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1
Preuss Mattsson, Nora, Sara Coppi, Marie Chancel, and H. Henrik Ehrsson. "Combination of visuo-tactile and visuo-vestibular correlations in illusory body ownership and self-motion sensations." PLOS ONE 17, no. 11 (November 15, 2022): e0277080. http://dx.doi.org/10.1371/journal.pone.0277080.
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Previous studies have shown that illusory ownership over a mannequin’s body can be induced through synchronous visuo-tactile stimulation as well as through synchronous visuo-vestibular stimulation. The current study aimed to elucidate how three-way combinations of correlated visual, tactile and vestibular signals contribute to the senses of body ownership and self-motion. Visuo-tactile temporal congruence was manipulated by touching the mannequin’s body and the participant’s unseen real body on the trunk with a small object either synchronously or asynchronously. Visuo-vestibular temporal congruence was manipulated by synchronous or asynchronous presentation of a visual motion cue (the background rotating around the mannequin in one direction) and galvanic stimulation of the vestibular nerve generating a rotation sensation (in the same direction). The illusory experiences were quantified using a questionnaire; threat-evoked skin-conductance responses (SCRs) provided complementary indirect physiological evidence for the illusion. Ratings on the illusion questionnaire statement showed significant main effects of synchronous visuo-vestibular and synchronous visuo-tactile stimulations, suggesting that both of these pairs of bimodal correlations contribute to the ownership illusion. Interestingly, visuo-tactile synchrony dominated because synchronous visuo-tactile stimulation combined with asynchronous visuo-vestibular stimulation elicited a body ownership illusion of similar strength as when both bimodal combinations were synchronous. Moreover, both visuo-tactile and visuo-vestibular synchrony were associated with enhanced self-motion perception; self-motion sensations were even triggered when visuo-tactile synchrony was combined with visuo-vestibular asynchrony, suggesting that ownership enhanced the relevance of visual information as a self-motion cue. Finally, the SCR results suggest that synchronous stimulation of either modality pair led to a stronger illusion compared to the asynchronous conditions. Collectively, the results suggest that visuo-tactile temporal correlations have a stronger influence on body ownership than visuo-vestibular correlations and that ownership boosts self-motion perception. We present a Bayesian causal inference model that can explain how visuo-vestibular and visuo-tactile information are combined in multisensory own-body perception.
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Martolini, Chiara, Giulia Cappagli, Sabrina Signorini, and Monica Gori. "Effects of Increasing Stimulated Area in Spatiotemporally Congruent Unisensory and Multisensory Conditions." Brain Sciences 11, no. 3 (March 9, 2021): 343. http://dx.doi.org/10.3390/brainsci11030343.
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Research has shown that the ability to integrate complementary sensory inputs into a unique and coherent percept based on spatiotemporal coincidence can improve perceptual precision, namely multisensory integration. Despite the extensive research on multisensory integration, very little is known about the principal mechanisms responsible for the spatial interaction of multiple sensory stimuli. Furthermore, it is not clear whether the size of spatialized stimulation can affect unisensory and multisensory perception. The present study aims to unravel whether the stimulated area’s increase has a detrimental or beneficial effect on sensory threshold. Sixteen typical adults were asked to discriminate unimodal (visual, auditory, tactile), bimodal (audio-visual, audio-tactile, visuo-tactile) and trimodal (audio-visual-tactile) stimulation produced by one, two, three or four devices positioned on the forearm. Results related to unisensory conditions indicate that the increase of the stimulated area has a detrimental effect on auditory and tactile accuracy and visual reaction times, suggesting that the size of stimulated areas affects these perceptual stimulations. Concerning multisensory stimulation, our findings indicate that integrating auditory and tactile information improves sensory precision only when the stimulation area is augmented to four devices, suggesting that multisensory interaction is occurring for expanded spatial areas.
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Roel Lesur, Marte, Helena Aicher, Sylvain Delplanque, and Bigna Lenggenhager. "Being Short, Sweet, and Sour: Congruent Visuo-Olfactory Stimulation Enhances Illusory Embodiment." Perception 49, no. 6 (June 2020): 693–96. http://dx.doi.org/10.1177/0301006620928669.
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Bodily self-identification has shown to be easily altered through spatiotemporally congruent multimodal signals. While such manipulations are mostly studied through visuo-tactile or visuo-motor stimulation, here we investigated whether congruent visuo-olfactory cues might enhance illusory self-identification with an arbitrary object. Using virtual reality, healthy individuals saw a grapefruit from its supposed first-person perspective that was touched in synchrony with their own body. The touch attempted to replicate what was seen as softly squeezing the grapefruit. Crucially, when we additionally presented the smell of a grapefruit in synchrony with the squeezing, they self-identified stronger with the fruit than when they smelled strawberry.
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Beck, Brianna, Caterina Bertini, and Elisabetta Ladavas. "Interpersonal multisensory stimulation and emotion: The impact of threat-indicative facial expressions on enfacement." Seeing and Perceiving 25 (2012): 97–98. http://dx.doi.org/10.1163/187847612x647306.
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Prior studies have identified an ‘enfacement effect’ in which participants incorporate another’s face into their self-face representation after observing that face touched repeatedly in synchrony with touch on their own face (Sforza et al., 2010; Tsakiris, 2008). The degree of self-face/other-face merging is positively correlated with participants’ trait-level empathy scores (Sforza et al., 2010) and affects judgments of the other’s personality (Paladino et al., 2010), suggesting that enfacement also modulates higher-order representations of ‘self’ and ‘other’ involved in social and emotional evaluations. To test this hypothesis, we varied not only whether visuo-tactile stimulation was synchronous or asynchronous but also whether the person being touched in the video displayed an emotional expression indicative of threat, either fear or anger. We hypothesized that participants would incorporate the faces of fearful others more than the faces of angry others after a shared visuo-tactile experience because of a potentially stronger representation of the sight of fear in somatosensory cortices compared to the sight of anger (Cardini et al., 2012). Instead, we found that the enfacement effect (i.e., greater self-face/other-face merging following synchronous compared to asynchronous visuo-tactile stimulation) was abolished if the other person displayed fear but remained if they expressed anger. This nonetheless suggests that enfacement operates on an evaluative self-representation as well as a physical one because the effect changes with the emotional content of the other’s face. Further research into the neural mechanism behind the enfacement effect is needed to determine why sight of fear diminishes it rather than enhancing it.
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Campus, C., L. Brayda, F. De Carli, R. Chellali, F. Famà, C. Bruzzo, L. Lucagrossi, and G. Rodriguez. "Tactile exploration of virtual objects for blind and sighted people: the role of beta 1 EEG band in sensory substitution and supramodal mental mapping." Journal of Neurophysiology 107, no. 10 (May 15, 2012): 2713–29. http://dx.doi.org/10.1152/jn.00624.2011.
