Journal articles on the topic 'Body illusion'
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1
Metral, Morgane, Corentin Gonthier, Marion Luyat, and Michel Guerraz. "Body Schema Illusions: A Study of the Link between the Rubber Hand and Kinesthetic Mirror Illusions through Individual Differences." BioMed Research International 2017 (2017): 1–10. http://dx.doi.org/10.1155/2017/6937328.
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Background. The well-known rubber hand paradigm induces an illusion by having participants feel the touch applied to a fake hand. In parallel, the kinesthetic mirror illusion elicits illusions of movement by moving the reflection of a participant’s arm. Experimental manipulation of sensory inputs leads to emergence of these multisensory illusions. There are strong conceptual similarities between these two illusions, suggesting that they rely on the same neurophysiological mechanisms, but this relationship has never been investigated. Studies indicate that participants differ in their sensitivity to these illusions, which provides a possibility for studying the relationship between these two illusions. Method. We tested 36 healthy participants to confirm that there exist reliable individual differences in sensitivity to the two illusions and that participants sensitive to one illusion are also sensitive to the other. Results. The results revealed that illusion sensitivity was very stable across trials and that individual differences in sensitivity to the kinesthetic mirror illusion were highly related to individual differences in sensitivity to the rubber hand illusion. Conclusions. Overall, these results support the idea that these two illusions may be both linked to a transitory modification of body schema, wherein the most sensitive people have the most malleable body schema.
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Vorobeva, V. P., O. S. Perepelkina, and G. A. Arina. "Equivalence of the Classical Rubber Hand Illusion and the Virtual Hand Illusion." Experimental Psychology (Russia) 13, no. 3 (2020): 31–45. http://dx.doi.org/10.17759/exppsy.2020130303.
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Computer technologies implementation into the body illusions research is increasing because they allow to controllably model complex processes that cannot be realised in ordinary life. It was previously demonstrated that the rubber hand illusion may be reconstructed in the virtual setting and cause similar changes in the somatoperception when the virtual hand begins to feel like your own. This result suggests that the phenomenological experience obtained in the classical illusion and in its virtual reality version has much in common. However, a direct experimental comparison of the two illusion variants has not been made, therefore, in this research we studied the equivalence of the rubber and virtual hand illusions (RHI and VHI). The sample consisted of 16 subjects (18—25 years). As registration methods we used a subjective sense of ownership of an artificial limb and the proprioceptive drift of the real hand towards the illusory hand. The analysis has proved the equivalence of illusions.
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Swinkels, Lieke M. J., Harm Veling, and Hein T. van Schie. "The Redundant Signals Effect and the Full Body Illusion: not Multisensory, but Unisensory Tactile Stimuli Are Affected by the Illusion." Multisensory Research 34, no. 6 (April 9, 2021): 553–85. http://dx.doi.org/10.1163/22134808-bja10046.
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Abstract During a full body illusion (FBI), participants experience a change in self-location towards a body that they see in front of them from a third-person perspective and experience touch to originate from this body. Multisensory integration is thought to underlie this illusion. In the present study we tested the redundant signals effect (RSE) as a new objective measure of the illusion that was designed to directly tap into the multisensory integration underlying the illusion. The illusion was induced by an experimenter who stroked and tapped the participant’s shoulder and underarm, while participants perceived the touch on the virtual body in front of them via a head-mounted display. Participants performed a speeded detection task, responding to visual stimuli on the virtual body, to tactile stimuli on the real body and to combined (multisensory) visual and tactile stimuli. Analysis of the RSE with a race model inequality test indicated that multisensory integration took place in both the synchronous and the asynchronous condition. This surprising finding suggests that simultaneous bodily stimuli from different (visual and tactile) modalities will be transiently integrated into a multisensory representation even when no illusion is induced. Furthermore, this finding suggests that the RSE is not a suitable objective measure of body illusions. Interestingly however, responses to the unisensory tactile stimuli in the speeded detection task were found to be slower and had a larger variance in the asynchronous condition than in the synchronous condition. The implications of this finding for the literature on body representations are discussed.
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Guterstam, Arvid, Kelly L. Collins, Jeneva A. Cronin, Hugo Zeberg, Felix Darvas, Kurt E. Weaver, Jeffrey G. Ojemann, and H. Henrik Ehrsson. "Direct Electrophysiological Correlates of Body Ownership in Human Cerebral Cortex." Cerebral Cortex 29, no. 3 (November 14, 2018): 1328–41. http://dx.doi.org/10.1093/cercor/bhy285.
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Abstract Over the past decade, numerous neuroimaging studies based on hemodynamic markers of brain activity have examined the feeling of body ownership using perceptual body-illusions in humans. However, the direct electrophysiological correlates of body ownership at the cortical level remain unexplored. To address this, we studied the rubber hand illusion in 5 patients (3 males and 2 females) implanted with intracranial electrodes measuring cortical surface potentials. Increased high-γ (70–200 Hz) activity, an index of neuronal firing rate, in premotor and intraparietal cortices reflected the feeling of ownership. In both areas, high-γ increases were intimately coupled with the subjective illusion onset and sustained both during and in-between touches. However, intraparietal activity was modulated by tactile stimulation to a higher degree than the premotor cortex through effective connectivity with the hand-somatosensory cortex, which suggests different functional roles. These findings constitute the first intracranial electrophysiological characterization of the rubber hand illusion and extend our understanding of the dynamic mechanisms of body ownership.
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Kishore, Sameer, Mar González-Franco, Christoph Hintemüller, Christoph Kapeller, Christoph Guger, Mel Slater, and Kristopher J. Blom. "Comparison of SSVEP BCI and Eye Tracking for Controlling a Humanoid Robot in a Social Environment." Presence: Teleoperators and Virtual Environments 23, no. 3 (October 1, 2014): 242–52. http://dx.doi.org/10.1162/pres_a_00192.
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Recent advances in humanoid robot technologies have made it possible to inhabit a humanlike form located at a remote place. This allows the participant to interact with others in that space and experience the illusion that the participant is actually present in the remote space. Moreover, with these humanlike forms, it may be possible to induce a full-body ownership illusion, where the robot body is perceived to be one's own. We show that it is possible to induce the full-body ownership illusion over a remote robotic body with a highly robotic appearance. Additionally, our results indicate that even with nonmanual control of a remote robotic body, it is possible to induce feelings of agency and illusions of body ownership. Two established control methods, an SSVEP-based BCI and eye tracking, were tested as a means of controlling the robot's gesturing. Our experience and the results indicate that both methods are tractable for immersive control of a humanoid robot in a social telepresence setting.
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Preston, Catherine, and Roger Newport. "How Long is Your Arm? Using Multisensory Illusions to Modify Body Image from the Third Person Perspective." Perception 41, no. 2 (January 1, 2012): 247–49. http://dx.doi.org/10.1068/p7103.
