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Payne B, Catmur C. Embodiment in the enfacement illusion is mediated by self-other overlap. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230146. [PMID: 39155718 PMCID: PMC11391314 DOI: 10.1098/rstb.2023.0146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 02/20/2024] [Accepted: 03/04/2024] [Indexed: 08/20/2024] Open
Abstract
The enfacement illusion is a facial version of the rubber hand illusion, in which participants experience tactile stimulation of their own faces synchronously with the observation of the same stimulation applied to another's face. In previous studies, participants have reported experiencing an illusory embodiment of the other's face following synchronous compared to asynchronous stimulation. In a series of three experiments, we addressed the following three questions: (i) how does similarity between the self and the other, operationalized here as being of the same or different gender to the other, impact the experience of embodiment in the enfacement illusion; (ii) does the experience of embodiment result from alterations to the self-concept; and (iii) is susceptibility to the experience of embodiment associated with interoceptive processing, i.e. perception of the internal state of the body? Results indicate that embodiment is facilitated by the similarity between the self and the other and is mediated by the incorporation of the other into the self-concept, but sensitivity to one's own internal states does not impact upon embodiment within the enfacement illusion. This article is part of the theme issue 'Minds in movement: embodied cognition in the age of artificial intelligence'.
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Affiliation(s)
- Bryony Payne
- Department of Psychology, King's College London , London SE1 1UL, UK
| | - Caroline Catmur
- Department of Psychology, King's College London , London SE1 1UL, UK
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2
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Brouwer D, Morrin H, Nicholson TR, Terhune DB, Schrijnemaekers M, Edwards MJ, Gelauff J, Shotbolt P. Virtual reality in functional neurological disorder: a theoretical framework and research agenda for use in the real world. BMJ Neurol Open 2024; 6:e000622. [PMID: 38979395 PMCID: PMC11227774 DOI: 10.1136/bmjno-2023-000622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 04/01/2024] [Indexed: 07/10/2024] Open
Abstract
Functional neurological disorder (FND) is a common and disabling condition at the intersection of neurology and psychiatry. Despite remarkable progress over recent decades, the mechanisms of FND are still poorly understood and there are limited diagnostic tools and effective treatments. One potentially promising treatment modality for FND is virtual reality (VR), which has been increasingly applied to a broad range of conditions, including neuropsychiatric disorders. FND has unique features, many of which suggest the particular relevance for, and potential efficacy of, VR in both better understanding and managing the disorder. In this review, we describe how VR might be leveraged in the treatment and diagnosis of FND (with a primary focus on motor FND and persistent perceptual-postural dizziness given their prominence in the literature), as well as the elucidation of neurocognitive mechanisms and symptom phenomenology. First, we review what has been published to date on the applications of VR in FND and related neuropsychiatric disorders. We then discuss the hypothesised mechanism(s) underlying FND, focusing on the features that are most relevant to VR applications. Finally, we discuss the potential of VR in (1) advancing mechanistic understanding, focusing specifically on sense of agency, attention and suggestibility, (2) overcoming diagnostic challenges and (3) developing novel treatment modalities. This review aims to develop a theoretical foundation and research agenda for the use of VR in FND that might be applicable or adaptable to other related disorders.
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Affiliation(s)
- David Brouwer
- Department of Neurology, Amsterdam UMC Location AMC, Amsterdam, The Netherlands
| | - Hamilton Morrin
- Neuropsychiatry Research and Education Group, King's College London Institute of Psychiatry, Psychology & Neuroscience, London, UK
- South London and Maudsley NHS Foundation Trust, London, UK
| | - Timothy R Nicholson
- Neuropsychiatry Research and Education Group, King's College London Institute of Psychiatry, Psychology & Neuroscience, London, UK
- South London and Maudsley NHS Foundation Trust, London, UK
| | - Devin B Terhune
- Neuropsychiatry Research and Education Group, King's College London Institute of Psychiatry, Psychology & Neuroscience, London, UK
- Department of Psychology, King's College London Institute of Psychiatry, Psychology & Neuroscience, London, UK
| | | | - Mark J Edwards
- Neuropsychiatry Research and Education Group, King's College London Institute of Psychiatry, Psychology & Neuroscience, London, UK
- South London and Maudsley NHS Foundation Trust, London, UK
| | - Jeannette Gelauff
- Department of Neurology, Amsterdam UMC Location AMC, Amsterdam, The Netherlands
| | - Paul Shotbolt
- Neuropsychiatry Research and Education Group, King's College London Institute of Psychiatry, Psychology & Neuroscience, London, UK
- South London and Maudsley NHS Foundation Trust, London, UK
- Department of Psychological Medicine, King's College London Institute of Psychiatry, Psychology & Neuroscience, London, UK
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3
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O'Kane SH, Chancel M, Ehrsson HH. Hierarchical and dynamic relationships between body part ownership and full-body ownership. Cognition 2024; 246:105697. [PMID: 38364444 DOI: 10.1016/j.cognition.2023.105697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 12/12/2023] [Accepted: 12/13/2023] [Indexed: 02/18/2024]
Abstract
What is the relationship between experiencing individual body parts and the whole body as one's own? We theorised that body part ownership is driven primarily by the perceptual binding of visual and somatosensory signals from specific body parts, whereas full-body ownership depends on a more global binding process based on multisensory information from several body segments. To examine this hypothesis, we used a bodily illusion and asked participants to rate illusory changes in ownership over five different parts of a mannequin's body and the mannequin as a whole, while we manipulated the synchrony or asynchrony of visual and tactile stimuli delivered to three different body parts. We found that body part ownership was driven primarily by local visuotactile synchrony and could be experienced relatively independently of full-body ownership. Full-body ownership depended on the number of synchronously stimulated parts in a nonlinear manner, with the strongest full-body ownership illusion occurring when all parts received synchronous stimulation. Additionally, full-body ownership influenced body part ownership for nonstimulated body parts, and skin conductance responses provided physiological evidence supporting an interaction between body part and full-body ownership. We conclude that body part and full-body ownership correspond to different processes and propose a hierarchical probabilistic model to explain the relationship between part and whole in the context of multisensory awareness of one's own body.