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The neural correlates of exploration and cognitive mapping in blindness remain elusive. The role of visuo-spatial pathways in blind vs. sighted subjects is still under debate. In this preliminary study, we investigate, as a possible estimation of the activity in the visuo-spatial pathways, the EEG patterns of blind and blindfolded-sighted subjects during the active tactile construction of cognitive maps from virtual objects compared with rest and passive tactile stimulation. Ten blind and ten matched, blindfolded-sighted subjects participated in the study. Events were defined as moments when the finger was only stimulated (passive stimulation) or the contour of a virtual object was touched (during active exploration). Event-related spectral power and coherence perturbations were evaluated within the beta 1 band (14–18 Hz). They were then related to a subjective cognitive-load estimation required by the explorations [namely, perceived levels of difficulty (PLD)]. We found complementary cues for sensory substitution and spatial processing in both groups: both blind and sighted subjects showed, while exploring, late power decreases and early power increases, potentially associated with motor programming and touch, respectively. The latter involved occipital areas only for blind subjects (long-term plasticity) and only during active exploration, thus supporting tactile-to-visual sensory substitution. In both groups, coherences emerged among the fronto-central, centro-parietal, and occipito-temporal derivations associated with visuo-spatial processing. This seems in accordance with mental map construction involving spatial processing, sensory-motor processing, and working memory. The observed involvement of the occipital regions suggests that a substitution process also occurs in sighted subjects. Only during explorations did coherence correlate positively with PLD for both groups and in derivations, which can be related to visuo-spatial processing, supporting the existence of supramodal spatial processing independently of vision capabilities.
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Porras Garcia, Bruno, Marta Ferrer Garcia, Agata Olszewska, Lena Yilmaz, Cristina González Ibañez, Mireia Gracia Blanes, Gamze Gültekin, Eduardo Serrano Troncoso, and José Gutiérrez Maldonado. "Is This My Own Body? Changing the Perceptual and Affective Body Image Experience among College Students Using a New Virtual Reality Embodiment-Based Technique." Journal of Clinical Medicine 8, no. 7 (June 27, 2019): 925. http://dx.doi.org/10.3390/jcm8070925.
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Body image disturbances (BIDs) have been widely studied using virtual reality (VR) devices that induce a full body illusion (FBI) and allow manipulation of the individual’s perceptual and affective experiences of the body. This study aimed to assess whether the induction of the FBI over a virtual body would produce changes in body-related anxiety and BIDs using a new whole-body visuo-tactile stimulation procedure. Fifty non-clinical participants were randomly assigned to synchronous or asynchronous visuo-tactile groups. During the pre-assessment, all participants filled in BIDs and body-anxiety questionnaires. Then, they were embodied into two virtual bodies (VBs): firstly, with their real measurements, and secondly, with a larger-size body. Body image disturbances, body anxiety, fear of gaining weight, and FBI levels were assessed after exposure to each avatar. All participants in both conditions showed higher levels of BIDs and body anxiety after owning the larger-size VB than after owning the real-size VB (p < 0.05). The synchronous visuo-tactile group had higher scores, although the differences did not reach statistical significance. This study provides evidence of the usefulness of this new embodiment-based technique to induce changes in BIDs or body anxiety in a non-clinical sample, being suitable for use in future body image interventions.
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Litwin, Piotr, Beata Zybura, and Paweł Motyka. "Tactile information counteracts the attenuation of rubber hand illusion attributable to increased visuo-proprioceptive divergence." PLOS ONE 15, no. 12 (December 30, 2020): e0244594. http://dx.doi.org/10.1371/journal.pone.0244594.
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Sense of body ownership is an immediate and distinct experience of one’s body as belonging to oneself. While it is well-recognized that ownership feelings emerge from the integration of visual and somatosensory signals, the principles upon which they are integrated are still intensely debated. Here, we used the rubber hand illusion (RHI) to examine how the interplay of visual, tactile, and proprioceptive signals is governed depending on their spatiotemporal properties. For this purpose, the RHI was elicited in different conditions varying with respect to the extent of visuo-proprioceptive divergence (i.e., the distance between the real and fake hands) and differing in terms of the availability and spatiotemporal complexity of tactile stimulation (none, simple, or complex). We expected that the attenuating effect of distance on illusion strength will be more pronounced in the absence of touch (when proprioception gains relatively higher importance) and absent in the presence of complex tactile signals. Additionally, we hypothesized that participants with greater proprioceptive acuity—assessed using an elbow joint position discrimination task—will be less susceptible to the illusion, but only under the conditions of limited tactile stimulation. In line with our prediction, RHI was attenuated at the farthest distance only when tactile information was absent or simplified, but the attenuation was effectively prevented by the use of complex tactile stimulation—in this case, RHI was comparably vivid at both distances. However, passive proprioceptive acuity was not related to RHI strength in either of the conditions. The results indicate that complex-structured tactile signals can override the influence of proprioceptive signals in body attribution processes. These findings extend our understanding of body ownership by showing that it is primarily determined by informative cues from the most relevant sensory domains, rather than mere accumulation of multisensory evidence.
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Sforza, Anna, Ilaria Bufalari, Patrick Haggard, and Salvatore M. Aglioti. "My face in yours: Visuo-tactile facial stimulation influences sense of identity." Social Neuroscience 5, no. 2 (April 2010): 148–62. http://dx.doi.org/10.1080/17470910903205503.
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Segond, Hervé, Déborah Weiss, and Eliana Sampaio. "Human Spatial Navigation via a Visuo-Tactile Sensory Substitution System." Perception 34, no. 10 (October 2005): 1231–49. http://dx.doi.org/10.1068/p3409.
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Spatial navigation within a real 3-D maze was investigated to study space perception on the sole basis of tactile information transmitted by means of a ‘tactile vision substitution system' (TVSS) allowing the conversion of optical images—collected by a micro camera—into ‘tactile images’ via a matrix in contact with the skin. The development of such a device is based on concepts of cerebral and functional plasticity, enabling subjective reproduction of visual images from tactile data processing. Blindfolded sighted subjects had to remotely control the movements of a robot on which the TVSS camera was mounted. Once familiarised with the cues in the maze, the subjects were given two exploration sessions. Performance was analysed according to an objective point of view (exploration time, discrimination capacity), as well as a subjective one (speech). The task was successfully carried out from the very first session. As the subjects took a different path during each navigation, a gradual improvement in performance (discrimination and exploration time) was noted, generating a phenomenon of learning. Moreover, subjective analysis revealed an evolution of the spatialisation process towards distal attribution. Finally, some emotional expressions seemed to reflect the genesis of ‘qualia’ (emotional qualities of stimulation).
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Preatoni, Greta, Francesca Dell’Eva, Giacomo Valle, Alessandra Pedrocchi, and Stanisa Raspopovic. "Reshaping the full body illusion through visuo-electro-tactile sensations." PLOS ONE 18, no. 2 (February 1, 2023): e0280628. http://dx.doi.org/10.1371/journal.pone.0280628.
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The physical boundaries of our body do not define what we perceive as self. This malleable representation arises from the neural integration of sensory information coming from the environment. Manipulating the visual and haptic cues produces changes in body perception, inducing the Full Body Illusion (FBI), a vastly used approach to exploring humans’ perception. After pioneering FBI demonstrations, issues arose regarding its setup, using experimenter-based touch and pre-recorded videos. Moreover, its outcome measures are based mainly on subjective reports, leading to biased results, or on heterogeneous objective ones giving poor consensus on their validity. To address these limitations, we developed and tested a multisensory platform allowing highly controlled experimental conditions, thanks to the leveraged use of innovative technologies: Virtual Reality (VR) and Transcutaneous Electrical Nerve Stimulation (TENS). This enabled a high spatial and temporal precision of the visual and haptic cues, efficiently eliciting FBI. While it matched the classic approach in subjective measures, our setup resulted also in significant results for all objective measurements. Importantly, FBI was elicited when all 4 limbs were multimodally stimulated but also in a single limb condition. Our results behoove the adoption of a comprehensive set of measures, introducing a new neuroscientific platform to investigate body representations.