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Updating body representations from the 3rd person perspectives (3PP) seems to require viewing the real body, unlike when viewing from a 1st person perspective. Here, 3PP updating was investigated through induction of a physically impossible multisensory illusion in which participants viewed real-time 3PP video of themselves having their arm pulled until it stretched to twice its normal length. The illusion elicited the subjective experience that the participant's own arm had been stretched and caused an overestimation of reaching distance, although actual reaches were unaffected. Multisensory illusions from the 3PP can alter body image when applied to real bodies.
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Cadete, Denise, and Matthew R. Longo. "A Continuous Illusion of Having a Sixth Finger." Perception 49, no. 8 (July 16, 2020): 807–21. http://dx.doi.org/10.1177/0301006620939457.
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Our body is central to our sense of self and personal identity, yet it can be manipulated in the laboratory in surprisingly easy ways. Several multisensory illusions have shown the flexibility of the mental representation of our bodies by inducing the illusion of owning an artificial body part or having a body part with altered features. Recently, new studies showed we can embody additional body parts such as a supernumerary finger. Newport et al. recently reported a novel six-finger illusion using conflicting visual and tactile signals induced with the mirror box to create the illusory perception of having a sixth finger for a brief moment. In this study, we aimed to replicate this result and to investigate whether the experience of embodiment of a sixth finger could be prolonged for an extended duration by applying continuous visual–tactile stimulation. Results showed that a continuous illusion of having a sixth finger can be clearly induced. This shows that the six-finger illusion does not reflect merely a momentary confusion due to conflicting multisensory signals but can reflect an enduring representation of a supernumerary finger.
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Holmes, Nicholas P., Tamar R. Makin, Michelle Cadieux, Claire Williams, Katherine R. Naish, Charles Spence, and David I. Shore. "Hand ownership and hand position in the rubber hand illusion are uncorrelated." Seeing and Perceiving 25 (2012): 52. http://dx.doi.org/10.1163/187847612x646730.
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The rubber hand illusion (RHI) is a multisensory (visual, tactile, proprioceptive) illusion in which participants report body ownership over, mislocalize actual hand position to, and feel touches applied to, the rubber hand. For many years, researchers have used changes in perceived hand position, measured by inter-manual pointing, as a more objective measure of the illusion than verbal reports alone. Despite this reliance, there is little evidence to show that the illusion of hand ownership is directly related to perceived hand position. We developed an adaptive staircase procedure to measure perceived hand position, and tested whether the RHI affected perceived hand position. In two experiments we found a significant illusion of ownership, as well as significant changes in perceived hand position, but these two measures were uncorrelated. In a third experiment using more typical RHI procedures, we again replicated significant illusions of ownership and changes in hand position, but again the measures were uncorrelated. We conclude that viewing and feeling touches applied to a dummy hand results in clear illusions of ownership and changes in hand position, but via independent mechanisms.
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Holmes, Nicholas Paul, and Charles Spence. "Dissociating body image and body schema with rubber hands." Behavioral and Brain Sciences 30, no. 2 (April 2007): 211–12. http://dx.doi.org/10.1017/s0140525x07001501.
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AbstractDijkerman & de Haan (D&dH) argue that body image and body schema form parts of different and dissociable somatosensory streams. We agree in general, but believe that more emphasis should be placed on interactions between these two streams. We illustrate this point with evidence from the rubber-hand illusion (RHI) – an illusion of body image, which depends critically upon body schema.
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Sciortino, Placido, and Christoph Kayser. "The rubber hand illusion is accompanied by a distributed reduction of alpha and beta power in the EEG." PLOS ONE 17, no. 7 (July 29, 2022): e0271659. http://dx.doi.org/10.1371/journal.pone.0271659.
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Previous studies have reported correlates of bodily self-illusions such as the rubber hand in signatures of rhythmic brain activity. However, individual studies focused on specific variations of the rubber hand paradigm, used different experimental setups to induce this, or used different control conditions to isolate the neurophysiological signatures related to the illusory state, leaving the specificity of the reported illusion-signatures unclear. We here quantified correlates of the rubber hand illusion in EEG-derived oscillatory brain activity and asked two questions: which of the observed correlates are robust to the precise nature of the control conditions used as contrast for the illusory state, and whether such correlates emerge directly around the subjective illusion onset. To address these questions, we relied on two experimental configurations to induce the illusion, on different non-illusion conditions to isolate neurophysiological signatures of the illusory state, and we implemented an analysis directly focusing on the immediate moment of the illusion onset. Our results reveal a widespread suppression of alpha and beta-band activity associated with the illusory state in general, whereby the reduction of beta power prevailed around the immediate illusion onset. These results confirm previous reports of a suppression of alpha and beta rhythms during body illusions, but also highlight the difficulties to directly pinpoint the precise neurophysiological correlates of the illusory state.
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Fang, Wen, Junru Li, Guangyao Qi, Shenghao Li, Mariano Sigman, and Liping Wang. "Statistical inference of body representation in the macaque brain." Proceedings of the National Academy of Sciences 116, no. 40 (September 3, 2019): 20151–57. http://dx.doi.org/10.1073/pnas.1902334116.
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The sense of one’s own body is a pillar of self-consciousness and could be investigated by inducing human illusions of artificial objects as part of the self. Here, we present a nonhuman primate version of a rubber-hand illusion that allowed us to determine its computational and neuronal mechanisms. We implemented a video-based system in a reaching task in monkeys and combined a casual inference model to establish an objective and quantitative signature for the monkey’s body representation. Similar to humans, monkeys were more likely to perceive an external object as part of the self when the dynamics (spatial disparity) and the features (shape and structure) of visual (V) input was closer to proprioceptive (P) signals. Neural signals in the monkey’s premotor cortex reflected the strength of illusion and the likelihood of misattributing the illusory hand to oneself, thus, revealing a cortical representation of body ownership.
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Lee, San Ho, Gi-Eun Lee, and Jang-Han Lee. "An exploratory study on the effect of mental rehearsal on the virtual body swapping illusion." Korean Data Analysis Society 24, no. 3 (June 30, 2022): 943–54. http://dx.doi.org/10.37727/jkdas.2022.24.3.943.
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The body swapping illusion is a perceptual phenomenon in which one perceives a virtual (or another) body as being one’s own. The aim of this study was to investigate the effects of mental rehearsal on the generation of the body swapping illusion. Participants were 58 male undergraduate students. Participants were randomly assigned to either the physical rehearsal (n=20), mental rehearsal (n=18), or control condition (n=20). There were no significant differences in state and trait anxiety, simulator sickness, or immersive tendencies between groups, but there were significant differences in the body swapping illusion and a sense of presence between conditions. Subsequent post-hoc analyses revealed that the body swapping illusion was significantly greater in the physical and mental rehearsal conditions than the control condition, and the sense of presence was significantly greater in the physical rehearsal than in the control condition. In conclusion, we found that mental rehearsal exerted similar effects as physical rehearsal ingenerating the illusion of body swapping. This suggests that generating the illusion of body swapping through mental rehearsal may be applicable in clinical settings.