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Affiliation(s)
- Sophie H O'Kane
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| | - Marie Chancel
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden; Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, LPNC, 38000 Grenoble, France
| | - H Henrik Ehrsson
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
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Sun Y, Zhu R, Hommel B, Ma K. Social exclusion in a virtual Cyberball game reduces the virtual hand illusion. Psychon Bull Rev 2024:10.3758/s13423-024-02456-w. [PMID: 38565842 DOI: 10.3758/s13423-024-02456-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/08/2024] [Indexed: 04/04/2024]
Abstract
Sense of ownership and agency are two important aspects of the minimal self, but how self-perception is affected by social conditions remains unclear. Here, we studied how social inclusion or exclusion of participants in the course of a virtual Cyberball game would affect explicit judgments and implicit measures of ownership and agency (proprioceptive drift, skin conductance responses, and intentional binding, respectively) in a virtual hand illusion paradigm, in which a virtual hand moved in or out of sync with the participants' own hand. Results show that synchrony affected all four measures. More importantly, this effect interacted with social inclusion/exclusion in the Cyberball game for both ownership and agency measure, showing that social exclusion reduces perceived agency and ownership.
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Affiliation(s)
- Yingbing Sun
- Key Laboratory of Personality and Cognition, Faculty of Psychological Science, Southwest University, Beibei, Chongqing, China
| | - Ruiyu Zhu
- Key Laboratory of Personality and Cognition, Faculty of Psychological Science, Southwest University, Beibei, Chongqing, China
| | - Bernhard Hommel
- Department of Psychology, Shandong Normal University, Jinan, China.
- Faculty of Psychology & University Neuropsychology Center, Faculty of Medicine, Cognitive Neurophysiology, TU Dresden, Dresden, Germany.
| | - Ke Ma
- Key Laboratory of Personality and Cognition, Faculty of Psychological Science, Southwest University, Beibei, Chongqing, China.
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5
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Dwivedi A, Yu S, Hao C, Salvietti G, Prattichizzo D, Beckerle P. How Positioning Wearable Haptic Interfaces on Limbs Influences Virtual Embodiment. IEEE TRANSACTIONS ON HAPTICS 2024; 17:292-301. [PMID: 38157458 DOI: 10.1109/toh.2023.3347351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
With increasing use of computer applications and robotic devices in our everyday life, and with the advent of metaverse, there is an urgent need of developing new types of interfaces that facilitate a more intuitive interaction in physical and virtual space. In this work, we investigate the influence of the location of haptic feedback devices on embodiment of virtual hands and user load during an interactive pick-and-place task. To do this, we conducted a user study with a 3x2 repeated measure experiment design: feedback position is varied between the distal phalanx of the index finger and the thumb, the proximal phalanx of the index finger and the thumb, and the wrist. These conditions of feedback are tested with the stimuli applied synchronously to the participant in one case, and with an additional delay of 350 ms in the second case. The results show that the location of the haptic feedback device does not affect embodiment, whereas the delay, i.e., whether the feedback is applied synchronously or asynchronously, affects embodiment. This suggests that for pick-and-place tasks, haptic feedback devices can be placed on the user's wrist without compromising performance making the hands to remain free, allowing unobstructed hand visibility for precise motion tracking, thereby improving accuracy.
