25 research outputs found
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Moving a Rubber Hand that Feels Like Your Own: A Dissociation of Ownership and Agency
During voluntary hand movement, we sense that we generate the movement and that the hand is a part of our body. These feelings of control over bodily actions, or the sense of agency, and the ownership of body parts are two fundamental aspects of the way we consciously experience our bodies. However, little is known about how these processes are functionally linked. Here, we introduce a version of the rubber hand illusion in which participants control the movements of the index finger of a model hand, which is in full view, by moving their own right index finger. We demonstrated that voluntary finger movements elicit a robust illusion of owning the rubber hand and that the senses of ownership and agency over the model hand can be dissociated. We systematically varied the relative timing of the finger movements (synchronous versus asynchronous), the mode of movement (active versus passive), and the position of the model hand (anatomically congruent versus incongruent positions). Importantly, asynchrony eliminated both ownership and agency, passive movements abolished the sense of agency but left ownership intact, and incongruent positioning of the model hand diminished ownership but did not eliminate agency. These findings provide evidence for a double dissociation of ownership and agency, suggesting that they represent distinct cognitive processes. Interestingly, we also noted that the sense of agency was stronger when the hand was perceived to be a part of the body, and only in this condition did we observe a significant correlation between the subjects’ ratings of agency and ownership. We discuss this in the context of possible differences between agency over owned body parts and agency over actions that involve interactions with external objects. In summary, the results obtained in this study using a simple moving rubber hand illusion paradigm extend previous findings on the experience of ownership and agency and shed new light on their relationship
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Priming letters by colors: evidence for the bidirectionality of grapheme–color synesthesia
In synesthesia, stimulation of one sensory modality leads to a percept in another nonstimulated modality, for example, graphemes trigger an additional color percept in grapheme–color synesthesia, which encompasses the variants letter–color and digit–color synesthesia. Until recently, it was assumed that synesthesia occurs strictly unidirectional: Although the perception of a letter induces a color percept in letter–color synesthetes, they typically do not report that colors trigger the percept of a letter. Recent data on number processing in synesthesia suggest, however, that colors can implicitly elicit numerical representations in digit–color synesthetes, thereby questioning unidirectional models of synesthesia. Using a word fragment completion paradigm in 10 letter–color synesthetes, we show here for the first time that colors can implicitly influence lexical search. Our data provide strong support for a bidirectional nature of grapheme–color synesthesia and, in general, may allude to the mechanisms of cross-modality interactions in the human brain
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The spatial distance rule in the moving and classical rubber hand illusions
The rubber hand illusion (RHI) is a perceptual illusion in which participants perceive a model hand as part of their own body. Here, through the use of one questionnaire experiment and two proprioceptive drift experiments, we investigated the effect of distance (12, 27.5, and 43 cm) in the vertical plane on both the moving and classical RHI. In both versions of the illusion, we found an effect of distance on ownership of the rubber hand for both measures tested. Our results further suggested that the moving RHI might follow a narrower spatial rule. Finally, whereas ownership of the moving rubber hand was affected by distance, this was not the case for agency, which was present at all distances tested. In sum, the present results generalize the spatial distance rule in terms of ownership to the vertical plane of space and demonstrate that also the moving RHI obeys this rule
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Neural correlates of the rubber hand illusion in amputees: a report of two cases
One of the current challenges in the field of advanced prosthetics is the development of artificial limbs that provide
the user with detailed sensory feedback. Sensory feedback from our limbs is not only important for proprioceptive
awareness and motor control, but also essential for providing us with a feeling of ownership or simply put, the
sensation that our limbs actually belong to ourselves. The strong link between sensory feedback and ownership
has been repeatedly demonstrated with the so-called rubber hand illusion (RHI), during which individuals are
induced with the illusory sensation that an artificial hand is their own. In healthy participants, this occurs via
integration of visual and tactile signals, which is primarily supported by multisensory regions in premotor and
intraparietal cortices. Here, we describe a functional magnetic resonance imaging (fMRI) study with two upper
limb amputees, showing for the first time that the same brain regions underlie ownership sensations of an artificial
hand in this population. Albeit preliminary, these findings are interesting from both a theoretical as well as a clinical
point of view. From a theoretical perspective, they imply that even years after the amputation, a few seconds of
synchronous visuotactile stimulation are sufficient to activate hand-centered multisensory integration mechanisms.
From a clinical perspective, they show that a very basic sensation of touch from an artificial hand can be obtained
by simple but precisely targeted stimulation of the stump, and suggest that a similar mechanism implemented in
prosthetic hands would greatly facilitate ownership sensations and in turn, acceptance of the prosthesis
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The moving rubber hand illusion revisited: comparing movements and visuotactile stimulation to induce illusory ownership
The rubber hand illusion is a perceptual illusion in which a model hand is experienced as
part of one’s own body. In the present study we directly compared the classical illusion,
based on visuotactile stimulation, with a rubber hand illusion based on active and passive
movements. We examined the question of which combinations of sensory and motor cues
are the most potent in inducing the illusion by subjective ratings and an objective measure
(proprioceptive drift). In particular, we were interested in whether the combination of
afferent and efferent signals in active movements results in the same illusion as in the
purely passive modes. Our results show that the illusion is equally strong in all three cases.