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Seo, Min-Hee, Jeh-Kwang Ryu, Byung-Cheol Kim, Sang-Bin Jeon, and Kyoung-Min Lee. "Persistence of metric biases in body representation during the body ownership illusion." PLOS ONE 17, no. 7 (July 26, 2022): e0272084. http://dx.doi.org/10.1371/journal.pone.0272084.
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Our perception of the body’s metric is influenced by bias according to the axis, called the systematic metric bias in body representation. Systematic metric bias was first reported as Weber’s illusion and observed in several parts of the body in various patterns. However, the systematic metric bias was not observed with a fake hand under the influence of the body ownership illusion during the line length judgment task. The lack of metric bias observed during the line length judgment task with a fake hand implies that the tactile modality occupies a relatively less dominant position than perception occurring through the real body. The change in weight between visual and tactile modalities during the body ownership illusion has not been adequately investigated yet, despite being a factor that influences the perception through body ownership illusion. Therefore, this study aimed to investigate whether the dominance of vision over tactile modality is prominent, regardless of the task type. To investigate whether visual dominance persists during the process of inducing body ownership illusion regardless of task type, we introduced spatial visuotactile incongruence (2 cm, 3 cm) in the longitudinal and transverse axes during the visuotactile localization tasks and measured the intensity of the body ownership illusion using a questionnaire. The results indicated that participants perceived smaller visuotactile incongruence when the discrepancy occurred in the transverse axis rather than in the longitudinal axis. The anisotropy in the tolerance of visuotactile incongruence implies the persistence of metric biases in body representation. The results suggest the need for further research regarding the factors influencing the weight of visual and tactile modalities.
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Truong, S., R. Zopf, M. Finkbeiner, J. Friedman, and M. Williams. "Perceptual Body Illusion Affects Action." Journal of Vision 10, no. 7 (August 13, 2010): 1052. http://dx.doi.org/10.1167/10.7.1052.
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Kodaka, Kenri, and Ayaka Kanazawa. "Innocent Body-Shadow Mimics Physical Body." i-Perception 8, no. 3 (May 1, 2017): 204166951770652. http://dx.doi.org/10.1177/2041669517706520.
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The paradigm of the rubber hand illusion was applied to a shadow to determine whether the body-shadow is a good candidate for the alternative belonging to our body. Three kinds of shadows, a physical hand, a hand-shaped cloth, and a rectangle cloth, were tested for this purpose. The questionnaire results showed that both anatomical similarity and visuo-proprioception correlation were effective in enhancing illusory ownership of the shadow. According to the proprioceptive drift measurement, whether the shadow purely originated from the physical body was a critical factor in yielding the significantly positive drift. Thus, results demonstrated that the shadow can distort illusory ownership with the rubber hand illusion paradigm, but the proprioception was clearly distorted only when the body-shadow was purely applied. This implies the presence of special cognitive processing to discriminate the self-body shadow from the others.
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Choi, Woong, Liang Li, Satoru Satoh, and Kozaburo Hachimura. "Multisensory Integration in the Virtual Hand Illusion with Active Movement." BioMed Research International 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/8163098.
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Improving the sense of immersion is one of the core issues in virtual reality. Perceptual illusions of ownership can be perceived over a virtual body in a multisensory virtual reality environment. Rubber Hand and Virtual Hand Illusions showed that body ownership can be manipulated by applying suitable visual and tactile stimulation. In this study, we investigate the effects of multisensory integration in the Virtual Hand Illusion with active movement. A virtual xylophone playing system which can interactively provide synchronous visual, tactile, and auditory stimulation was constructed. We conducted two experiments regarding different movement conditions and different sensory stimulations. Our results demonstrate that multisensory integration with free active movement can improve the sense of immersion in virtual reality.
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Bottiroli, Sara, Marta Matamala-Gomez, Marta Allena, Elena Guaschino, Natascia Ghiotto, Roberto De Icco, Grazia Sances, and Cristina Tassorelli. "The Virtual “Enfacement Illusion” on Pain Perception in Patients Suffering from Chronic Migraine: A Study Protocol for a Randomized Controlled Trial." Journal of Clinical Medicine 11, no. 22 (November 21, 2022): 6876. http://dx.doi.org/10.3390/jcm11226876.
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Background: given the limited efficacy, tolerability, and accessibility of pharmacological treatments for chronic migraine (CM), new complementary strategies have gained increasing attention. Body ownership illusions have been proposed as a non-pharmacological strategy for pain relief. Here, we illustrate the protocol for evaluating the efficacy in decreasing pain perception of the enfacement illusion of a happy face observed through an immersive virtual reality (VR) system in CM. Method: the study is a double-blind randomized controlled trial with two arms, involving 100 female CM patients assigned to the experimental group or the control group. The experimental group will be exposed to the enfacement illusion, whereas the control group will be exposed to a pleasant immersive virtual environment. Both arms of the trial will consist in three VR sessions (20 min each). At the baseline and at the end of the intervention, the patients will fill in questionnaires based on behavioral measures related to their emotional and psychological state and their body satisfaction. Before and after each VR session, the level of pain, the body image perception, and the affective state will be assessed. Discussion: this study will provide knowledge regarding the relationship between internal body representation and pain perception, supporting the effectiveness of the enfacement illusion as a cognitive behavioral intervention in CM.
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Scarpina, Serino, Keizer, Chirico, Scacchi, Castelnuovo, Mauro, and Riva. "The Effect of a Virtual-Reality Full-Body Illusion on Body Representation in Obesity." Journal of Clinical Medicine 8, no. 9 (August 28, 2019): 1330. http://dx.doi.org/10.3390/jcm8091330.
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Background. The effective illusory ownership over an artificial body in modulating body representations in healthy and eating disorders population has been repeatedly reported in recent literature. In this study, we extended this research in the field of obesity: specifically, we investigated whether ownership over a virtual body with a skinny abdomen might be successfully experienced by participants affected by obesity. Methods. Fifteen participants with obesity and fifteen healthy-weight participants took part at this study in which the VR-Full-Body Illusion was adopted. The strength of illusion was investigated through the traditional Embodiment Questionnaire, while changes in bodily experience were measured through a body size estimation task. Results. Participants with obesity as well as healthy-weight participants reported to experience the illusion. About the body size estimation task, both groups reported changes only in the estimation of the abdomen’s circumference after the experimental condition, in absence of any another difference. Discussion. Participants with obesity reported to experience the illusion over a skinny avatar, but the modulation of the bodily experience seems controversial. Future lines of research exploiting this technique for modulating body representations in obesity, specifically in terms of potential therapeutic use, were discussed.