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6
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Parrotta E, Bach P, Perrucci MG, Costantini M, Ferri F. Heart is deceitful above all things: Threat expectancy induces the illusory perception of increased heartrate. Cognition 2024; 245:105719. [PMID: 38278039 DOI: 10.1016/j.cognition.2024.105719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 11/24/2023] [Accepted: 01/08/2024] [Indexed: 01/28/2024]
Abstract
It has been suggested that our perception of the internal milieu, or the body's internal state, is shaped by our beliefs and previous knowledge about the body's expected state, rather than being solely based on actual interoceptive experiences. This study investigated whether heartbeat perception could be illusorily distorted towards prior subjective beliefs, such that threat expectations suffice to induce a misperception of heartbeat frequency. Participants were instructed to focus on their cardiac activity and report their heartbeat, either tapping along to it (Experiment 1) or silently counting (Experiment 2) while ECG was recorded. While completing this task, different cues provided valid predictive information about the intensity of an upcoming cutaneous stimulation (high- vs. low- pain). Results showed that participants expected a heart rate increase over the anticipation of high- vs. low-pain stimuli and that this belief was perceptually instantiated, as suggested by their interoceptive reports. Importantly, the perceived increase was not mirrored by the real heart rate. Perceptual modulations were absent when participants executed the same task but with an exteroceptive stimulus (Experiment 3). The findings reveal, for the first time, an interoceptive illusion of increased heartbeats elicited by threat expectancy and shed new light on interoceptive processes through the lenses of Bayesian predictive processes, providing tantalizing insights into how such illusory phenomena may intersect with the recognition and regulation of people's internal states.
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Affiliation(s)
- Eleonora Parrotta
- School of Psychology, University of Aberdeen, UK; School of Psychology, University of Plymouth, UK.
| | - Patric Bach
- School of Psychology, University of Aberdeen, UK; School of Psychology, University of Plymouth, UK
| | - Mauro Gianni Perrucci
- Department of Neuroscience, Imaging and Clinical Sciences, "G. d'Annunzio" University of Chieti-Pescara, Chieti, Italy; Institute for Advanced Biomedical Technologies - ITAB, "G. d'Annunzio" University of Chieti-Pescara, Chieti, Italy
| | - Marcello Costantini
- Department of Psychological, Health and Territorial Sciences, "G. d'Annunzio" University of Chieti-Pescara, Chieti, Italy; Institute for Advanced Biomedical Technologies - ITAB, "G. d'Annunzio" University of Chieti-Pescara, Chieti, Italy
| | - Francesca Ferri
- Department of Neuroscience, Imaging and Clinical Sciences, "G. d'Annunzio" University of Chieti-Pescara, Chieti, Italy; Institute for Advanced Biomedical Technologies - ITAB, "G. d'Annunzio" University of Chieti-Pescara, Chieti, Italy
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7
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Lanfranco RC, Chancel M, Ehrsson HH. Texture congruence modulates perceptual bias but not sensitivity to visuotactile stimulation during the rubber hand illusion. COGNITIVE, AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2024; 24:100-110. [PMID: 38263367 PMCID: PMC10827897 DOI: 10.3758/s13415-024-01155-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 01/02/2024] [Indexed: 01/25/2024]
Abstract
The sense of body ownership is the feeling that one's body belongs to oneself. To study body ownership, researchers use bodily illusions, such as the rubber hand illusion (RHI), which involves experiencing a visible rubber hand as part of one's body when the rubber hand is stroked simultaneously with the hidden real hand. The RHI is based on a combination of vision, touch, and proprioceptive information following the principles of multisensory integration. It has been posited that texture incongruence between rubber hand and real hand weakens the RHI, but the underlying mechanisms remain poorly understood. To investigate this, we recently developed a novel psychophysical RHI paradigm. Based on fitting psychometric functions, we discovered the RHI resulted in shifts in the point of subjective equality when the rubber hand and the real hand were stroked with matching materials. We analysed these datasets further by using signal detection theory analysis, which distinguishes between the participants' sensitivity to visuotactile stimulation and the associated perceptual bias. We found that texture incongruence influences the RHI's perceptual bias but not its sensitivity to visuotactile stimulation. We observed that the texture congruence bias effect was the strongest in shorter visuotactile asynchronies (50-100 ms) and weaker in longer asynchronies (200 ms). These results suggest texture-related perceptual bias is most prominent when the illusion's sensitivity is at its lowest. Our findings shed light on the intricate interactions between top-down and bottom-up processes in body ownership, the links between body ownership and multisensory integration, and the impact of texture congruence on the RHI.
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Affiliation(s)
- Renzo C Lanfranco
- Department of Neuroscience, Karolinska Institutet, Solnavägen 9, 171 65, Stockholm, Sweden.
| | - Marie Chancel
- Department of Neuroscience, Karolinska Institutet, Solnavägen 9, 171 65, Stockholm, Sweden
- Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, LPNC, 38000, Grenoble, France
| | - H Henrik Ehrsson
- Department of Neuroscience, Karolinska Institutet, Solnavägen 9, 171 65, Stockholm, Sweden.
