The man who lost his body: Suboptimal multisensory integration yields body awareness problems after a right temporoparietal brain tumour

Reports on patients who lack ownership over their entire body are extremely rare. Here, we present patient SA who suffered from complete body disownership after a tumour resection in the right temporoparietal cortex. Neuropsychological assessment disclosed selective bilateral ownership problems, despite intact primary visual and somatosensory senses. SA's disownership seems to stem from a suboptimal multimodal integration, as shown by the rubber hand illusion and the beneficial effect during and after simple exercises aiming at multisensory recalibration.     

The multisensory basis of the self: From body to identity to others

By grounding the self in the body, experimental psychology has taken the body as the starting point for a science of the self. One fundamental dimension of the bodily self is the sense of body ownership that refers to the special perceptual status of one’s own body, the feeling that “my body” belongs to me. The primary aim of this review article is to highlight recent advances in the study of body ownership and our understanding of the underlying neurocognitive processes in three ways. I first consider how the sense of body ownership has been investigated and elucidated in the context of multisensory integration. Beyond exteroception, recent studies have considered how this exteroceptively driven sense of body ownership can be linked to the other side of embodiment, that of the unobservable, yet felt, interoceptive body, suggesting that these two sides of embodiment interact to provide a unifying bodily self. Lastly, the multisensorial understanding of the self has been shown to have implications for our understanding of social relationships, especially in the context of self–other boundaries. Taken together, these three research strands motivate a unified model of the self inspired by current predictive coding models.     

Illusory hand ownership in a patient with personal neglect for the upper limb,but no somatoparaphenia

The symptoms of patients with left personal neglect are characterized by inattention towards contralesional (left) body parts while at the same time explicitly ascertaining ownership for the neglected hemibody. It is currently unknown if personal neglect is associated with more subtle or implicit disturbances of own body perception and body ownership as measured with the rubber hand illusion. In this study, we report data from a patient with a right hemispheric lesion and personal neglect, without associated somatosensory deficits. We administered to the patient (and to 12 age‐matched controls) the rubber hand illusion paradigm to the right and left hands, to elicit illusory ownership for a fake hand, before and after recovery from personal neglect for the left arm. In a first session, run when the patient showed personal neglect affecting the left arm, he experienced a significantly enhanced subjective illusion of embodiment for the left fake hand as compared to the right hand (as assessed through a standard questionnaire). After recovery from personal neglect for the left arm (second session), the results of the left and right rubber hand illusion experiments were comparable, with no modulation of hand ownership. We argue that personal neglect may consist not only in an inattentional disorder, but also in a deficit of multisensory body representation characterized by a high sensitivity to experimental manipulations of subjective aspects of body ownership.     

Body ownership: When feeling and knowing diverge

Individuals with the peculiar disturbance of ‘overcompleteness’ experience an intense desire to amputate one of their healthy limbs, describing a sense of disownership for it (Body Integrity Identity Disorder – BIID). This condition is similar to somatoparaphrenia, the acquired delusion that one’s own limb belongs to someone else. In ten individuals with BIID, we measured skin conductance response to noxious stimuli, delivered to the accepted and non-accepted limb, touching the body part or simulating the contact (stimuli approach the body without contacting it), hypothesizing that these individuals have responses like somatoparaphrenic patients, who previously showed reduced pain anticipation, when the threat was directed to the disowned limb. We found reduced anticipatory response to stimuli approaching, but not contacting, the unwanted limb. Conversely, stimuli contacting the non-accepted body-part, induced stronger SCR than those contacting the healthy parts, suggesting that feeling of ownership is critically related to a proper processing of incoming threats.     

自我表征的可塑性:基于橡胶手错觉的研究

自我识别是人类自我觉知的行为标记。传统方法认为稳定的自我表征是自我识别的基础。随着对橡胶手错觉及一系列自我表征和自我识别错觉的揭示,这一能让人将外部客体感知为自身一部分的错觉研究使得我们能够以多感官整合的方式来研究自我表征和自我识别。拥有感和自主感被认为是我们进行自我识别的两类基本体验,本文对一系列橡胶手错觉范式研究的系统回顾表明,拥有感和自主感会发生改变,这说明人的自我表征是可变的和可塑的。     

Embodiment and Animality

The aim of this article is to examine the problematic frontier that separates the phenomenology of the body and the phenomenology of animality. The main difficulty is to differentiate phenomenologically not only between embodiment and animality, but also between specifically human embodied experience and what is accessible to us through empathy in relation to the corporeality of the animal. I will tackle these questions by considering relevant textual material from the writings of Edmund Husserl and Martin Heidegger. On the one hand, I will show that although embodiment and animality are convergent on the level of the naturalistic attitude in Husserl’s Ideas II, they are divergent as soon as we place ourselves in the personalistic attitude, where the body enters into a different conjunction—namely, with the idea of person and of the spiritual world. On the other hand, Heidegger claims that, in spite of the abysmal bodily kinship with the animal, there is an essential difference between the human body and the animal organism, thus opposing the tendencies to humanize the animal and to animalize the human.     