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Fiorio, Mirta, Caterina Mariotti, Marta Panzeri, Emanuele Antonello, Joseph Classen, and Michele Tinazzi. "The Role of the Cerebellum in Dynamic Changes of the Sense of Body Ownership: A Study in Patients with Cerebellar Degeneration." Journal of Cognitive Neuroscience 26, no. 4 (April 2014): 712–21. http://dx.doi.org/10.1162/jocn_a_00522.
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The sense of the body is deeply rooted in humans, and it can be experimentally manipulated by inducing illusions in at least two aspects: a subjective feeling of ownership and a proprioceptive sense of limb position. Previous studies mapped these different aspects onto anatomically distinct neuronal regions, with the ventral premotor cortex processing subjective experience of ownership and the inferior parietal lobule processing proprioceptive calibration. Lines of evidence suggest an involvement also of the cerebellum, but its precise role is not clear yet. To investigate the contribution of the cerebellum in the sense of body ownership, we applied the rubber-hand illusion paradigm in 28 patients affected by neurodegenerative cerebellar ataxia, selectively involving the cerebellum, and in 26 age-matched control participants. The rubber hand illusion is established by synchronous stroking of the participants' real unseen hand and a visible fake hand. Short asynchronous stroking does not bring about the illusion. We tested the subjective experience of the illusion, evaluated through a questionnaire and the proprioceptive drift of the real unseen hand toward the viewed rubber hand. In patients with cerebellar ataxia, we observed reduced sense of the subjective illusory experience specifically after synchronous stroking. In contrast, the proprioceptive drift was enhanced after synchronous and after asynchronous stimulation. These findings support the contention that the mechanisms underlying the presence of the illusion and the proprioceptive drift may be differently affected in different conditions. Impairment of the subjective sense of the illusion in cerebellar patients might hint at an involvement of cerebellar-premotor networks, whereas the proprioceptive drift typically associated with synchronous stroking appears to rely on other circuits, likely involving the cerebellum and the parietal regions.
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Butler, Annie A., Lucy S. Robertson, Audrey P. Wang, Simon C. Gandevia, and Martin E. Héroux. "Do interoception and attending to the upper limbs affect body ownership and body representation in the grasp illusion?" PLOS ONE 16, no. 11 (November 17, 2021): e0259988. http://dx.doi.org/10.1371/journal.pone.0259988.
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Passively grasping an unseen artificial finger induces ownership over this finger and an illusory coming together of one’s index fingers: a grasp illusion. Here we determine how interoceptive ability and attending to the upper limbs influence this illusion. Participants passively grasped an unseen artificial finger with their left index finger and thumb for 3 min while their right index finger, located 12 cm below, was lightly clamped. Experiment 1 (n = 30) investigated whether the strength of the grasp illusion (perceived index finger spacing and perceived ownership) is related to a person’s level of interoceptive accuracy (modified heartbeat counting task) and sensibility (Noticing subscale of the Multidimensional Assessment of Interoceptive Awareness). Experiment 2 (n = 30) investigated the effect of providing verbal or tactile cues to guide participants’ attention to their upper limbs. On their own, neither interoceptive accuracy and sensibility or verbal and tactile cueing had an effect on the grasp illusion. However, verbal cueing increased the strength of the grasp illusion in individuals with lower interoceptive ability. Across the observed range of interoceptive accuracy and sensibility, verbal cueing decreased perceived index spacing by 5.6 cm [1.91 to 9.38] (mean [95%CI]), and perceived ownership by ∼3 points on a 7-point Likert scale (slope -0.93 [-1.72 to -0.15]). Thus, attending to the upper limbs via verbal cues increases the strength of the grasp illusion in a way that is inversely proportional to a person’s level of interoceptive accuracy and sensibility.
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Critchley, Hugo D., Vanessa Botan, and Jamie Ward. "Absence of reliable physiological signature of illusory body ownership revealed by fine-grained autonomic measurement during the rubber hand illusion." PLOS ONE 16, no. 4 (April 1, 2021): e0237282. http://dx.doi.org/10.1371/journal.pone.0237282.
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The neural representation of a ‘biological self’ is linked theoretically to the control of bodily physiology. In an influential model, selfhood relates to internal agency and higher-order interoceptive representation, inferred from the predicted impact of efferent autonomic nervous activity on afferent viscerosensory feedback. Here we tested if an altered representation of physical self (illusory embodiment of an artificial hand) is accompanied by sustained shifts in autonomic activity. Participants (N = 37) underwent procedures for induction of the rubber hand illusion (synchronous stroking of own unseen hand and observed stroking of artificial hand) and a control condition (asychronous stroking). We recorded electrocardiography, electrodermal activity, and a non-invasive measure of multiunit skin sympathetic nerve activity (SKNA) from the chest. We compared these autonomic indices between task conditions, and between individuals who did and did not experience the illusion. Bayes factors quantified the strength of evidence for and against null hypotheses. Observed proprioceptive drift and subjective reports confirmed the efficacy of the synchronous (vs asynchronous) condition in inducing illusory hand ownership. Stringent discriminant analysis classified 24/37 individuals as experiencing the rubber hand illusion. Surprisingly, heart rate, heart rate variability, electrodermal activity, and SKNA measures revealed no autonomic differences between synchronous vs asynchronous conditions, nor between individuals who did or did not experience the rubber hand illusion. Bayes factors indicated substantial evidence for no physiological differences. In contrast to earlier reports, our autonomic data show the absence of a reliable change in physiological state during the rubber hand illusion. More encompassing perturbations of self-experience, for example in full body illusions, may nevertheless be coupled to, or facilitated by, changes in efferent autonomic activity and afferent viscerosensory feedback. Our findings suggest that such changes in bodily physiology are not sustained as an obligatory component of the rubber hand illusion.
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Stanton, Tasha R., Helen R. Gilpin, Louisa Edwards, G. Lorimer Moseley, and Roger Newport. "Illusory resizing of the painful knee is analgesic in symptomatic knee osteoarthritis." PeerJ 6 (July 17, 2018): e5206. http://dx.doi.org/10.7717/peerj.5206.