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8
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Tosi G, Mentesana B, Romano D. The correlation between proprioceptive drift and subjective embodiment during the rubber hand illusion: A meta-analytic approach. Q J Exp Psychol (Hove) 2023; 76:2197-2207. [PMID: 36880657 DOI: 10.1177/17470218231156849] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
Abstract
In the rubber hand illusion (RHI), participants see a fake hand touched synchronously with their real hand, which is hidden from view. The three-way interaction between vision, touch, and proprioception induces the sensation that the dummy hand belongs to oneself (i.e., subjective embodiment) and the illusory displacement of the real hand towards the fake one (i.e., proprioceptive drift). In the literature, there are mixed results (some positive and some null) regarding the existence of a relationship between subjective embodiment and proprioceptive drift. We conducted a Bayesian meta-analysis to tackle this issue quantitatively. Evidence strongly favours the presence of a correlation between subjective embodiment and proprioceptive drift, supporting the model proposed by Botvinick and Cohen in 1998. However, the correlation is around .35, a value suggesting that the two indices capture different facets of the RHI. This result clarifies the association between the illusory effects produced by the RHI and may be helpful for designing studies having appropriate statistical power.
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Affiliation(s)
- Giorgia Tosi
- Department of History, Society and Human Studies, University of Salento, Lecce, Italy
| | | | - Daniele Romano
- Department of History, Society and Human Studies, University of Salento, Lecce, Italy
- Department of Psychology, University of Milano-Bicocca, Milan, Italy
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9
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Pilacinski A, Metzler M, Klaes C. Phantom touch illusion, an unexpected phenomenological effect of tactile gating in the absence of tactile stimulation. Sci Rep 2023; 13:15453. [PMID: 37723256 PMCID: PMC10507094 DOI: 10.1038/s41598-023-42683-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 09/13/2023] [Indexed: 09/20/2023] Open
Abstract
We report the presence of a tingling sensation perceived during self-touch without physical stimulation. We used immersive virtual reality scenarios in which subjects touched their body using a virtual object. This touch resulted in a tingling sensation corresponding to the location touched on the virtual body. We called it "phantom touch illusion" (PTI). Interestingly, the illusion was also reported when subjects touched invisible (inferred) parts of their limb. We reason that this PTI results from tactile gating process during self-touch if there is no tactile input to supress. The reported PTI when touching invisible body parts indicates that tactile gating is not exclusively based on vision, but rather on multi-sensory, top-down input involving body schema. This supplementary finding shows that representations of one's own body are defined top-down, beyond the available sensory information.
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Affiliation(s)
- Artur Pilacinski
- Chair for Neurotechnology, Ruhr-University Bochum, Bochum, Germany.
| | - Marita Metzler
- Chair for Neurotechnology, Ruhr-University Bochum, Bochum, Germany
| | - Christian Klaes
- Chair for Neurotechnology, Ruhr-University Bochum, Bochum, Germany
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10
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Apelian C, Terhune DB, De Vignemont F. Hypnotic suggestion versus sensory modulation of bodily awareness. PLoS One 2023; 18:e0291493. [PMID: 37699046 PMCID: PMC10497174 DOI: 10.1371/journal.pone.0291493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 08/30/2023] [Indexed: 09/14/2023] Open
Abstract
Bodily awareness arises from somatosensory, vestibular, and visual inputs but cannot be reduced to these incoming sensory signals. Cognitive factors are known to also impact bodily awareness, though their specific influence is poorly understood. Here we systematically compared the effects of sensory (bottom-up) and cognitive (top-down) manipulations on the estimated size of body parts. Toward this end, in a repeated-measures design, we sought to induce the illusion that the right index finger was elongating by vibrating the biceps tendon of the left arm whilst participants grasped the tip of their right index finger (Lackner illusion; bottom-up) and separately by hypnotic suggestion (top-down), with a sham version of the Lackner illusion as an active control condition. The effects of these manipulations were assessed with perceptual and motor tasks to capture different components of the representation of body size. We found that hypnotic suggestion significantly induced the illusion in both tasks relative to the sham condition. The magnitudes of these effects were stronger than those in the Lackner illusion condition, which only produced a significantly stronger illusion than the sham condition in the perceptual task. We further observed that illusion magnitude significantly correlated across tasks and conditions, suggesting partly shared mechanisms. These results are in line with theories of separate but interacting representational processes for perception and action and highlight the influence of cognitive factors on low-level body representations.