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Vallar, Giuseppe, Maria Luisa Rusconi, and Bruno Bernardini. "Modulation of neglect hemianesthesia by transcutaneous electrical stimulation." Journal of the International Neuropsychological Society 2, no. 5 (September 1996): 452–59. http://dx.doi.org/10.1017/s1355617700001533.
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AbstractThe effects of transcutaneous electrical stimulation on deficits of tactile perception contralateral to a hemispheric lesion were investigated in 10 right brain-damaged patients and in four left brain-damaged patients. The somatosensory deficit recovered, transiently and in part, after stimulation of the side of the neck contralateral to the side of the lesion, in all 10 patients with lesions in the right hemisphere, both with (six cases) and without (four cases) left visuo-spatial hemineglect, and in one left brain-damaged patient with right hemineglect. In three left brain-damaged patients without hemineglect, the treatment had no detectable effects. In one right brain-damaged patient, the stimulation of the side of the neck ipsilateral to the side of the lesion temporarily worsened the somatosensory deficit. These effects of transcutaneous electrical stimulation are similar to those of vestibular stimulation. The suggestion is made that these treatments modulate, through afferent sensory pathways, higher-order spatial representations of the body, which are pathologically distorted toward the side of the lesion. The modulatory effect is direction-specific: the defective internal representation of the contralesional side may be either partly restored, improving the disorder of tactile perception, or further impoverished, worsening the deficit. The possible neural basis of this modulation is discussed. (JINS, 1996, 2, 452–459.)
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Lunghi, Claudia, and M. Concetta Morrone. "Early Interaction between Vision and Touch during Binocular Rivalry." Multisensory Research 26, no. 3 (2013): 291–306. http://dx.doi.org/10.1163/22134808-00002411.
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Multisensory integration is known to occur at high neural levels, but there is also growing evidence that cross-modal signals can be integrated at the first stages of sensory processing. We investigated whether touch specifically affected vision during binocular rivalry, a particular type of visual bistability that engages neural competition in early visual cortices. We found that tactile signals interact with visual signals outside of awareness, when the visual stimulus congruent with the tactile one is perceptually suppressed during binocular rivalry and when the interaction is strictly tuned for matched visuo-tactile spatial frequencies. We also found that voluntary action does not play a leading role in mediating the effect, since the interaction was observed also when tactile stimulation was passively delivered to the finger. However, simultaneous presentation of visual and tactile stimuli is necessary to elicit the interaction, and an asynchronous priming touch stimulus is not affecting the onset of rivalry. These results point to a very early cross-modal interaction site, probably V1. By showing that spatial proximity between visual and tactile stimuli is a necessary condition for the interaction, we also suggest that the two sensory spatial maps are aligned according to retinotopic coordinates, corroborating the hypothesis of a very early interaction between visual and tactile signals during binocular rivalry.
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Cardini, Flavia, Patrick Haggard, and Elisabetta Ladavas. "Seeing and feeling for self and other: Proprioceptive spatial location determines multisensory enhancement of touch." Seeing and Perceiving 25 (2012): 113. http://dx.doi.org/10.1163/187847612x647469.
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In the Visual Enhancement of Touch (VET), simply viewing one’s hand improves tactile spatial perception, even though vision is non-informative. While previous studies had suggested that looking at another person’s hand could also enhance tactile perception, no previous study had systematically investigated the differences between viewing one’s body and someone else’s. The aim of this study was to shed light on the relation between visuo–tactile interactions and the self-other distinction. In Experiment 1 we manipulated the spatial location where a hand was seen. Viewing one’s hand enhanced tactile acuity relative to viewing a neutral object, but only when the image of the hand was spatially aligned with the actual location of the participant’s unseen hand. The VET effect did not occur when one’s hand was viewed at a location other than that experienced proprioceptively. In contrast, viewing another’s hand produced enhanced tactile perception irrespective of spatial location. In Experiment 2, we used a multisensory stimulation technique, known as Visual Remapping of Touch, to reduce perceived spatial misalignment of vision and touch. When participants saw an image of their own hand being touched at the same time as the tactile stimulation, the reduction in perceived misalignment caused VET effect to return, even though the spatial location of the images was not consistent with the actual body posture. Our results suggest that multisensory modulation of touch depends on a representation of one’s body that is fundamentally spatial in nature. In contrast, representation of others is free from this spatial constraint.
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Tagini, Sofia, Federica Scarpina, Francesca Bruni, Massimo Scacchi, Alessandro Mauro, and Massimiliano Zampini. "The Virtual Hand Illusion in Obesity: Dissociation Between Multisensory Interactions Supporting Illusory Experience and Self-Location Recalibration." Multisensory Research 33, no. 3 (July 1, 2020): 337–61. http://dx.doi.org/10.1163/22134808-20191425.
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Abstract The Rubber Hand Illusion (RHI) is used widely to investigate the multisensory integration mechanisms that support bodily self-consciousness and, more specifically, body ownership and self-location. It has been reported that individuals affected by obesity show anomalous multisensory integration processes. We propose that these obesity-induced changes could lead to an unusual susceptibility to the RHI and anomalous bodily self-experience. To test this hypothesis, we administered a modified version of the RHI (using a picture of the participant’s hand) to individuals affected by obesity and participants with a healthy weight. During synchronous and asynchronous stimulation, we compared the subjective experience of the illusion (using a questionnaire) and the effect of the illusion on self-location (i.e., proprioceptive drift). In accordance with the illusion phenomenology, both groups had a comparable subjective illusory experience after the synchronous stimulation. Nevertheless, individuals affected by obesity showed less recalibration of self-location than healthy weight participants. In light of a recent interpretation of the multisensory integration mechanisms that underpin the RHI, our findings suggest that in obesity visuo-tactile integration supporting the subjective experience of the illusion is preserved, whereas visuo-proprioceptive integration for self-location is reduced.
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Zazio, Agnese, Giacomo Guidali, Ottavia Maddaluno, Carlo Miniussi, and Nadia Bolognini. "Hebbian associative plasticity in the visuo-tactile domain: A cross-modal paired associative stimulation protocol." NeuroImage 201 (November 2019): 116025. http://dx.doi.org/10.1016/j.neuroimage.2019.116025.
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Gordon, Calum, Alba Barbullushi, Stefano Tombolini, Federica Margiotta, Alessia Ciacci, Lama Shekh Yosef, Leon Barker, and Matteo Martini. "Visuo–tactile stimulation, but not type of movement, modulates pain during the vision of a moving virtual limb." Pain Management 9, no. 5 (September 2019): 449–60. http://dx.doi.org/10.2217/pmt-2019-0019.
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Aim: Evidence has revealed a relationship between pain and the observation of limb movement, but it is unknown whether different types of movements have diverse modulating effects. In this immersive virtual reality study, we explored the effect of the vision of different virtual arm movements (arm vs wrist) on heat pain threshold of healthy participants. Patients & methods: 40 healthy participants underwent four conditions in virtual reality, while heat pain thresholds were measured. Visuo–tactile stimulation was used to attempt to modulate the feeling of virtual limb ownership while the participants kept their arms still. Results: Effects on pain threshold were present for type of stimulation but not type of movement. Conclusion: The type of observed movement does not appear to influence pain modulation, at least not during acute pain states.