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Background Experimental and clinical evidence support a link between body representations and pain. This proof-of-concept study in people with painful knee osteoarthritis (OA) aimed to determine if: (i) visuotactile illusions that manipulate perceived knee size are analgesic; (ii) cumulative analgesic effects occur with sustained or repeated illusions. Methods Participants with knee OA underwent eight conditions (order randomised): stretch and shrink visuotactile (congruent) illusions and corresponding visual, tactile and incongruent control conditions. Knee pain intensity (0–100 numerical rating scale; 0 = no pain at all and 100 = worst pain imaginable) was assessed pre- and post-condition. Condition (visuotactile illusion vs control) × Time (pre-/post-condition) repeated measure ANOVAs evaluated the effect on pain. In each participant, the most beneficial illusion was sustained for 3 min and was repeated 10 times (each during two sessions); paired t-tests compared pain at time 0 and 180s (sustained) and between illusion 1 and illusion 10 (repeated). Results Visuotactile illusions decreased pain by an average of 7.8 points (95% CI [2.0–13.5]) which corresponds to a 25% reduction in pain, but the tactile only and visual only control conditions did not (Condition × Time interaction: p = 0.028). Visuotactile illusions did not differ from incongruent control conditions where the same visual manipulation occurred, but did differ when only the same tactile input was applied. Sustained illusions prolonged analgesia, but did not increase it. Repeated illusions increased the analgesic effect with an average pain decrease of 20 points (95% CI [6.9–33.1])–corresponding to a 40% pain reduction. Discussion Visuotactile illusions are analgesic in people with knee OA. Our results suggest that visual input plays a critical role in pain relief, but that analgesia requires multisensory input. That visual and tactile input is needed for analgesia, supports multisensory modulation processes as a possible explanatory mechanism. Further research exploring the neural underpinnings of these visuotactile illusions is needed. For potential clinical applications, future research using a greater dosage in larger samples is warranted.
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Pasqualotto, Achille, and Michael J. Proulx. "Two-Dimensional Rubber-Hand Illusion: The Dorian Gray Hand Illusion." Multisensory Research 28, no. 1-2 (2015): 101–10. http://dx.doi.org/10.1163/22134808-00002473.
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The rubber-hand illusion provides a window into body representation and consciousness. It has been found that body-ownership extended to numerous hand-like objects. Interestingly, the vast majority of these objects were three-dimensional. We adopted this paradigm by using hand drawings to investigate whether rubber-hand illusion could be extended to two-dimensional hand samples, and we measured skin conductance responses and behavioural variables. The fact that this illusion extended to two-dimensional stimuli reveals the dominant role of top–down information on visual perception for body representation and consciousness.
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O’Kane, Sophie H., and H. Henrik Ehrsson. "The contribution of stimulating multiple body parts simultaneously to the illusion of owning an entire artificial body." PLOS ONE 16, no. 1 (January 25, 2021): e0233243. http://dx.doi.org/10.1371/journal.pone.0233243.
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The full-body ownership illusion exploits multisensory perception to induce a feeling of ownership of an entire artificial body. Although previous research has shown that synchronous visuotactile stimulation of a single body part is sufficient for illusory ownership of the whole body, the effect of combining multisensory stimulation across multiple body parts remains unknown. Therefore, 48 healthy adults participated in a full-body ownership illusion with conditions involving synchronous (illusion) or asynchronous (control) visuotactile stimulation to one, two, or three body parts simultaneously (2×3 design). We used questionnaires to isolate illusory ownership of five specific body parts (left arm, right arm, trunk, left leg, right leg) from the full-body ownership experience and sought to test not only for increased ownership in synchronous versus asynchronous conditions but also for potentially varying degrees of full-body ownership illusion intensity related to the number of body parts stimulated. Illusory full-body ownership and all five body-part ownership ratings were significantly higher following synchronous stimulation than asynchronous stimulation (p-values < .01). Since non-stimulated body parts also received significantly increased ownership ratings following synchronous stimulation, the results are consistent with an illusion that engages the entire body. Furthermore, we noted that ownership ratings for right body parts (which were often but not always stimulated in this experiment) were significantly higher than ownership ratings for left body parts (which were never stimulated). Regarding the effect of stimulating multiple body parts simultaneously on explicit full-body ownership ratings, there was no evidence of a significant main effect of the number of stimulations (p = .850) or any significant interaction with stimulation synchronicity (p = .160), as assessed by linear mixed modelling. Instead, median ratings indicated a moderate affirmation (+1) of an illusory full-body sensation in all three synchronous conditions, a finding mirrored by comparable full-body illusion onset times. In sum, illusory full-body ownership appears to be an ‘all-or-nothing’ phenomenon and depends upon the synchronicity of visuotactile stimulation, irrespective of the number of stimulated body parts.
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Llobera, Joan, M. V. Sanchez-Vives, and Mel Slater. "The relationship between virtual body ownership and temperature sensitivity." Journal of The Royal Society Interface 10, no. 85 (August 6, 2013): 20130300. http://dx.doi.org/10.1098/rsif.2013.0300.
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In the rubber hand illusion, tactile stimulation seen on a rubber hand, that is synchronous with tactile stimulation felt on the hidden real hand, can lead to an illusion of ownership over the rubber hand. This illusion has been shown to produce a temperature decrease in the hidden hand, suggesting that such illusory ownership produces disownership of the real hand. Here, we apply immersive virtual reality (VR) to experimentally investigate this with respect to sensitivity to temperature change. Forty participants experienced immersion in a VR with a virtual body (VB) seen from a first-person perspective. For half the participants, the VB was consistent in posture and movement with their own body, and in the other half, there was inconsistency. Temperature sensitivity on the palm of the hand was measured before and during the virtual experience. The results show that temperature sensitivity decreased in the consistent compared with the inconsistent condition. Moreover, the change in sensitivity was significantly correlated with the subjective illusion of virtual arm ownership but modulated by the illusion of ownership over the full VB. This suggests that a full body ownership illusion results in a unification of the virtual and real bodies into one overall entity—with proprioception and tactile sensations on the real body integrated with the visual presence of the VB. The results are interpreted in the framework of a ‘body matrix’ recently introduced into the literature.
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Garner, David M., Maureen V. Garner, and Lawrence F. Van Egeren. "Body dissatisfaction adjusted for weight: The body illusion index." International Journal of Eating Disorders 12, no. 3 (November 1992): 263–71. http://dx.doi.org/10.1002/1098-108x(199211)12:3<263::aid-eat2260120306>3.0.co;2-q.
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Kalckert, Andreas, Ian Bico, and Jia Xi Fong. "Illusions With Hands, but Not With Balloons – Comparing Ownership and Referral of Touch for a Corporal and Noncorporal Object After Visuotactile Stimulation." Perception 48, no. 5 (April 2, 2019): 447–55. http://dx.doi.org/10.1177/0301006619839286.
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The rubber hand illusion is a perceptual illusion of perceiving an object like a model hand as part of the own body. The question whether the illusion can be induced with noncorporal objects that do not look like a human body part is not perfectly resolved yet. In this study, we directly assessed the subjective experience of two different components within the illusion (i.e., ownership and referral of touch) when a model hand and a balloon are stimulated. We observed significantly stronger illusion ratings for the hand as compared with the balloon, and only the hand ratings showed a clear affirmation of the illusion. We further conclude that (a) a significant difference between synchronous and asynchronous conditions may not be sufficient to argue for the successful induction of the illusion and (b) the subcomponents show a different pattern in the different conditions, which may lead to alternative interpretations. These observations call for a more fine-grained interpretation of questionnaire data in rubber hand illusion studies.