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Affiliation(s)
- C. Apelian
- Département d’études Cognitives, Institut Jean Nicod, ENS, EHESS, CNRS, PSL University, Paris, France
- ARCHE, Formation, Paris, France
| | - D. B. Terhune
- Department of Psychology, Goldsmiths, University of London, London, United Kingdom
- Department of Psychology, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, United Kingdom
| | - F. De Vignemont
- Département d’études Cognitives, Institut Jean Nicod, ENS, EHESS, CNRS, PSL University, Paris, France
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11
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Finotti G, Garofalo S, Costantini M, Proffitt DR. Temporal dynamics of the Rubber Hand Illusion. Sci Rep 2023; 13:7526. [PMID: 37160924 PMCID: PMC10170134 DOI: 10.1038/s41598-023-33747-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 04/18/2023] [Indexed: 05/11/2023] Open
Abstract
It is widely accepted that the representation of the body is not fixed and immutable, but rather flexible and constantly updated based on a continuous stream of multisensory information. This mechanism can be very useful to adapt to several situations, but it would not be adaptive if the body representation was too malleable or if it wasn't capable of restoring its integrity after a transient modification. Here we used the Rubber Hand Illusion (RHI) to investigate how quickly the body representation can be modified. Previous studies have investigated the timing of the onset and offset of the illusion, however, they did not assess a fine temporal resolution. Here, we used a potentiometer to record a moment-by-moment rating of the feeling of owning the RH for two minutes during the visuo-tactile stimulation and two minutes following the stimulation. Our results suggest that the feeling of Ownership is already established during the first 19 s of stimulation then it continues to grow, but at a much slower pace. The feeling of Ownership disappears within 66 s from the end of the stimulation. This work sheds new light on the temporal dynamics of the RHI and the malleability of the body self-consciousness.
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Affiliation(s)
- Gianluca Finotti
- Department of Psychology, University of Virginia, Charlottesville, Virginia, USA.
- Center for Studies and Research in Cognitive Neuroscience, Department of Psychology, University of Bologna, Via Rasi e Spinelli 176, 47521, Cesena, FC, Italy.
| | - Sara Garofalo
- Center for Studies and Research in Cognitive Neuroscience, Department of Psychology, University of Bologna, Via Rasi e Spinelli 176, 47521, Cesena, FC, Italy
| | - Marcello Costantini
- Department of Psychological, Health and Territorial Sciences, University G. d'Annunzio, Chieti-Pescara, Italy
| | - Dennis R Proffitt
- Department of Psychology, University of Virginia, Charlottesville, Virginia, USA
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12
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Berger CC, Coppi S, Ehrsson HH. Synchronous motor imagery and visual feedback of finger movement elicit the moving rubber hand illusion, at least in illusion-susceptible individuals. Exp Brain Res 2023; 241:1021-1039. [PMID: 36928694 PMCID: PMC10081980 DOI: 10.1007/s00221-023-06586-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 02/26/2023] [Indexed: 03/18/2023]
Abstract
Recent evidence suggests that imagined auditory and visual sensory stimuli can be integrated with real sensory information from a different sensory modality to change the perception of external events via cross-modal multisensory integration mechanisms. Here, we explored whether imagined voluntary movements can integrate visual and proprioceptive cues to change how we perceive our own limbs in space. Participants viewed a robotic hand wearing a glove repetitively moving its right index finger up and down at a frequency of 1 Hz, while they imagined executing the corresponding movements synchronously or asynchronously (kinesthetic-motor imagery); electromyography (EMG) from the participants' right index flexor muscle confirmed that the participants kept their hand relaxed while imagining the movements. The questionnaire results revealed that the synchronously imagined movements elicited illusory ownership and a sense of agency over the moving robotic hand-the moving rubber hand illusion-compared with asynchronously imagined movements; individuals who affirmed experiencing the illusion with real synchronous movement also did so with synchronous imagined movements. The results from a proprioceptive drift task further demonstrated a shift in the perceived location of the participants' real hand toward the robotic hand in the synchronous versus the asynchronous motor imagery condition. These results suggest that kinesthetic motor imagery can be used to replace veridical congruent somatosensory feedback from a moving finger in the moving rubber hand illusion to trigger illusory body ownership and agency, but only if the temporal congruence rule of the illusion is obeyed. This observation extends previous studies on the integration of mental imagery and sensory perception to the case of multisensory bodily awareness, which has potentially important implications for research into embodiment of brain-computer interface controlled robotic prostheses and computer-generated limbs in virtual reality.