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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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Dobricki, Martin, Betty J. Mohler, and Heinrich H. Bülthoff. "The structure of self-experience during visuo–tactile stimulation of a virtual and the physical body." Seeing and Perceiving 25 (2012): 214. http://dx.doi.org/10.1163/187847612x648413.
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The simultaneous visuo–tactile stimulation of an individual’s body and a virtual body (avatar) is an experimental method used to investigate the mechanisms of self-experience. Studies incorporating this method found that it elicits the experience of bodily ownership over the avatar. Moreover, as part of our own research we found that it also has an effect on the experience of agency, spatial presence, as well as on the perception of self-motion, and thus on self-localization. However, it has so far not been investigated whether these effects represent distinct categories within conscious experience. We stroked the back of 21 male participants for three minutes while they watched an avatar getting synchronously stroked within a virtual city in a head-mounted display setup. Subsequently, we assessed their avatar and their spatial presence experience with 23 questionnaire items. The analysis of the responses to all items by means of nonmetric multidimensional scaling resulted in a two-dimensional map (stress = 0.151) on which three distinct categories of items could be identified: a cluster (Cronbach’s alpha = 0.89) consisting of all presence items, a cluster (Cronbach’s alpha = 0.88) consisting of agency-related items, and a cluster (Cronbach’s alpha = 0.93) consisting of items related to body ownership as well as self-localization. The reason that spatial presence formed a distinct category could be that body ownership, self-localization and agency are not reported in relation to space. Body ownership and self-localization belonged to the same category which we named identification phenomena. Hence, we propose the following three higher-order categories of self-experience: identification, agency, and spatial presence.
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Spaccasassi, Chiara, Ivana Frigione, and Angelo Maravita. "Bliss in and Out of the Body: The (Extra)Corporeal Space Is Impervious to Social Pleasant Touch." Brain Sciences 11, no. 2 (February 12, 2021): 225. http://dx.doi.org/10.3390/brainsci11020225.
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Slow, gentle stimulation of hairy skin is generally accompanied by hedonic sensations. This phenomenon, also known as (positive) affective touch, is likely to be the basis of affiliative interactions with conspecifics by promoting inter-individual bindings. Previous studies on healthy humans have demonstrated that affective touch can remarkably impact behavior. For instance, by administering the Rubber Hand Illusion (RHI) paradigm, the embodiment of a fake hand enhances after a slow, affective touch compared to a fast, neutral touch. However, results coming from this area are not univocal. In addition, there are no clues in the existing literature on the relationship between affective touch and the space around our body. To overcome these lacks, we carried out two separate experiments where participants underwent a RHI paradigm (Experiment 1) and a Visuo-Tactile Interaction task (Experiment 2), designed to tap into body representation and peripersonal space processing, respectively. In both experiments, an affective touch (CT-optimal, 3 cm/s) and neutral touch (CT-suboptimal, 18 cm/s) were delivered by the experimenter on the dorsal side of participants’ hand through a “skin to skin” contact. In Experiment 1, we did not find any modulation of body representation—not at behavioral nor at a physiological level—by affective touch. In Experiment 2, no visuo-tactile spatial modulation emerged depending upon the pleasantness of the touch received. These null findings are interpreted in the light of the current scientific context where the real nature of affective touch is often misguided, and they offer the possibility to pave the way for understanding the real effects of affective touch on body/space representation.
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Teaford, Max, Jason Gilliland, Olivia Hodkey, Tara McVeigh, Caleb Perry, Lyric Rains-Bury, and L. James Smart. "Preliminary Evaluation of the Moving Rubber Foot Illusion in a Sample of Female University Students." Perception 50, no. 11 (November 2021): 966–75. http://dx.doi.org/10.1177/03010066211058802.
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The Rubber Foot Illusion (RFI) is an illusion in which one is made to feel that a model foot is their own through synchronous visuo-tactile stimulation. Previous research suggests that the conditions the RFI can be elicited under are similar to those of the Rubber Hand Illusion (RHI). However, it was unknown if the RFI could be elicited by synchronous movement of a participant’s foot and a model foot. To examine this, we developed the Moving Rubber Foot Illusion (mRFI) and compared participants’ experience of it to the RFI. The results of this study suggests that the RFI can be elicited through synchronous movement, and results in more proprioceptive drift than a static variant of the RFI. More work is needed to better understand the mechanisms underlying the mRFI.
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Provenzano, Luca, Giuseppina Porciello, Sofia Ciccarone, Bigna Lenggenhager, Gaetano Tieri, Matteo Marucci, Federico Dazzi, Camillo Loriedo, and Ilaria Bufalari. "Characterizing Body Image Distortion and Bodily Self-Plasticity in Anorexia Nervosa via Visuo-Tactile Stimulation in Virtual Reality." Journal of Clinical Medicine 9, no. 1 (December 30, 2019): 98. http://dx.doi.org/10.3390/jcm9010098.
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We combined virtual reality and multisensory bodily illusion with the aim to characterize and reduce the perceptual (body overestimation) and the cognitive-emotional (body dissatisfaction) components of body image distortion (BID) in anorexia nervosa (AN). For each participant (20 anorexics, 20 healthy controls) we built personalized avatars that reproduced their own body size, shape, and verisimilar increases and losses of their original weight. Body overestimation and dissatisfaction were measured by asking participants to choose the avatar that best resembled their real and ideal body. Results show higher body dissatisfaction in AN, caused by the desire of a thinner body, and no body-size overestimation. Interpersonal multisensory stimulation (IMS) was then applied on the avatar reproducing participant’s perceived body, and on the two avatars which reproduced increases and losses of 15% of it, all presented with a first-person perspective (1PP). Embodiment was stronger after synchronous IMS in both groups, but did not reduce BID in participants with AN. Interestingly, anorexics reported more negative emotions after embodying the fattest avatar, which scaled with symptoms severity. Overall, our findings suggest that the cognitive-emotional, more than the perceptual component of BID is severely altered in AN and that perspective (1PP vs. 3PP) from which a body is evaluated may play a crucial role. Future research and clinical trials might take advantage of virtual reality to reduce the emotional distress related to body dissatisfaction.
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Padilla-Castañeda, Miguel A., Antonio Frisoli, Silvia Pabon, and Massimo Bergamasco. "The Modulation of Ownership and Agency in the Virtual Hand Illusion under Visuotactile and Visuomotor Sensory Feedback." Presence: Teleoperators and Virtual Environments 23, no. 2 (August 1, 2014): 209–25. http://dx.doi.org/10.1162/pres_a_00181.
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It is well known by the virtual hand illusion (VHI) that simultaneous and synchronous visuotactile sensory feedback within a virtual environment elicits the feeling of ownership of a virtual hand, by observing for some seconds in a scene a virtual hand being touched while at the same time receiving tactile stimulation on the real hand in the corresponding positions. In this paper, we investigate possible modulations in the feeling of ownership (sensation of owning a virtual hand) and of agency (sensation of owning virtual movements and actions) according to whether or not the participant's own motor acts (1) induce coherent self-activated visuotactile sensory stimulations; and (2) generate plausible consequences in the simulated environment. For this purpose, we elicited the VHI within a group of participants through a cross-modal integration of visuo-tactile sensory stimulations within a dynamic and physically plausible immersive virtual environment, where they were able to perform natural tasks in both passive and active agency conditions. Our results indicate that both feelings of ownership and agency can be achieved in immersive virtual environments, when the subject is realistically interacting and performing natural upper limb movements. We did not observe any significant difference in the VHI in terms of ownership and agency between the active and passive conditions, but we observed that a physically incongruent simulated interaction with the virtual world can lead to a significant disruption of ownership. Moreover, in the passive agency condition, a plausible physical behavior of the virtual hand was sufficient to elicit a partially complete sense of ownership, if measured in terms of proprioceptive drift, even in the presence of an asynchronous visuotactile sensory feedback. All these findings suggest that the multisensory feedback associated with a subject's own actions and the physical plausibility of the environment both act as determinant factors, influencing and modulating the vividness of the VHI.