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IJsselsteijn, Wijnand A., Yvonne A. W. de Kort, and Antal Haans. "Is This My Hand I See Before Me? The Rubber Hand Illusion in Reality, Virtual Reality, and Mixed Reality." Presence: Teleoperators and Virtual Environments 15, no. 4 (August 1, 2006): 455–64. http://dx.doi.org/10.1162/pres.15.4.455.
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This paper presents a first study in which a recently reported intermodal perceptual illusion known as the rubber hand illusion is experimentally investigated under mediated conditions. When one's own hand is placed out of view and a visible fake hand is repeatedly stroked and tapped in synchrony with the unseen hand, subjects report a strong sense in which the fake hand is experienced as part of their own body. In our experiment, we investigated this illusion under three conditions: (i) unmediated condition, replicating the original paradigm, (ii) virtual reality (VR) condition, where both the fake hand and its stimulation were projected on the table in front of the participant, and (iii) mixed reality (MR) condition, where the fake hand was projected, but its stimulation was unmediated. Dependent measures included self-report (open-ended and questionnaire-based) and drift, that is, the offset between the felt position of the hidden hand and its actual position. As expected, the unmediated condition produced the strongest illusion, as indicated both by self-report and drift towards the rubber hand. The VR condition produced a more convincing subjective illusion than the MR condition, although no difference in drift was found between the mediated conditions. Results are discussed in terms of perceptual mechanisms underlying the rubber hand illusion, and the illusion's relevance to understanding telepresence.
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Rajabi, Majid, and Alireza Mojahed. "Acoustic Illusion and Cloaking: Active Spherical Body." Acta Acustica united with Acustica 105, no. 3 (May 10, 2019): 419–25. http://dx.doi.org/10.3813/aaa.919324.
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Yong, Ed. "Out-of-body experience: Master of illusion." Nature 480, no. 7376 (December 2011): 168–70. http://dx.doi.org/10.1038/480168a.
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Randhawa, Gursharan. "Cool hand illusion reveals mind-body link." New Scientist 199, no. 2671 (August 2008): 10. http://dx.doi.org/10.1016/s0262-4079(08)62154-5.
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Cascio, Carissa J., Jennifer H. Foss-Feig, Courtney P. Burnette, Jessica L. Heacock, and Akua A. Cosby. "The rubber hand illusion in children with autism spectrum disorders: delayed influence of combined tactile and visual input on proprioception." Autism 16, no. 4 (March 7, 2012): 406–19. http://dx.doi.org/10.1177/1362361311430404.
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In the rubber hand illusion, perceived hand ownership can be transferred to a rubber hand after synchronous visual and tactile stimulation. Perceived body ownership and self–other relation are foundational for development of self-awareness, imitation, and empathy, which are all affected in autism spectrum disorders (ASD). We examined the rubber hand illusion in children with and without ASD. Children with ASD were initially less susceptible to the illusion than the comparison group, yet showed the effects of the illusion after 6 minutes. Delayed susceptibility to the illusion may result from atypical multisensory temporal integration and/or an unusually strong reliance on proprioception. Children with ASD who displayed less empathy were significantly less likely to experience the illusion than those with more intact ability to express empathy. A better understanding of body representation in ASD may elucidate neural underpinnings of social deficits, thus informing future intervention approaches.
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Bogdan, Radu J. "The epistemological illusion." Behavioral and Brain Sciences 18, no. 2 (June 1995): 390–91. http://dx.doi.org/10.1017/s0140525x00039078.
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AbstractI argue against the mentalist view that commonsense psychology (CSP) is about the intrinsic properties of the mind, and in particular against the notion that the evidence privately or publicly available to the CS psychologists confirms the mentalist view. I suggest that the internal phenomenology of mental attitudes merely provides access to a body of procedural knowledge, and that the propositional forms of the attitudes normally summarize extensive units of procedural knowledge.
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Bertamini, Marco. "The Bathtub Illusion." i-Perception 10, no. 4 (July 2019): 204166951985359. http://dx.doi.org/10.1177/2041669519853594.
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When a person looks at the fingers of their own hand as they line up in depth, the impression may emerge that the little fingers, which are farther away, are located too far and if so they are not part of the same hand. I describe the conditions and suggest this is due to the size difference between fingers (size-distance scaling). A role of size on perceived distance here is more powerful than knowledge about our own body.
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Sadibolova, Renata, and Matthew R. Longo. "Seeing the body produces limb-specific modulation of skin temperature." Biology Letters 10, no. 4 (April 2014): 20140157. http://dx.doi.org/10.1098/rsbl.2014.0157.
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Vision of the body, even when non-informative about stimulation, affects somatosensory processing. We investigated whether seeing the body also modulates autonomic control in the periphery by measuring skin temperature while manipulating vision. Using a mirror box, the skin temperature was measured from left hand dorsum while participants: (i) had the illusion of seeing their left hand, (ii) had the illusion of seeing an object at the same location or (iii) looked directly at their contralateral right hand. Skin temperature of the left hand increased when participants had the illusion of directly seeing that hand but not in the other two view conditions. In experiment 2, participants viewed directly their left or right hand, or the box while we recorded both hand dorsum temperatures. Temperature increased in the viewed hand but not the contralateral hand. These results show that seeing the body produces limb-specific modulation of thermal regulation.
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Crucianelli, Laura, Yannis Paloyelis, Lucia Ricciardi, Paul M. Jenkinson, and Aikaterini Fotopoulou. "Embodied Precision: Intranasal Oxytocin Modulates Multisensory Integration." Journal of Cognitive Neuroscience 31, no. 4 (April 2019): 592–606. http://dx.doi.org/10.1162/jocn_a_01366.
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Multisensory integration processes are fundamental to our sense of self as embodied beings. Bodily illusions, such as the rubber hand illusion (RHI) and the size–weight illusion (SWI), allow us to investigate how the brain resolves conflicting multisensory evidence during perceptual inference in relation to different facets of body representation. In the RHI, synchronous tactile stimulation of a participant's hidden hand and a visible rubber hand creates illusory body ownership; in the SWI, the perceived size of the body can modulate the estimated weight of external objects. According to Bayesian models, such illusions arise as an attempt to explain the causes of multisensory perception and may reflect the attenuation of somatosensory precision, which is required to resolve perceptual hypotheses about conflicting multisensory input. Recent hypotheses propose that the precision of sensorimotor representations is determined by modulators of synaptic gain, like dopamine, acetylcholine, and oxytocin. However, these neuromodulatory hypotheses have not been tested in the context of embodied multisensory integration. The present, double-blind, placebo-controlled, crossover study ( n = 41 healthy volunteers) aimed to investigate the effect of intranasal oxytocin (IN-OT) on multisensory integration processes, tested by means of the RHI and the SWI. Results showed that IN-OT enhanced the subjective feeling of ownership in the RHI, only when synchronous tactile stimulation was involved. Furthermore, IN-OT increased an embodied version of the SWI (quantified as estimation error during a weight estimation task). These findings suggest that oxytocin might modulate processes of visuotactile multisensory integration by increasing the precision of top–down signals against bottom–up sensory input.