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Affiliation(s)
- Christopher C Berger
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
- Division of Biology and Biological Engineering/Computation and Neural Systems, California Institute of Technology, Pasadena, CA, USA
| | - Sara Coppi
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| | - H Henrik Ehrsson
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
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13
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Suzuki K, Mariola A, Schwartzman DJ, Seth AK. Using Extended Reality to Study the Experience of Presence. Curr Top Behav Neurosci 2023; 65:255-285. [PMID: 36592275 DOI: 10.1007/7854_2022_401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Extended reality (XR), encompassing various forms of virtual reality (VR) and augmented reality (AR), has become a powerful experimental tool in consciousness research due to its capability to create holistic and immersive experiences of oneself and surrounding environments through simulation. One hallmark of a successful XR experience is when it elicits a strong sense of presence, which can be thought of as a subjective sense of reality of the self and the world. Although XR research has shed light on many factors that may influence presence (or its absence) in XR environments, there remains much to be discovered about the detailed and diverse phenomenology of presence, and the neurocognitive mechanisms that underlie it. In this chapter, we analyse the concept of presence and relate it to the way in which humans may generate and maintain a stable sense of reality during both natural perception and virtual experiences. We start by reviewing the concept of presence as developed in XR research, covering both factors that may influence presence and potential ways of measuring presence. We then discuss the phenomenological characteristics of presence in human consciousness, drawing on clinical examples where presence is disturbed. Next, we describe two experiments using XR that investigated the effects of sensorimotor contingency and affordances on a specific form of presence related to the sense of objects as really existing in the world, referred to as 'objecthood'. We then go beyond perceptual presence to discuss the concept of 'conviction about reality', which corresponds to people's beliefs about the reality status of their perceptual experiences. We finish by exploring how the novel XR method of 'Substitutional Reality' can allow experimental investigation of these topics, opening new experimental directions for studying presence beyond the 'as-if' experience of fully simulated environments.
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Affiliation(s)
- Keisuke Suzuki
- Center for Human Nature, Artificial Intelligence and Neuroscience (CHAIN), Hokkaido University, Sapporo, Hokkaido, Japan.
- Sackler Centre for Consciousness Science, School of Engineering and Informatics, University of Sussex, Brighton, UK.
| | - Alberto Mariola
- Sackler Centre for Consciousness Science, School of Engineering and Informatics, University of Sussex, Brighton, UK
- School of Engineering and Informatics, University of Sussex, Brighton, UK
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, UK
| | - David J Schwartzman
- Sackler Centre for Consciousness Science, School of Engineering and Informatics, University of Sussex, Brighton, UK
- School of Engineering and Informatics, University of Sussex, Brighton, UK
| | - Anil K Seth
- Sackler Centre for Consciousness Science, School of Engineering and Informatics, University of Sussex, Brighton, UK
- School of Engineering and Informatics, University of Sussex, Brighton, UK
- Program on Brain, Mind, and Consciousness, Canadian Institute for Advanced Research, Toronto, ON, Canada
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Segil JL, Roldan LM, Graczyk EL. Measuring embodiment: A review of methods for prosthetic devices. Front Neurorobot 2022; 16:902162. [PMID: 36590084 PMCID: PMC9797051 DOI: 10.3389/fnbot.2022.902162] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 10/25/2022] [Indexed: 12/23/2022] Open
Abstract
The development of neural interfaces to provide improved control and somatosensory feedback from prosthetic limbs has initiated a new ability to probe the various dimensions of embodiment. Scientists in the field of neuroprosthetics require dependable measures of ownership, body representation, and agency to quantify the sense of embodiment felt by patients for their prosthetic limbs. These measures are critical to perform generalizable experiments and compare the utility of the new technologies being developed. Here, we review outcome measures used in the literature to evaluate the senses of ownership, body-representation, and agency. We categorize these existing measures based on the fundamental psychometric property measured and whether it is a behavioral or physiological measure. We present arguments for the efficacy and pitfalls of each measure to guide better experimental designs and future outcome measure development. The purpose of this review is to aid prosthesis researchers and technology developers in understanding the concept of embodiment and selecting metrics to assess embodiment in their research. Advances in the ability to measure the embodiment of prosthetic devices have far-reaching implications in the improvement of prosthetic limbs as well as promoting a broader understanding of ourselves as embodied agents.
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Affiliation(s)
- Jacob L. Segil
- Department of Mechanical Engineering, University of Colorado, Boulder, CO, United States
- Rocky Mountain Regional VA Medical Center, Aurora, CO, United States
| | - Leah Marie Roldan
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
- Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States
| | - Emily L. Graczyk
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
- Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States
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15
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The role of hand size in body representation: a developmental investigation. Sci Rep 2022; 12:19281. [PMID: 36369342 PMCID: PMC9652309 DOI: 10.1038/s41598-022-23716-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 11/03/2022] [Indexed: 11/13/2022] Open
Abstract
Knowledge of one's own body size is a crucial facet of body representation, both for acting on the environment and perhaps also for constraining body ownership. However, representations of body size may be somewhat plastic, particularly to allow for physical growth in childhood. Here we report a developmental investigation into the role of hand size in body representation (the sense of body ownership, perception of hand position, and perception of own-hand size). Using the rubber hand illusion paradigm, this study used different fake hand sizes (60%, 80%, 100%, 120% or 140% of typical size) in three age groups (6- to 7-year-olds, 12- to 13-year-olds, and adults; N = 229). We found no evidence that hand size constrains ownership or position: participants embodied hands which were both larger and smaller than their own, and indeed judged their own hands to have changed size following the illusion. Children and adolescents embodied the fake hands more than adults, with a greater tendency to feel their own hand had changed size. Adolescents were particularly sensitive to multisensory information. In sum, we found substantial plasticity in the representation of own-body size, with partial support for the hypothesis that children have looser representations than adults.