Self awareness and the body image

What mental representations give us the sense of our body as a unique object in the world? We investigated this issue in the context of the rubber hand illusion (RHI), an illusion of body image in which a prosthetic hand brushed synchronously, but not asynchronously, with one’s own hand is perceived as actually being one’s hand. We conducted a large-scale study of the RHI, and used psychometric analysis to reveal the structure of the subjective experience of embodiment [Longo et al. (2008). What is embodiment? A psychometric approach. Cognition,107, 978-998]. Here, we use this dataset to investigate the relation between incorporation of a rubber hand into the body image and the perceived similarity between the participant’s hand and the rubber hand. Objective similarity (as measured by skin luminance, hand shape, and third-person similarity ratings) did not appear to influence participants’ experience of the RHI. Conversely, incorporation of the rubber hand into the body image did affect the similarity that participants perceived between their own hand and the rubber hand. Participants who had experienced the RHI perceived their hand and the rubber hand as significantly more similar than participants who had not experienced the illusion. That is, embodiment leads to perceived similarity, but perceived similarity does not lead to embodiment. Furthermore, similarity ratings following the illusion were selectively correlated with some components of embodiment, but not with others. These results suggest an important role of a mental body image in the perception of the relation between the self and others.     

The role of distance from the body and distance from the real hand in ownership and disownership during the rubber hand illusion

A key tool for investigating body ownership is the rubber hand illusion, in which synchronous multisensory feedback can induce feelings of ownership over a fake hand. Much research in the field aims to tease apart the mechanisms that underlie this phenomenon. Currently there is conflicting evidence as to whether increasing the distance between the real and fake hands (within reaching space) can reduce the illusion. The current study examines this further by modulating, not only the absolute distance between the real and fake hands but also their relative distance from body midline. It is found that the strength of the illusion is reduced only when the fake hand is both far from the real hand and far from the trunk; illusion scores over a fake hand in the same position can then be increased by moving the real hand nearer. This is related to peripersonal space surrounding the trunk and the hand. Subjective disownership of the real hand, and proprioceptive drift measures were also taken and may be driven by different mechanisms.     

The Feeling of Bodily Ownership

In certain startling neurological and psychiatric conditions, what is ordinarily most intimate and familiar to us—our own body—can feel alien. For instance, in cases of somatoparaphrenia subjects misattribute their body parts to others, while in cases of depersonalization subjects feel estranged from their bodies. These ownership disorders thus appear to consist in a loss of any feeling of bodily ownership, the felt sense we have of our bodies as our own. Against this interpretation of ownership disorders, I defend Sufficiency, the thesis that every experience of bodily awareness suffices for a feeling of bodily ownership. Since Sufficiency conflicts with a face-value interpretation of these ownership disorders, the burden is on me to explain away the apparent tension. To do so, I identify and correct what I believe to be the fundamental mistake in the extant literature on the feeling of bodily ownership, namely the tendency to treat the notion of a feeling of bodily ownership as a single psychological construct. Instead, I distinguish the feeling of minimal ownership, the first-personal character of bodily awareness, from the feeling of affective ownership, the distinctive type of felt concern we have for our bodies. I motivate this distinction by raising the disownership puzzle, the fact that subjects suffering from ownership disorders display an ambiguous set of symptoms, arguing the distinction I draw between minimal and affective ownership is just what is required to resolve the puzzle.     

Beyond the colour of my skin: How skin colour affects the sense of body-ownership

Multisensory stimulation has been shown to alter the sense of body-ownership. Given that perceived similarity between one's own body and those of others is crucial for social cognition, we investigated whether multisensory stimulation can lead participants to experience ownership over a hand of different skin colour. Results from two studies using introspective, behavioural and physiological methods show that, following synchronous visuotactile (VT) stimulation, participants can experience body-ownership over hands that seem to belong to a different racial group. Interestingly, a baseline measure of implicit racial bias did not predict whether participants would experience the RHI, but the overall strength of experienced body-ownership seemed to predict the participants' post-illusion implicit racial bias with those who experienced a stronger RHI showing a lower bias. These findings suggest that multisensory experiences can override strict ingroup/outgroup distinctions based on skin colour and point to a key role for sensory processing in social cognition.     