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Guterstam, Arvid, and H. Henrik Ehrsson. "Disowning one’s seen real body during an out-of-body illusion." Consciousness and Cognition 21, no. 2 (June 2012): 1037–42. http://dx.doi.org/10.1016/j.concog.2012.01.018.
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Kovyazina, M., K. Fomina, and N. Varako. "Illusion as a Research Tool for Inter-analyzer Interaction (Iai) Characteristics in a Psychiatric Clinic." European Psychiatry 41, S1 (April 2017): S634. http://dx.doi.org/10.1016/j.eurpsy.2017.01.1039.
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IntroductionIAI does not only play a functional role but also has qualitative and quantitative characteristics. Biological significance of IAI consists in mobilization of some sensory functions and demobilization of others as a response to a stimulus signaling changes in the environment. This constitutes one of the manifestations of body's preparatory reactions for action in the forthcoming situation. It has been established that in patients with psychic pathology such preparation of the body systems is affected, which may manifest through changes in illusion frequency.ObjectivesTo apply Charpentier illusion to research IAI characteristics with the purpose of further detection of abnormalities in the sphere of intermodal interaction.MethodsOne of the IAI research methods, is illusion research, e.g. Charpentier illusion, since it is based on interaction between visual and proprioceptive analyzers. Changes in preparatory reaction in subjects with psychic pathology is characterized by decline in illusion frequency, patients in these conditions should evaluate stimuli more correctly than healthy participants. Pre-experimental research design included two subjects: with white matter pathology (patient G., male, 27, full agenesis of CC, based on MRI results) and with IDD (subject A., male, 30).ResultsResearch subjects demonstrated absence of illusions, which is indicative of functional weakness of IAI, which results in inconsistency of sensory systems and meaningless perception. IAI plays an important role in formation of human psyche by enabling the development of significant patterns underlying human cognitive activity.ConclusionIllusion research is relevant for clinical psychological diagnosis of diseases associated with integrative brain activity disorders.Disclosure of interestThe authors have not supplied their declaration of competing interest.
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Pozeg, Polona, Estelle Palluel, Roberta Ronchi, Marco Solcà, Abdul-Wahab Al-Khodairy, Xavier Jordan, Ammar Kassouha, and Olaf Blanke. "Virtual reality improves embodiment and neuropathic pain caused by spinal cord injury." Neurology 89, no. 18 (October 6, 2017): 1894–903. http://dx.doi.org/10.1212/wnl.0000000000004585.
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Objective:To investigate changes in body ownership and chronic neuropathic pain in patients with spinal cord injury (SCI) using multisensory own body illusions and virtual reality (VR).Methods:Twenty patients with SCI with paraplegia and 20 healthy control participants (HC) participated in 2 factorial, randomized, repeated-measures design studies. In the virtual leg illusion (VLI), we applied asynchronous or synchronous visuotactile stimulation to the participant's back (either immediately above the lesion level or at the shoulder) and to the virtual legs as seen on a VR head-mounted display. We tested the effect of the VLI on the sense of leg ownership (questionnaires) and on perceived neuropathic pain (visual analogue scale pain ratings). We compared illusory leg ownership with illusory global body ownership (induced in the full body illusion [FBI]), by applying asynchronous or synchronous visuotactile stimulation to the participant's back and the back of a virtual body as seen on a head-mounted display.Results:Our data show that patients with SCI are less sensitive to multisensory stimulations inducing illusory leg ownership (as compared to HC) and that leg ownership decreased with time since SCI. In contrast, we found no differences between groups in global body ownership as tested in the FBI. VLI and FBI were both associated with mild analgesia that was only during the VLI specific for synchronous visuotactile stimulation and the lower back position.Conclusions:The present findings show that VR exposure using multisensory stimulation differently affected leg vs body ownership, and is associated with mild analgesia with potential for SCI neurorehabilitation protocols.
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Tsakiris, Manos, Ana Tajadura Jiménez, and Marcello Costantini. "Just a heartbeat away from one's body: interoceptive sensitivity predicts malleability of body-representations." Proceedings of the Royal Society B: Biological Sciences 278, no. 1717 (January 5, 2011): 2470–76. http://dx.doi.org/10.1098/rspb.2010.2547.
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Body-awareness relies on the representation of both interoceptive and exteroceptive percepts coming from one's body. However, the exact relationship and possible interaction of interoceptive and exteroceptive systems for body-awareness remain unknown. We sought to understand for the first time, to our knowledge, the interaction between interoceptive and exteroceptive awareness of the body. First, we measured interoceptive awareness with an established heartbeat monitoring task. We, then, used a multi-sensory-induced manipulation of body-ownership (e.g. Rubber Hand Illusion (RHI)) and we quantified the extent to which participants experienced ownership over a foreign body-part using behavioural, physiological and introspective measures. The results suggest that interoceptive sensitivity predicts the malleability of body representations, that is, people with low interoceptive sensitivity experienced a stronger illusion of ownership in the RHI. Importantly, this effect was not simply owing to a poor proprioceptive representation or differences in autonomic states of one's body prior to the multi-sensory stimulation, suggesting that interoceptive awareness modulates the online integration of multi-sensory body-percepts.
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Lenggenhager, Bigna, Leonie Hilti, and Peter Brugger. "Disturbed body integrity and the “rubber foot illusion”." Neuropsychology 29, no. 2 (March 2015): 205–11. http://dx.doi.org/10.1037/neu0000143.
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Raudsepp. "Visual Horizontal-Vertical Illusion: a body sway account?" Acta Physiologica Scandinavica 167, no. 2 (October 1999): 181 A20–181 A21. http://dx.doi.org/10.1046/j.1365-201x.1999.0600z.x.
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Kaneko, Fuminari. "Own-body Kinesthetic Illusion in the Augmented Reality." Japanese Journal of Rehabilitation Medicine 53, no. 3 (2016): 234–40. http://dx.doi.org/10.2490/jjrmc.53.234.
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Glasgow, Philip, and Stephen Mutch. "Mind, body and medicine: the illusion of separation." British Journal of Sports Medicine 52, no. 15 (July 17, 2018): 947. http://dx.doi.org/10.1136/bjsports-2018-099702.
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Bayer, Manuel, Sophie Betka, Bruno Herbelin, Olaf Blanke, and Eckart Zimmermann. "The full-body illusion changes visual depth perception." Journal of Vision 22, no. 14 (December 5, 2022): 3581. http://dx.doi.org/10.1167/jov.22.14.3581.