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16
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Demand characteristics challenge effects in embodiment and presence. Sci Rep 2022; 12:14084. [PMID: 35982112 PMCID: PMC9387424 DOI: 10.1038/s41598-022-18160-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 08/05/2022] [Indexed: 11/17/2022] Open
Abstract
The sensations to own and control a body as well as being located in a body describe the relation between ourselves and our body, termed embodiment. Embodiment plays a central role in our everyday actions. However, its assessment is challenging. Recent findings suggest that measures on embodiment are confounded by demand characteristics and suggestibility. To investigate the impact of demand characteristics on embodiment and presence, we compared results from an online experiment measuring participants’ expectations, to the same experiment in virtual reality (VR). In the online experiment, participants watched a video of a participant performing the VR experiment. In the VR experiment, participants performed a soap-bubble-kicking task, which allowed the feelings of embodiment and presence to arise. We manipulated temporo-spatial movement synchrony (Movement: synchronous, asynchronous) and avatar visibility (Visibility: visible, invisible). In addition, we assessed participants’ suggestibility with exercises. The introduced manipulations influenced the ratings in both experiments similarly. Embodiment ratings were additionally affected by suggestibility. Altogether, our results show that participants were aware of the research hypotheses, which indicates that demand characteristics confound embodiment and presence research alike. Overcoming challenges of demand characteristics is crucial to correctly interpret scientific results and to translate these results into applied settings.
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17
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Sciortino P, Kayser C. The rubber hand illusion is accompanied by a distributed reduction of alpha and beta power in the EEG. PLoS One 2022; 17:e0271659. [PMID: 35905100 PMCID: PMC9337658 DOI: 10.1371/journal.pone.0271659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 07/05/2022] [Indexed: 11/18/2022] Open
Abstract
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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Affiliation(s)
- Placido Sciortino
- Department of Cognitive Neuroscience, Faculty of Biology, Bielefeld University, Bielefeld, Germany
- * E-mail:
| | - Christoph Kayser
- Department of Cognitive Neuroscience, Faculty of Biology, Bielefeld University, Bielefeld, Germany
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18
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Maselli A, Lanillos P, Pezzulo G. Active inference unifies intentional and conflict-resolution imperatives of motor control. PLoS Comput Biol 2022; 18:e1010095. [PMID: 35714105 PMCID: PMC9205531 DOI: 10.1371/journal.pcbi.1010095] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 04/11/2022] [Indexed: 11/19/2022] Open
Abstract
The field of motor control has long focused on the achievement of external goals through action (e.g., reaching and grasping objects). However, recent studies in conditions of multisensory conflict, such as when a subject experiences the rubber hand illusion or embodies an avatar in virtual reality, reveal the presence of unconscious movements that are not goal-directed, but rather aim at resolving multisensory conflicts; for example, by aligning the position of a person’s arm with that of an embodied avatar. This second, conflict-resolution imperative of movement control did not emerge in classical studies of motor adaptation and online corrections, which did not allow movements to reduce the conflicts; and has been largely ignored so far in formal theories. Here, we propose a model of movement control grounded in the theory of active inference that integrates intentional and conflict-resolution imperatives. We present three simulations showing that the active inference model is able to characterize movements guided by the intention to achieve an external goal, by the necessity to resolve multisensory conflict, or both. Furthermore, our simulations reveal a fundamental difference between the (active) inference underlying intentional and conflict-resolution imperatives by showing that it is driven by two different (model and sensory) kinds of prediction errors. Finally, our simulations show that when movement is only guided by conflict resolution, the model incorrectly infers that is velocity is zero, as if it was not moving. This result suggests a novel speculative explanation for the fact that people are unaware of their subtle compensatory movements to avoid multisensory conflict. Furthermore, it can potentially help shed light on deficits of motor awareness that arise in psychopathological conditions.