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Porras-Garcia, Bruno, Marta Ferrer-Garcia, Eduardo Serrano-Troncoso, Marta Carulla-Roig, Pau Soto-Usera, Helena Miquel-Nabau, Nazilla Shojaeian, et al. "Validity of Virtual Reality Body Exposure to Elicit Fear of Gaining Weight, Body Anxiety and Body-Related Attentional Bias in Patients with Anorexia Nervosa." Journal of Clinical Medicine 9, no. 10 (October 5, 2020): 3210. http://dx.doi.org/10.3390/jcm9103210.
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Fear of gaining weight (FGW), body image disturbances, associated anxiety and body-related attentional bias are the core symptoms of anorexia nervosa (AN) and play critical roles in its development and maintenance. The aim of the current study is to evaluate the usefulness of virtual reality-based body exposure software for the assessment of important body-related cognitive and emotional responses in AN. Thirty female patients with AN, one of them subclinical, and 43 healthy college women, 25 with low body dissatisfaction (BD) and 18 with high BD, owned a virtual body that had their silhouette and body mass index. Full-body illusion (FBI) over the virtual body was induced using both visuo-motor and visuo-tactile stimulation. Once the FBI was induced, the FBI itself, FGW, body anxiety and body-related attentional bias toward weight-related and non-weight-related body areas were assessed. One-way analyses of covariance (ANCOVA), controlling for age, showed that AN patients reported higher FGW, body anxiety and body-related attentional bias than healthy controls. Unexpectedly, patients with AN reported significantly lower FBI levels than healthy participants. Finally, Pearson correlations showed significant relationships between visual analog scales and body-related attentional bias measures, compared to other eating disorder measures. These results provide evidence about the usefulness of virtual reality-based body exposure to elicit FGW and other body-related disturbances in AN patients. Thus, it may be a suitable intervention for reducing these emotional responses and for easing weight recovery.
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Gentili, Sandro, Maria Richetta, Stefano Mugnaini, S. Mancini, and Enrico M. Staderini. "The Use of Vibrotactile Stimulation for Improving Manual Tasks in Parkinson's Disease Patients." Materials Science Forum 879 (November 2016): 2348–51. http://dx.doi.org/10.4028/www.scientific.net/msf.879.2348.
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In spite of the potentially harmful effects of vibrations on the human body, a new path was recently opened for the use of these mechanical means in the therapeutic field. The stimulation of proprioceptive and exteroceptive sensitivity is the main target in both peripheral (diabetes type 1 and type 2) and central (stroke, Parkinson's disease multiple sclerosis) nervous system disorders, particularly for the recovery and maintenance of functional state. By the way the response to the treatment is highly variable from subject to subject. Our experimental apparatus consists of a virtual reality system "LEAP Motion" which involves the patient in the execution of visuo-manual tasks in a virtual environment while receiving vibrotactile stimulation. We also used a modular 36 channels EEG system and a vibratory stimulation system able of delivering vibratory stimuli perpendicular and tangential to the body surface area.The study evaluation of motor performance and the ability to perform the tasks of visuomotor task assigned, in the presence and absence of vibratory stimulation and in real time, evoked potentials in the cortex.The vibration frequency extended from 5 to 200 Hz and with accelerations between 0.3G and 1,5G with displacement amplitude of about 0.5 mm applied on the affected limb hand. As the frequency, the amplitude and the direction of the vibration may vary we studied the relationship between the characteristics of the stimulus and the perception in the cerebral cortex, or other levels of the nervous system, studying potential models of elicitation of the somatosensory system. In this regard, our study took into account patients with Parkinson's disease and in particular evoked potentials N18 N20 N24 N30 particularly related to tactile stimulus, and indicative of the level of perception and processing in the brain of the Parkinson's patient.
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Litwin, Piotr. "Extending Bayesian Models of the Rubber Hand Illusion." Multisensory Research 33, no. 2 (January 8, 2020): 127–60. http://dx.doi.org/10.1163/22134808-20191440.
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Abstract Human body sense is surprisingly flexible — in the Rubber Hand Illusion (RHI), precisely administered visuo-tactile stimulation elicits a sense of ownership over a fake hand. The general consensus is that there are certain semantic top-down constraints on which objects may be incorporated in this way: in particular, to-be-embodied objects should be structurally similar to a visual representation stored in an internal body model. However, empirical evidence shows that the sense of ownership may extend to objects strikingly distinct in morphology and structure (e.g., robotic arms) and the hypothesis about the relevance of appearance lacks direct empirical support. Probabilistic multisensory integration approaches constitute a promising alternative. However, the recent Bayesian models of RHI limit too strictly the possible factors influencing likelihood and prior probability distributions. In this paper, I analyse how Bayesian models of RHI could be extended. The introduction of skin-based spatial information can account for the cross-compensation of sensory signals giving rise to RHI. Furthermore, addition of Bayesian Coupling Priors, depending on (1) internal learned models of relatedness (coupling strength) of sensory cues, (2) scope of temporal binding windows, and (3) extension of peripersonal space, would allow quantification of individual tendencies to integrate divergent visual and somatosensory signals. The extension of Bayesian models would yield an empirically testable proposition accounting comprehensively for a wide spectrum of RHI-related phenomena and rendering appearance-oriented internal body models explanatorily redundant.
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Caola, Barbara, Martina Montalti, Alessandro Zanini, Antony Leadbetter, and Matteo Martini. "The Bodily Illusion in Adverse Conditions: Virtual Arm Ownership During Visuomotor Mismatch." Perception 47, no. 5 (February 23, 2018): 477–91. http://dx.doi.org/10.1177/0301006618758211.
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Classically, body ownership illusions are triggered by cross-modal synchronous stimulations, and hampered by multisensory inconsistencies. Nonetheless, the boundaries of such illusions have been proven to be highly plastic. In this immersive virtual reality study, we explored whether it is possible to induce a sense of body ownership over a virtual body part during visuomotor inconsistencies, with or without the aid of concomitant visuo-tactile stimulations. From a first-person perspective, participants watched a virtual tube moving or an avatar’s arm moving, with or without concomitant synchronous visuo-tactile stimulations on their hand. Three different virtual arm/tube speeds were also investigated, while all participants kept their real arms still. The subjective reports show that synchronous visuo-tactile stimulations effectively counteract the effect of visuomotor inconsistencies, but at slow arm movements, a feeling of body ownership might be successfully induced even without concomitant multisensory correspondences. Possible therapeutical implications of these findings are discussed.
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Rosenblum, Lisa, Alexander Kreß, Jakob C. B. Schwenk, and Frank Bremmer. "Visuo-tactile heading perception." Journal of Neurophysiology, October 19, 2022. http://dx.doi.org/10.1152/jn.00231.2022.