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Pavani, Francesco, and Massimiliano Zampini. "The Role of Hand Size in the Fake-Hand Illusion Paradigm." Perception 36, no. 10 (October 2007): 1547–54. http://dx.doi.org/10.1068/p5853.
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When a hand (either real or fake) is stimulated in synchrony with our own hand concealed from view, the felt position of our own hand can be biased toward the location of the seen hand. This intriguing phenomenon relies on the brain's ability to detect statistical correlations in the multisensory inputs (ie visual, tactile, and proprioceptive), but it is also modulated by the pre-existing representation of one's own body. Nonetheless, researchers appear to have accepted the assumption that the size of the seen hand does not matter for this illusion to occur. Here we used a real-time video image of the participant's own hand to elicit the illusion, but we varied the hand size in the video image so that the seen hand was either reduced, veridical, or enlarged in comparison to the participant's own hand. The results showed that visible-hand size modulated the illusion, which was present for veridical and enlarged images of the hand, but absent when the visible hand was reduced. These findings indicate that very specific aspects of our own body image (ie hand size) can constrain the multisensory modulation of the body schema highlighted by the fake-hand illusion paradigm. In addition, they suggest an asymmetric tendency to acknowledge enlarged (but not reduced) images of body parts within our body representation.
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Mundhenke, Florian. "Body Epistemes." Interactive Film & Media Journal 2, no. 4 (December 30, 2022): 114–21. http://dx.doi.org/10.32920/ifmj.v2i4.1689.
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This research concerns the relationships among space, story, and body in nonfictional Virtual Reality (VR) projects with the user as a first-person protagonist. What was once called immersive journalism (i.e., attempting to offer users physical experiences of factual journalism) has become increasingly film-oriented over the last five years with the further development of head-mounted displays for the consumer market. As such, projects often tell stories that relate to reality and allow protagonists to enter realistic narratives. Mel Slater has investigated VR projects since 2005, analyzing factors such as place illusion (PI) and plausibility illusion (Psi). In later writings, Slater expanded his research to include the body-oriented sense of embodiment (SoE) (Slater 2009; Slater et al. 2010; De La Pena et al. 2010; Kilteni et al. 2012). Since nonfictional VR mostly tells a story in the direction of the users, incorporating them into the story design, the effects of narration also should be considered. Domenic Arsénault (2005) noted three levels of narrative immersion in VR when dealing with narrative projects. Considering this, it is possible to develop a four-level matrix including place, plausibility, body perception, and narration. Starting in 2020, a Graduate student research project at the University of Leipzig was set up using this matrix to analyse four current examples for a small, non-representative study of twenty-four participants. Our findings demonstrate that space and story in first-person VR experiences are very important, while the installation of plausibility and coherence is less significant. The connecting factor of these two levels is one's own body. Users read, experience, and understand projects with their senses, perceptions, and cognition, making a discussion of an episteme of the body possible. Thus, stories from real life are not conveyed indirectly but experienced directly and personally.
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Guterstam, Arvid, Dennis E. O. Larsson, Joanna Szczotka, and H. Henrik Ehrsson. "Duplication of the bodily self: a perceptual illusion of dual full-body ownership and dual self-location." Royal Society Open Science 7, no. 12 (December 2020): 201911. http://dx.doi.org/10.1098/rsos.201911.
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Previous research has shown that it is possible to use multisensory stimulation to induce the perceptual illusion of owning supernumerary limbs, such as two right arms. However, it remains unclear whether the coherent feeling of owning a full-body may be duplicated in the same manner and whether such a dual full-body illusion could be used to split the unitary sense of self-location into two. Here, we examined whether healthy human participants can experience simultaneous ownership of two full-bodies, located either close in parallel or in two separate spatial locations. A previously described full-body illusion, based on visuo-tactile stimulation of an artificial body viewed from the first-person perspective (1PP) via head-mounted displays, was adapted to a dual-body setting and quantified in five experiments using questionnaires, a behavioural self-location task and threat-evoked skin conductance responses. The results of experiments 1–3 showed that synchronous visuo-tactile stimulation of two bodies viewed from the 1PP lying in parallel next to each other induced a significant illusion of dual full-body ownership. In experiment 4, we failed to find support for our working hypothesis that splitting the visual scene into two, so that each of the two illusory bodies was placed in distinct spatial environments, would lead to dual self-location. In a final exploratory experiment (no. 5), we found preliminary support for an illusion of dual self-location and dual body ownership by using dynamic changes between the 1PPs of two artificial bodies and/or a common third-person perspective in the ceiling of the testing room. These findings suggest that healthy people, under certain conditions of multisensory perceptual ambiguity, may experience dual body ownership and dual self-location. These findings suggest that the coherent sense of the bodily self located at a single place in space is the result of an active and dynamic perceptual integration process.
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Rubo, Marius, and Matthias Gamer. "Visuo-tactile congruency influences the body schema during full body ownership illusion." Consciousness and Cognition 73 (August 2019): 102758. http://dx.doi.org/10.1016/j.concog.2019.05.006.
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Giannopoulos, Anastasios E., Ioanna Zioga, Konstantinos Kontoangelos, Panos Papageorgiou, Fotini Kapsali, Christos N. Capsalis, and Charalabos Papageorgiou. "Deciding on Optical Illusions: Reduced Alpha Power in Body Dysmorphic Disorder." Brain Sciences 12, no. 2 (February 21, 2022): 293. http://dx.doi.org/10.3390/brainsci12020293.
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Background: Body dysmorphic disorder (BDD) is a psychiatric disorder characterized by excessive preoccupation with imagined defects in appearance. Optical illusions induce illusory effects that distort the presented stimulus, thus leading to ambiguous percepts. Using electroencephalography (EEG), we investigated whether BDD is related to differentiated perception during illusory percepts. Methods: A total of 18 BDD patients and 18 controls were presented with 39 optical illusions together with a statement testing whether or not they perceived the illusion. After a delay period, they were prompted to answer whether the statement was right/wrong and their degree of confidence in their answer. We investigated differences of BDD patients on task performance and self-reported confidence and analyzed the brain oscillations during decision-making using nonparametric cluster statistics. Results: Behaviorally, the BDD group exhibited reduced confidence when responding incorrectly, potentially attributed to higher levels of doubt. Electrophysiologically, the BDD group showed significantly reduced alpha power at the fronto-central and parietal scalp areas, suggesting impaired allocation of attention. Interestingly, the lower the alpha power of the identified cluster, the higher the BDD severity, as assessed by BDD psychometrics. Conclusions: Results evidenced that alpha power during illusory processing might serve as a quantitative EEG biomarker of BDD, potentially associated with reduced inhibition of task-irrelevant areas.