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Affiliation(s)
- Antonella Maselli
- Institute of Cognitive Sciences and Technology, National Research Council (CNR), Rome, Italy
| | - Pablo Lanillos
- Donders Institute for Brain, Cognition and Behaviour, Artificial Intelligence Department, Radboud University, Nijmegen, The Netherlands
| | - Giovanni Pezzulo
- Institute of Cognitive Sciences and Technology, National Research Council (CNR), Rome, Italy
- * E-mail:
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19
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Slater M, Ehrsson HH. Multisensory Integration Dominates Hypnotisability and Expectations in the Rubber Hand Illusion. Front Hum Neurosci 2022; 16:834492. [PMID: 35782045 PMCID: PMC9244625 DOI: 10.3389/fnhum.2022.834492] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 05/04/2022] [Indexed: 12/02/2022] Open
Abstract
Some recent papers by P. Lush and colleagues have argued that the rubber hand illusion (RHI), where participants can feel a rubber hand as their own under appropriate multisensory stimulation, may be caused mainly by hypnotic suggestibility and expectations (demand characteristics). These papers rely primarily on a study with 353 participants who took part in a RHI experiment carried out in a classical way with brush stroking. Participants experienced a synchronous condition where the rubber hand was seen to be touched in synchrony with touch felt on their corresponding hidden real hand, or the touches were applied asynchronously as a control. Each participant had a related measure of their hypnotisability on a scale known as the Sussex-Waterloo Scale of Hypnotisability (SWASH). The authors found a correlation between the questionnaire ratings of the RHI in the synchronous condition and the SWASH score. From this, they concluded that the RHI is largely driven by suggestibility and further proposed that suggestibility and expectations may even entirely explain the RHI. Here we examine their claims in a series of extensive new analyses of their data. We find that at every level of SWASH, the synchronous stimulation results in greater levels of the illusion than the asynchronous condition; moreover, proprioceptive drift is greater in the synchronous case at every level of SWASH. Thus, while the level of hypnotisability does modestly influence the subjective reports (higher SWASH is associated with somewhat higher illusion ratings), the major difference between the synchronous and asynchronous stimulation is always present. Furthermore, by including in the model the participants' expectancy ratings of how strongly they initially believed they would experience the RHI in the two conditions, we show that expectations had a very small effect on the illusion ratings; model comparisons further demonstrate that the multisensory condition is two-to-three-times as dominant as the other factors, with hypnotisability contributing modestly and expectations negligibly. Thus, although the results indicate that trait suggestibility may modulate the RHI, presumably through intersubject variations in top-down factors, the findings also suggest that the primary explanation for the RHI is as a multisensory bodily illusion.
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Affiliation(s)
- Mel Slater
- Event Lab, Department of Clinical Psychology and Psychobiology, University of Barcelona, Barcelona, Spain
- Institute of Neurosciences of the University of Barcelona, Barcelona, Spain
| | - H. Henrik Ehrsson
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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20
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Hsu TY, Zhou JF, Yeh SL, Northoff G, Lane TJ. Intrinsic neural activity predisposes susceptibility to a body illusion. Cereb Cortex Commun 2022; 3:tgac012. [PMID: 35382092 PMCID: PMC8976633 DOI: 10.1093/texcom/tgac012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 02/21/2022] [Accepted: 03/01/2022] [Indexed: 11/13/2022] Open
Abstract
Susceptibility to the rubber hand illusion (RHI) varies. To date, however, there is no consensus explanation of this variability. Previous studies, focused on the role of multisensory integration, have searched for neural correlates of the illusion. But those studies have failed to identify a sufficient set of functionally specific neural correlates. Because some evidence suggests that frontal α power is one means of tracking neural instantiations of self, we hypothesized that the higher the frontal α power during the eyes-closed resting state, the more stable the self. As a corollary, we infer that the more stable the self, the less susceptible are participants to a blurring of boundaries—to feeling that the rubber hand belongs to them. Indeed, we found that frontal α amplitude oscillations negatively correlate with susceptibility. Moreover, since lower frequencies often modulate higher frequencies, we explored the possibility that this might be the case for the RHI. Indeed, some evidence suggests that high frontal α power observed in low-RHI participants is modulated by δ frequency oscillations. We conclude that while neural correlates of multisensory integration might be necessary for the RHI, sufficient explanation involves variable intrinsic neural activity that modulates how the brain responds to incompatible sensory stimuli.
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Affiliation(s)
- Tzu-Yu Hsu
- Graduate Institute of Mind, Brain, and Consciousness, Taipei Medical University, Taipei, Taiwan
- Brain and Consciousness Research Centre, TMU Shuang Ho Hospital, New Taipei City, Taiwan
| | - Ji-Fan Zhou
- Department of Psychology and Behavioral Sciences, Zhejiang University, Hang Zhou, China
| | - Su-Ling Yeh
- Department of Psychology, National Taiwan University, Taipei, Taiwan
- Graduate Institute of Brain and Mind Sciences, National Taiwan University, Taipei, Taiwan
- Neurobiology and Cognitive Neuroscience Center, National Taiwan University, Taipei, Taiwan
- Center for Artificial Intelligence and Advanced Robotics, National Taiwan University, Taipei, Taiwan
| | - Georg Northoff
- Institute of Mental Health Research, University of Ottawa, Ottawa, Canada
| | - Timothy Joseph Lane
- Graduate Institute of Mind, Brain, and Consciousness, Taipei Medical University, Taipei, Taiwan
- Brain and Consciousness Research Centre, TMU Shuang Ho Hospital, New Taipei City, Taiwan
- Institute of European and American Studies, Academia Sinica, Taipei, Taiwan
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