控制和外界客体社会效价对身体拥有感的影响

研究采用运动橡胶手错觉范式,操纵了“控制”和“社会效价”两个变量,通过行为实验探讨了控制和社会效价对身体拥有感的影响。结果发现,与“被动控制”条件相比,“主动控制”条件产生了更强的拥有感; 与“不利”条件相比,“有利”条件产生了更强的拥有感。且“控制”和“社会效价”的交互作用显著:无论哪种控制条件,有利条件下的拥有感都显著高于不利条件下的拥有感; 无论哪种效价条件,主动控制条件下的拥有感均显著高于被动控制条件下的拥有感。该结果表明,控制和社会效价是产生身体拥有感的条件。研究结果为提高假肢佩戴者对假肢的心理接纳程度提供了有益的训练途径。     

Embodied prosthetic arm stabilizes body posture,while unembodied one perturbs it

Senses of ownership (this arm belongs to me) and agency (I am controlling this arm) originate from sensorimotor system. External objects can be integrated into the sensorimotor system following long-term use, and recognized as one’s own body. We examined how an (un)embodied prosthetic arm modulates whole-body control, and assessed the components of prosthetic embodiment. Nine unilateral upper-limb amputees participated. Four frequently used their prosthetic arm, while the others rarely did. Their postural sway was measured during quiet standing with or without their prosthesis. The frequent users showed greater sway when they removed the prosthesis, while the rare users showed greater sway when they fitted the prosthesis. Frequent users reported greater everyday feelings of postural stabilization by prosthesis and a larger sense of agency over the prosthesis. We suggest that a prosthetic arm maintains or perturbs postural control, depending on the prosthetic embodiment, which involves sense of agency rather than ownership.     

论权利与义务的关系

权利与义务的关系可以归结为两种相关性。一种是一个人的权利与他人的义务的关系:一个人的权利,必然是他人的义务;反之亦然。这是一个人的权利与他人的义务的必然的、客观的、事实如何的关系,亦即所谓“权利与义务的逻辑相关性”。另一种则是基于这种逻辑相关性的“权利义务道德相关性”,亦即一个人的权利应该是对他自己的义务的交换:一个人所享有的权利应该等于他所负有的义务;而他所行使的权利则应该至多等于他所履行的义务。     

No-Self and the Phenomenology of Ownership

The Abhidharma Buddhist revisionary metaphysics aims to provide an intellectually and morally preferred picture of the world that lacks a self. The first part of the paper claims that the Abhidharma ‘no-self’ view can be plausibly interpreted as a no-ownership view, according to which there is no locus or subject of experience and thus no owner of mental or bodily awarenesses. On this interpretation of the no-self view, the Abhidharma Buddhist metaphysicians are committed to denying the ownership of experiences, and thereby apparently obliged to explain our purported experience of ownership. My experiences seemingly come with the sense that I am the one who is undergoing this experience. But is there a really an experience of ownership—namely, an experience of being a subject that underlies our sense of ownership? I argue that there is nothing that it is like to be an owner of experiences, in the sense that there is no experiential phenomenology associated with the ownership of experience. The second part of the paper argues that, since there is no experience of ownership, there is no onus on the Abhidharma philosopher to give an explanation of the sense of ownership.     

The Rubber Hand Illusion: two's a company, but three's a crowd

On the one hand, it is often assumed that the Rubber Hand Illusion (RHI) is constrained by a structural body model so that one cannot implement supernumerary limbs. On the other hand, several recent studies reported illusory duplication of the right hand in subjects exposed to two adjacent rubber hands. The present study tested whether spatial constraints may affect the possibility of inducing the sense of ownership to two rubber hands located side by side to the left of the subject's hand. We found that only the closest rubber hand appeared both objectively (proprioceptive drift) and subjectively (ownership rating) embodied. Crucially, synchronous touch of a second, but farther, rubber hand disrupted the objective measure of the RHI, but not the subjective one. We concluded that, in order to elicit a genuine RHI for multiple rubber hands, the two rubber hands must be at the same distance from the subject's hand/body.     