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Self-motion through an environment induces various sensory signals, i.e., visual, vestibular, auditory, or tactile. Numerous studies have investigated the role of visual and vestibular stimulation for the perception of self-motion direction (heading). Here, we investigated the rarely considered interaction of visual and tactile stimuli in heading perception. Participants were presented optic flow simulating forward self-motion across a horizontal ground plane (visual) or airflow towards the participants' forehead (tactile), or both. In separate blocks of trials, participants indicated perceived heading from unimodal visual, tactile, or bimodal sensory signals. In bimodal trials, presented headings were either spatially congruent or incongruent with a maximum offset between visual and tactile heading of 30°. To investigate the reference frame in which visuo-tactile heading is encoded, we varied head and eye orientation during presentation of the stimuli. Visual and tactile stimuli were designed to achieve comparable heading accuracies between modalities. Nevertheless, in bimodal trials, heading perception was dominated by the visual stimulus. A change of head orientation had no significant effect on perceived heading, while, surprisingly, a change in eye orientation affected tactile heading perception. Overall, we conclude that tactile flow is more important to heading perception than previously thought.
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Pratviel, Yvan, Alix Bouni, Véronique Deschodt-Arsac, Florian Larrue, and Laurent M. Arsac. "Avatar embodiment in VR: Are there individual susceptibilities to visuo-tactile or cardio-visual stimulations?" Frontiers in Virtual Reality 3 (September 6, 2022). http://dx.doi.org/10.3389/frvir.2022.954808.
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Virtual reality has obvious potential to help humans developing/recovering brain functions, which operates through modulation of multisensory inputs. Some interventions using VR rely on the need to embody a virtual avatar, which stimulates cognitive-motor adaptations. Recent research has shown that embodiment can be facilitated by synchronizing natural sensory inputs with their visual redundancy on the avatar, e.g., the user’s heartbeat flashing around its avatar (cardio-visual stimulation) or the user’s body being physically stroked while the avatar is touched in synchronized conditions (visuo-tactile stimulation). While different full-body illusions have proven obvious interest in health and disease, it is unknown to date whether individual susceptibilities to illusion are equivalent with respect to cardio-visual or visuo-tactile stimulations. In fact, a number of factors like interoception, vestibular processing, a pronounced visual dependence, a specific cognitive ability for mental rotations, or user traits and habits like empathy and video games practice may interfere with the multifaceted construct of bodily self-consciousness, the conscious experience of owning a body in space from which the world is perceived. Here, we evaluated a number of dispositions in twenty-nine young and healthy participants submitted alternatively to cardio-visual and visuo-tactile stimulations to induce full-body illusions. Three components of bodily self-consciousness consensually identified in recent research, namely self-location, perspective taking and self-identification were quantified by self-reported feeling (questionnaires), and specific VR tasks used before and after multisensory stimulations. VR tasks allowed measuring self-location in reference to a virtual ball rolling toward the participant, perspective taking through visuomotor response times when mentally rotating an avatar suddenly presented at different angles, and self-identification through heart rate dynamics in response to a threatening stimulus applied to the (embodied) avatar. Full-body illusion was evidenced by self-reported quotations of self-identification to the avatar reaching scores in agreement with the literature, lower reaction times when taking the perspective of the avatar and a marked drop in heart rate showing obvious freezing reaction changes when the user saw the avatar being pierced by a spear. Changes in bodily self-consciousness components are not significantly dependent on the type of multisensory stimulation (visuo-tactile or cardio-visual). A principal component analysis demonstrated the lack of covariation between those components, pointing to the relative independence of self-location, perspective taking and self-identification measurements. Moreover, none of these components showed significant covariations with any of the individual dispositions. These results support the hypothesis that cardio-visual and visuo-tactile stimulations affect the main components of bodily self-consciousness in an extent that, in average, is mostly independent of individual perceptive-cognitive profiles, at least in healthy young people. Although this is an important observation at group level, which indicates a similar probability of inducing embodiment with either cardio-visual or visuo-tactile stimulations in VR, these results do not discard the fact that some individuals might have higher susceptibility to specific sensory inputs, which would represent a target to adapt efficient VR stimulations.
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Ono, Mikoto, Nobuyuki Hirose, and Shuji Mori. "Tactile information affects alternating visual percepts during binocular rivalry using naturalistic objects." Cognitive Research: Principles and Implications 7, no. 1 (May 11, 2022). http://dx.doi.org/10.1186/s41235-022-00390-w.
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Abstract Introduction Past studies have provided evidence that the effects of tactile stimulation on binocular rivalry are mediated by primitive features (orientation and spatial frequency) common in vision and touch. In this study, we examined whether such effects on binocular rivalry can be obtained through the roughness of naturalistic objects. In three experiments, the total dominant time of visual percepts of two objects was measured under binocular rivalry when participants touched one of the objects. Result In Experiment 1, the total dominant time for the image of artificial turf and bathmat was prolonged by congruent tactile stimulation and shortened by incongruent tactile stimulation. In Experiment 2, we used the same stimuli but rotated their visual images in opposite directions. The dominant time for either image was prolonged by congruent tactile stimulation. In Experiment 3, we used different types of stimuli, smooth marble and rough fabric, and noted significant effects of the congruent and incongruent tactile stimulation on the dominant time of visual percepts. Conclusion These three experiments demonstrated that visuo-tactile interaction on binocular rivalry can be mediated by roughness.
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Farizon, D., P. F. Dominey, and J. Ventre-Dominey. "Insights on embodiment induced by visuo-tactile stimulation during robotic telepresence." Scientific Reports 11, no. 1 (November 22, 2021). http://dx.doi.org/10.1038/s41598-021-02091-8.
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AbstractUsing a simple neuroscience-inspired procedure to beam human subjects into robots, we previously demonstrated by visuo-motor manipulations that embodiment into a robot can enhance the acceptability and closeness felt towards the robot. In that study, the feelings of likeability and closeness toward the robot were significantly related to the sense of agency, independently of the sensations of enfacement and location. Here, using the same paradigm we investigated the effect of a purely sensory manipulation on the sense of robotic embodiment associated to social cognition. Wearing a head-mounted display, participants saw the visual scene captured from the robot eyes. By positioning a mirror in front of the robot, subjects saw themselves as a robot. Tactile stimulation was provided by stroking synchronously or not with a paintbrush the same location of the subject and robot faces. In contrast to the previous motor induction of embodiment which particularly affected agency, tactile induction yields more generalized effects on the perception of ownership, location and agency. Interestingly, the links between positive social feelings towards the robot and the strength of the embodiment sensations were not observed. We conclude that the embodiment into a robot is not sufficient in itself to induce changes in social cognition.
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Chen, Siyi, Zhuanghua Shi, Hermann J. Müller, and Thomas Geyer. "Multisensory visuo-tactile context learning enhances the guidance of unisensory visual search." Scientific Reports 11, no. 1 (May 3, 2021). http://dx.doi.org/10.1038/s41598-021-88946-6.