This demonstrates that different combinations of sensory input can lead to a very similar
phenomenological experience and indicates that the illusion can be induced by any combination
of multisensory information
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When passive feels active - delusion-proneness alters self-recognition in the moving rubber hand illusion
Psychotic patients have problems with bodily self-recognition such as the experience of self-produced actions (sense of agency) and the perception of the body as their own (sense of ownership). While it has been shown that such impairments in psychotic patients can be explained by hypersalient processing of external sensory input it has also been suggested that they lack normal efference copy in voluntary action. However, it is not known how problems with motor predictions like efference copy contribute to impaired sense of agency and ownership in psychosis or psychosis-related states. We used a rubber hand illusion based on finger movements and measured sense of agency and ownership to compute a bodily self-recognition score in delusion-proneness (indexed by Peters’ Delusion Inventory - PDI). A group of healthy subjects (n=71) experienced active movements (involving motor predictions) or passive movements (lacking motor predictions). We observed a highly significant correlation between delusion-proneness and self-recognition in the passive conditions, while no such effect was observed in the active conditions. This was seen for both ownership and agency scores. The result suggests that delusion-proneness is associated with hypersalient external input in passive conditions, resulting in an abnormal experience of the illusion. We hypothesize that this effect is not present in the active condition because deficient motor predictions counteract hypersalience in psychosis proneness
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Moving a rubber hand: the sense of ownership and agency in bodily self-recognition
Most of us take for granted that our body is our body. One typically experiences one’s
body as something belonging just to oneself, as something that can only be “me”.
However, this poses a fundamental problem in philosophy and psychology: how do
we know that the body is our own? It has been suggested that two distinct experiences
of our own body help us recognize it as such: the sense of ownership, that is the
experience that a limb is part of one’s body, and the sense of agency, that is the
experience of being able to voluntarily control limb movement. In the present thesis we
introduce a new version of the classical rubber hand illusion that is based on finger
movements instead of stroking and systematically investigate how ownership and
agency contributes to bodily self-recognition.
To induce “the moving rubber hand illusion” participants control the movements of
the index finger of a right wooden model hand in full view by moving their own right
index finger, which is hidden from view. The illusion is quantified subjectively with
visual analogue rating scales and behaviourally as changes in manually indicated
sensed hand position (“proprioceptive drift”). In 9 separate experiments involving a
total of 352 healthy volunteers we first characterized the basic constrains of the illusion.
Secondly, we examined the relationship of ownership and agency. And finally,
investigate a possible relationship between the illusion and individual differences in
delusion proneness (using Peter’s Delusion Inventory).
Our results show that synchronized movements of the model’s index finger and the
participant’s index can trigger a strong illusory feeling of ownership of the model hand
and robust experience of agency. The moving rubber hand illusion is similarly strong as
the classical version, and follows similar temporal, spatial and anatomical rules.
Asynchronous seen and felt finger movements, a too great distance between the real
and model hands (≥27 cm), or the model placed in an anatomically implausible position
abolishes the ownership-illusion.
We also found that ownership and agency can be dissociated. Unlike ownership,
agency can be experienced for the model hand when it is when placed in an
anatomically implausible position. And ownership can be experienced irrespective of
the hand moving actively or passively, so with or without agency. Furthermore only
ownership, but not agency ratings correlate with the proprioceptive drift. Finally, we
observed that delusion prone-individuals tend to give generally higher overall ratings
on agency, when they experience the hand moved passively.
Collectively, these observations advance our understanding of how ownership and
agency contribute to bodily self-recognition. Ownership and agency constitute different
processes: Integration of spatio-temporally congruent signals from moving limbs
determine the sense of ownership and a match of movement intentions and feedback
determines the sense of agency. These results offer new ways to study bodily selfrecognition
both at the behavioural and neural level
Region‐of‐interest analysis approaches in neuroimaging studies of body ownership : An activation likelihood estimation meta‐analysis
How do we feel that we own our body? By manipulating the integration of multisensory signals and creating the illusory experience of owning external body parts and entire bodies, researchers have investigated the neurofunctional correlates of body ownership. Recent attempts to synthesize the neuroimaging literature of body ownership through meta-analysis have shown partly inconsistent results. A large proportion of functional magnetic resonance imaging (fMRI) findings on body ownership include analyses based on regions of interest (ROIs). This approach can produce inflated findings when results are synthesized in meta-analyses. We conducted a systematic search of the fMRI literature of ownership of body parts and entire bodies. Three activation likelihood estimation (ALE) meta-analyses were conducted, testing the impact of including ROI-based findings. When both whole-brain and ROI-based results were included, frontal and posterior parietal multisensory areas were associated with body ownership. When only ROI-based results were included, larger areas of the frontal and posterior parietal cortices and the middle occipital gyrus were associated with body ownership. A whole-brain meta-analysis, excluding ROI-based results, found no significant convergence of activation across the brain. These findings highlight the difficulty of quantitatively synthesizing a neuroimaging field where a large part of the literature is based on findings from ROI-based analyses. We discuss these findings in the light of current practices within this field of research and highlight current problems of meta-analytic approaches of body ownership. We recommend the sharing of unthresholded data as a means to facilitate future meta-analyses of the neuroimaging literature of body ownership.CC BY-NC 4.0First published: 18 November 2021Correspondence: Andreas Kalckert, Department of Cognitive Neuroscience and Philosophy, Institute of Bioscience, University of Skövde, Skövde, Sweden. Email: [email protected]</p