Bodily Disorientation and Moral Change

Neglect of the moral promise of disorientation is a persistent gap in even the most sophisticated philosophies of embodiment. In this article, I begin to correct this neglect by expanding our sense of the range and nature of disoriented experience and proposing new visions of disorientation as benefiting moral agency. Disorientations are experienced through complex interactions of corporeal, affective, and cognitive processes, and are characterized by feelings of shock, surprise, unease, and discomfort; felt disorientations almost always make us unsure of how to go on. I argue that experiences of disorientation can strengthen the moral agency of individuals. I begin by clarifying experiences of felt ease and orientation. I then characterize disoriented embodiment by investigating select experiences that often involve or accompany disorientation, focusing throughout on how disorientation prompts changes in motivation and action. I conclude by charting how disoriented embodiments can help individuals become better moral agents overall, in part by challenging norms that restrict embodiment and undermining dualistic conceptions of the self.     

Sense of body and sense of action both contribute to self-recognition

Recognizing oneself, easy as it appears to be, seems at least to require awareness of one's body and one's actions. To investigate the contribution of these factors to self-recognition, we presented normal subjects with an image of both their own and the experimenter's hand. The hands could make the same, a different or no movement and could be displayed in various orientations. Subjects had to tell whether the indicated hand was theirs or not. The results showed that a congruence between visual signals and signals indicating the position of the body is one component on which self-recognition is based. Recognition of one's actions is another component. Subjects had most difficulty in recognizing their hand when movements were absent. When the two hands made different movements, subjects relied exclusively on the movement cue and recognition was almost perfect. Our findings are in line with pathological alterations in the sense of body and the sense of action.     

橡胶手错觉:拥有感研究的实验范式及其应用

橡胶手错觉是一种健康个体将非肉体的假手视为自己真实身体的一部分的体验, 这种错觉可以通过同时轻刷被试面前可见的橡胶手及其不可见的真手而产生.橡胶手错觉已成为一种研究身体拥有感的重要范式, 其产生机制可以分为“自下而上的认知匹配”与“自上而下的认知匹配”两种加工方式.前者涉及视觉与触觉刺激的同步性; 而后者涉及被试心中预存的身体意象与身体图式(包括真假手之间模态特征,位置空间的相似性).综合上述证据, 身体模型假说与个人边缘空间理论进一步为拥有感产生的复杂机制提供了整合两种加工方式的解释.橡胶手错觉范式已经被用于探索精神分裂症患者等特殊被试病理分析,错觉产生和心理特质之间的关系, 以及神经外科和术后恢复上.未来的研究应该更加重视范式本身的拓展, 应用虚拟现实技术来提高身体模态的仿真效果, 利用橡胶手拥有感的易感性作为筛选与预测身体意象障碍疾病的指标.     

A model of the synchronic self

The phenomenology of the self includes the sense of control over one's body and mind, of being bounded in body and mind, of having perspective from within one's body and mind and of being extended in time. I argue that this phenomenology is to be accounted for by a set of five dissociable cognitive capacities that compose the self. The focus of this paper is on the four capacities that compose the synchronic self: the agentive(B) self, which underlies the sense of control over one's body; the boundary(B) self, which underlies the sense of being bounded within one's body; the agentive(M) self which underlies the sense of control over one's thoughts; and the boundary(M) self which underlies the sense of being bounded within one's mind. I model the agentive(B) and agentive(M) selves as parts of the motor control system and the boundary(B) self as the capacity to form and integrated map of the body. I point to the delusion of thought broadcast as a possible source of evidence for future research on the boundary(M) self.     

Evidence for a Disturbance of the Body Schema in Neglect

Subjects with left neglect often fail to use and, in some instances, recognize the left side of the body. We performed a series of investigations to determine if this deficit is, at least in part, attributable to an impairment in the “body schema,” an internal three-dimensional, dynamic representation of the spatial and biomechanical properties of one's body. First, subjects were shown a series of pictures of a single hand and asked to determine if the stimulus was a right or left hand. Subjects with neglect but not other subjects with brain lesions identified pictures of left (contralesional) hands significantly less reliably than pictures of right hands. On the basis of evidence demonstrating that the identification of pictured hands involves the matching of the stimuli to an on-line mental representation of one's body, these data suggest that neglect may be associated with a disruption of, or failure to attend to, the body schema. Data from subsequent investigations contrasting patients with left neglect and Gerstmann's syndrome argue for a distinction between a body schema and a “body image,” or conceptual representation of the body which articulates with language.