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AbstractDoes multisensory distractor-target context learning enhance visual search over and above unisensory learning? To address this, we had participants perform a visual search task under both uni- and multisensory conditions. Search arrays consisted of one Gabor target that differed from three homogeneous distractors in orientation; participants had to discriminate the target’s orientation. In the multisensory session, additional tactile (vibration-pattern) stimulation was delivered to two fingers of each hand, with the odd-one-out tactile target and the distractors co-located with the corresponding visual items in half the trials; the other half presented the visual array only. In both sessions, the visual target was embedded within identical (repeated) spatial arrangements of distractors in half of the trials. The results revealed faster response times to targets in repeated versus non-repeated arrays, evidencing ‘contextual cueing’. This effect was enhanced in the multisensory session—importantly, even when the visual arrays presented without concurrent tactile stimulation. Drift–diffusion modeling confirmed that contextual cueing increased the rate at which task-relevant information was accumulated, as well as decreasing the amount of evidence required for a response decision. Importantly, multisensory learning selectively enhanced the evidence-accumulation rate, expediting target detection even when the context memories were triggered by visual stimuli alone.
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Teaford, Max, Jared Fitzpatrick, and L. James Smart. "The Impact of Experimentally Induced Limb Ischemia on the Rubber Hand Illusion." Perception, December 7, 2020, 030100662097779. http://dx.doi.org/10.1177/0301006620977797.
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The rubber hand illusion (RHI) is a perceptual illusion in which one experiences an object as part of their body when synchronous visuo-tactile stimulation is applied to one’s hand and the object. There are a variety of factors that can impact the occurrence of the RHI. In the present study, we demonstrate that experimentally induced peripheral ischemia can impact the RHI, namely it can result in larger alterations to the perceived position of one’s hand. This study suggests that alterations to the cardiovascular system may be a source of individual differences in the RHI literature. Future studies with samples of individuals with cardiovascular pathology are recommended.
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Rossi Sebastiano, Alice, Irene Ronga, Carlotta Fossataro, Mattia Galigani, Karol Poles, and Francesca Garbarini. "Multisensory-driven facilitation within the peripersonal space is modulated by the expectations about stimulus location on the body." Scientific Reports 12, no. 1 (November 21, 2022). http://dx.doi.org/10.1038/s41598-022-21469-w.
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AbstractCompelling evidence from human and non-human studies suggests that responses to multisensory events are fastened when stimuli occur within the space surrounding the bodily self (i.e., peripersonal space; PPS). However, some human studies did not find such effect. We propose that these dissonant voices might actually uncover a specific mechanism, modulating PPS boundaries according to sensory regularities. We exploited a visuo-tactile paradigm, wherein participants provided speeded responses to tactile stimuli and rated their perceived intensity while ignoring simultaneous visual stimuli, appearing near the stimulated hand (VTNear) or far from it (VTFar; near the non-stimulated hand). Tactile stimuli could be delivered only to one hand (unilateral task) or to both hands randomly (bilateral task). Results revealed that a space-dependent multisensory enhancement (i.e., faster responses and higher perceived intensity in VTNear than VTFar) was present when highly predictable tactile stimulation induced PPS to be circumscribed around the stimulated hand (unilateral task). Conversely, when stimulus location was unpredictable (bilateral task), participants showed a comparable multisensory enhancement in both bimodal conditions, suggesting a PPS widening to include both hands. We propose that the detection of environmental regularities actively shapes PPS boundaries, thus optimizing the detection and reaction to incoming sensory stimuli.
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Odermatt, Ingrid A., Karin A. Buetler, Nicolas Wenk, Özhan Özen, Joaquin Penalver-Andres, Tobias Nef, Fred W. Mast, and Laura Marchal-Crespo. "Congruency of Information Rather Than Body Ownership Enhances Motor Performance in Highly Embodied Virtual Reality." Frontiers in Neuroscience 15 (July 2, 2021). http://dx.doi.org/10.3389/fnins.2021.678909.
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In immersive virtual reality, the own body is often visually represented by an avatar. This may induce a feeling of body ownership over the virtual limbs. Importantly, body ownership and the motor system share neural correlates. Yet, evidence on the functionality of this neuroanatomical coupling is still inconclusive. Findings from previous studies may be confounded by the congruent vs. incongruent multisensory stimulation used to modulate body ownership. This study aimed to investigate the effect of body ownership and congruency of information on motor performance in immersive virtual reality. We aimed to modulate body ownership by providing congruent vs. incongruent visuo-tactile stimulation (i.e., participants felt a brush stroking their real fingers while seeing a virtual brush stroking the same vs. different virtual fingers). To control for congruency effects, unimodal stimulation conditions (i.e., only visual or tactile) with hypothesized low body ownership were included. Fifty healthy participants performed a decision-making (pressing a button as fast as possible) and a motor task (following a defined path). Body ownership was assessed subjectively with established questionnaires and objectively with galvanic skin response (GSR) when exposed to a virtual threat. Our results suggest that congruency of information may decrease reaction times and completion time of motor tasks in immersive virtual reality. Moreover, subjective body ownership is associated with faster reaction times, whereas its benefit on motor task performance needs further investigation. Therefore, it might be beneficial to provide congruent information in immersive virtual environments, especially during the training of motor tasks, e.g., in neurorehabilitation interventions.
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Grewe, C. Martin, Tuo Liu, Andrea Hildebrandt, and Stefan Zachow. "The Open Virtual Mirror Framework for enfacement illusions." Behavior Research Methods, May 2, 2022. http://dx.doi.org/10.3758/s13428-021-01761-9.
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AbstractEnfacement illusions are traditionally elicited by visuo-tactile stimulation, but more active paradigms become possible through the usage of virtual reality techniques. For instance, virtual mirrors have been recently proposed to induce enfacement by visuo-motor stimulation. In a virtual mirror experiment, participants interact with an avatar that imitates their facial movements. The active control over the avatar greatly enhances the sense of agency, which is an important ingredient for successful enfacement illusion induction. Due to technological challenges, most virtual mirrors so far were limited to the imitation of the participant’s head pose, i.e., its location and rotation. However, stronger experiences of agency can be expected by an increase in the avatar’s mimicking abilities. We here present a new open-source framework for virtual mirror experiments, which we call the Open Virtual Mirror Framework (OVMF). The OVMF can track and imitate a large range of facial movements, including pose and expressions. It has been designed to run on standard computer hardware and easily interfaces with existing toolboxes for psychological experimentation, while satisfying the requirement of a tightly controlled experimental setup. Further, it is designed to enable convenient extension of its core functionality such that it can be flexibly adjusted to many different experimental paradigms. We demonstrate the usage of the OVMF and experimentally validate its ability to elicit experiences of agency over an avatar, concluding that the OVMF can serve as a reference for future experiments and that it provides high potential to stimulate new directions in enfacement research and beyond.
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Panagiotopoulou, Elena, Laura Crucianelli, Alessandra Lemma, and Aikaterini Fotopoulou. "Identifying with the beautiful: Facial attractiveness effects on unisensory and multisensory self–other distinction." Quarterly Journal of Experimental Psychology, October 13, 2021, 174702182110503. http://dx.doi.org/10.1177/17470218211050318.
