy, i.e. wider TWIs are linked to higher schizotypal traits. In Chapter Five, we have demonstrated that patients with schizophrenia possess more malleable body representations and that these abnormalities are linked to early markers of vulnerability to the disorder (i.e. basic symptoms). Finally, findings from Chapter Six revealed that the abnormalities in bodily self-awareness observed in schizophrenia might extend to schizotypy, suggesting that such abnormalities could represent a trait marker for schizophrenia proneness. All in all, our results suggest that the abnormalities in multisensory integration and bodily awareness observed in schizophrenia spectrum disorders might produce a distortion in the structure of self-experience and contribute to the emergence of the disorder

The pain matrix reloaded: a salience detection system for the body

Neuroimaging and neurophysiological studies have shown that nociceptive stimuli elia salience detection system for the bodycit responses in an extensive cortical network including somatosensory, insular and cingulate areas, as well as frontal and parietal areas. This network, often referred to as the "pain matrix", is viewed as representing the activity by which the intensity and unpleasantness of the perception elicited by a nociceptive stimulus are represented. However, recent experiments have reported (i) that pain intensity can be dissociated from the magnitude of responses in the "pain matrix", (ii) that the responses in the "pain matrix" are strongly influenced by the context within which the nociceptive stimuli appear, and (iii) that non-nociceptive stimuli can elicit cortical responses with a spatial configuration similar to that of the "pain matrix". For these reasons, we propose an alternative view of the functional significance of this cortical network, in which it reflects a system involved in detecting, orienting attention towards, and reacting to the occurrence of salient sensory events. This cortical network might represent a basic mechanism through which significant events for the body's integrity are detected, regardless of the sensory channel through which these events are conveyed. This function would involve the construction of a multimodal cortical representation of the body and nearby space. Under the assumption that this network acts as a defensive system signaling potentially damaging threats for the body, emphasis is no longer on the quality of the sensation elicited by noxious stimuli but on the action prompted by the occurrence of potential threats