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People tend to evaluate their own traits and abilities favourably and such favourable self-perceptions extend to attractiveness. However, the exact mechanism underlying this self-enhancement bias remains unclear. One possibility could be the identification with attractive others through blurring of self–other boundaries. Across two experiments, we used the enfacement illusion to investigate the effect of others’ attractiveness in the multisensory perception of the self. In Experiment 1 ( N = 35), participants received synchronous or asynchronous interpersonal visuo-tactile stimulation with an attractive and non-attractive face. In Experiment 2 ( N = 35), two new faces were used and spatial incongruency was introduced as a control condition. The results showed that increased ratings of attractiveness of an unfamiliar face lead to blurring of self–other boundaries, allowing the identification of our psychological self with another’s physical self and specifically their face, and this seems to be unrelated to perceived own attractiveness. The effect of facial attractiveness on face ownership showed dissociable mechanisms, with multisensory integration modulating the effect on similarity but not identification, an effect that may be purely based on vision. Overall, our findings suggest that others’ attractiveness may lead to positive distortions of the self. This research provides a psychophysical starting point for studying the impact of others’ attractiveness on self-face recognition, which can be particularly important for individuals with malleable, embodied self–other boundaries and body image disturbances.
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Panagiotopoulou, Elena, Laura Crucianelli, Alessandra Lemma, and Aikaterini Fotopoulou. "Identifying with the beautiful: Facial attractiveness effects on unisensory and multisensory self–other distinction." Quarterly Journal of Experimental Psychology, October 13, 2021, 174702182110503. http://dx.doi.org/10.1177/17470218211050318.
Full textAbstract:
People tend to evaluate their own traits and abilities favourably and such favourable self-perceptions extend to attractiveness. However, the exact mechanism underlying this self-enhancement bias remains unclear. One possibility could be the identification with attractive others through blurring of self–other boundaries. Across two experiments, we used the enfacement illusion to investigate the effect of others’ attractiveness in the multisensory perception of the self. In Experiment 1 ( N = 35), participants received synchronous or asynchronous interpersonal visuo-tactile stimulation with an attractive and non-attractive face. In Experiment 2 ( N = 35), two new faces were used and spatial incongruency was introduced as a control condition. The results showed that increased ratings of attractiveness of an unfamiliar face lead to blurring of self–other boundaries, allowing the identification of our psychological self with another’s physical self and specifically their face, and this seems to be unrelated to perceived own attractiveness. The effect of facial attractiveness on face ownership showed dissociable mechanisms, with multisensory integration modulating the effect on similarity but not identification, an effect that may be purely based on vision. Overall, our findings suggest that others’ attractiveness may lead to positive distortions of the self. This research provides a psychophysical starting point for studying the impact of others’ attractiveness on self-face recognition, which can be particularly important for individuals with malleable, embodied self–other boundaries and body image disturbances.
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Tekgün, Ege, and Burak Erdeniz. "Contributions of Body-Orientation to Mental Ball Dropping Task During Out-of-Body Experiences." Frontiers in Integrative Neuroscience 15 (January 4, 2022). http://dx.doi.org/10.3389/fnint.2021.781935.
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Out-of-body experiences (OBEs) provide fascinating insights into our understanding of bodily self-consciousness and the workings of the brain. Studies that examined individuals with brain lesions reported that OBEs are generally characterized by participants experiencing themselves outside their physical body (i.e., disembodied feeling) (Blanke and Arzy, 2005). Based on such a characterization, it has been shown that it is possible to create virtual OBEs in immersive virtual environments (Ehrsson, 2007; Ionta et al., 2011b; Bourdin et al., 2017). However, the extent to which body-orientation influences virtual OBEs is not well-understood. Thus, in the present study, 30 participants (within group design) experienced a full-body ownership illusion (synchronous visuo-tactile stimulation only) induced with a gender-matched full-body virtual avatar seen from the first-person perspective (1PP). At the beginning of the experiment, participants performed a mental ball dropping (MBD) task, seen from the location of their virtual avatar, to provide a baseline measurement. After this, a full-body ownership illusion (embodiment phase) was induced in all participants. This was followed by the virtual OBE illusion phase of the experiment (disembodiment phase) in which the first-person viewpoint was switched to a third-person perspective (3PP), and participants' disembodied viewpoint was gradually raised to 14 m above the virtual avatar, from which altitude they repeated the MBD task. During the experiment, this procedure was conducted twice, and the participants were allocated first to the supine or the standing body position at random. Results of the MBD task showed that the participants experienced increased MBD durations during the supine condition compared to the standing condition. Furthermore, although the findings from the subjective reports confirmed the previous findings of virtual OBEs, no significant difference between the two postures was found for body ownership. Taken together, the findings of the current study make further contributions to our understanding of both the vestibular system and time perception during OBEs.
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Pamplona, Gustavo S. P., Julio A. D. Salgado, Philipp Staempfli, Erich Seifritz, Roger Gassert, and Silvio Ionta. "Illusory Body Ownership Affects the Cortical Response to Vicarious Somatosensation." Cerebral Cortex, July 8, 2021. http://dx.doi.org/10.1093/cercor/bhab210.
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Abstract Fundamental human feelings such as body ownership (“this” body is “my” body) and vicariousness (first-person-like experience of events occurring to others) are based on multisensory integration. Behavioral links between body ownership and vicariousness have been shown, but the neural underpinnings remain largely unexplored. To fill this gap, we investigated the neural effects of altered body ownership on vicarious somatosensation. While recording functional brain imaging data, first, we altered participants’ body ownership by robotically delivering tactile stimulations (“tactile” stroking) in synchrony or not with videos of a virtual hand being brushed (“visual” stroking). Then, we manipulated vicarious somatosensation by showing videos of the virtual hand being touched by a syringe’s plunger (touch) or needle (pain). Only after the alteration of body ownership (synchronous visuo-tactile stroking) and specifically during late epochs of vicarious somatosensation, vicarious pain was associated with lower activation in premotor and anterior cingulate cortices with respect to vicarious touch. At the methodological level, the present study highlights the importance of the neural response’s temporal evolution. At the theoretical level, it shows that the higher-level (cognitive) impact of a lower-level (sensory) body-related processing (visuo-tactile) is not limited to body ownership but also extends to other psychological body-related domains, such as vicarious somatosensation.
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Romano, Daniele, Angelo Maravita, and Marco Perugini. "Psychometric properties of the embodiment scale for the rubber hand illusion and its relation with individual differences." Scientific Reports 11, no. 1 (March 3, 2021). http://dx.doi.org/10.1038/s41598-021-84595-x.
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AbstractThe Rubber Hand Illusion (RHI) opened the investigation of the sense of body ownership in healthy people. By putting in slight contrast vision touch and proprioception, healthy people embody a fake hand in one's body representation. The easiness of the procedure, typically measured with a set of questions that capture the subjective experience, favoured its blooming. However, validation studies of embodiment questionnaires are lacking, and the individual differences that contribute to the embodiment received little attention. In our study, 298 participants underwent an RHI procedure following both synchronous and asynchronous (control) visuo-tactile stimulations. The study had multiple aims: (a) to explore the psychometric structure of a 27-items questionnaire largely used in the literature; (b) to build a psychometrically efficient scale to measure embodiment-related phenomena; (c) to explore whether and how individual differences (empathy, self-esteem and mindfulness) are associated with the experience of illusion. We found a relatively simple structure consisting of three components: embodiment of the rubber hand, disembodiment of the biological hand, physical sensations experienced during the procedure. The scales designed were psychometrically reliable and theoretically meaningful, encompassing 18 of the original items. Finally, by adopting a network analysis approach, we found that the embodiment is directly related to empathy and self-esteem, while disembodiment and physical sensation are unrelated to individual personality traits. The study provides substantial evidence to use the embodiment scale as a standard questionnaire for future RHI studies. Additionally, the correlations with personality traits suggest that the embodiment induced by the RHI deeply integrates with the complexity of the individuals and their differences.