Quantifying body ownership information processing and perceptual bias in the rubber hand illusion

The prediction-confirmation account of the sense of body ownership: Evidence from a rubber hand illusion paradigm

We investigated the contribution of multisensory predictions to body ownership, and beyond, to the integration of body-related signals. Contrary to the prevailing idea, according to which, to be integrated, cues necessarily have to be perceived simultaneously, we instead proposed the prediction-confirmation account. According to this account, a perceived cue can be integrated with a predicted cue as long as both signals are relatively simultaneous. To test this hypothesis, a standard rubber hand illusion (RHI) paradigm was used. In the first part of each trial, the illusion was induced while participants observed the rubber hand being touched with a paintbrush. In the subsequent part of the trial, (i) both rubber hand and the participant's real hand were stroked as before (i.e., visible/synchronous condition), (ii) the rubber hand was not stroke anymore (i.e., visible/tactile-only condition), or (iii) both rubber hand and the participant's real hand were synchronously stroked while the location where the rubber hand was touched was occulted (i.e., occulted/synchronous condition). However, in this latter condition, participants still perceived the approaching movement of the paintbrush. Thus, based on this visual cue, the participants can properly predict the timepoint at which the tactile cue should occur (i.e., visuotactile predictions). Our major finding was that compared with the visible/tactile-only condition, the occulted/synchronous condition did not exhibit a decrease of the RHI as in the visible/synchronous condition. This finding supports the prediction-confirmation account and suggests that this mechanism operates even in the standard version of the RHI.

Neural correlates of phantom motor execution: A functional neuroimaging systematic review and meta-analysis

Phantom motor execution (PME) shows promise as a new treatment for phantom limb pain (PLP) by inducing motor-related analgesia and retraining the pain network activation. However, the current understanding of the neural correlates underlying PME is limited. Databases were systematically searched for multimodal neuroimaging studies to explore the neural correlates of PME. A narrative synthesis (17 studies, n = 328) and coordinate-based meta-analysis were performed to identify activation commonalities. Contrasting PME-vs-REST revealed differential activation of the supplementary motor area (SMA), post-central gyrus, and dorsolateral superior frontal gyrus; while PME-vs-ME revealed differential activation of the right anterior insula, anterior cingulate, left amygdala, and right striatum. Further narrative synthesis revealed a positive correlation between PME-induced brain activity and PLP intensity, and a specific connectivity pattern during PME on the SMA-M1 network compared to ME and motor imagery. Our results suggest that the PME represents a distinct type of motor network activation, partially overlapping with ME and motor imagery activations but with special activation of interoceptive regulation and mood-related regions. Thus, confirming its potential as a therapeutic approach for PLP.

Disrupted sense of agency-related ownership and disownership increase in the Rubber Hand Illusion

Empirical evidence suggests that body ownership and the sense of agency operate as an interactive system correlated with the level of consciousness during tasks involving modifications in body representation. This study sought to elucidate the nature of this association by documenting the verbal manifestations of this interaction. Specifically, the study aimed to reveal the role of a sense of agency in the individual sensitivity to the Rubber Hand Illusion (RHI). The sense of agency was measured through a post hoc interview wherein participants could verbally express their rubber hand ownership and real hand disownership experiences following the RHI examination. The RHI was induced in 49 healthy, right-handed college volunteers, including 28 males (mean age 28.6) and 21 females (mean age 26.6). Three main scores - ownership, disownership, and proprioceptive drift - were defined to measure individual sensitivity to Rubber Hand Illusion. Verbal reports related to the RHI were analyzed utilizing an automated narrative content analysis toolkit which explored the deeper content of words and stories to identify situation-driven cognitive processes, specifically focusing on the rate of sense of agency and other cognitive variables. The findings indicated that a greater disruption in the sense of agency predicts increased sensitivity to the Rubber Hand Illusion. Therefore, individuals with a lower rate sense of agency exhibit increased malleability in body representation when a rubber hand illusion is induced.

Aging, not Parkinson's disease, decreases a recalibration of body ownership caused by vision-respiratory interaction

Introduction

Recalibration of body ownership perception occurs through an integration among multiple modalities. A recent study has shown that respiratory rhythm also causes the recalibration of ownership perception. However, the risk factors influencing the recalibration of ownership perception caused by vision-respiratory interaction remain unclear. In this study, focusing on aging and Parkinson's disease (PD), we examined the effects of those risk factors on the recalibration.

Methods

By applying the rubber hand illusion (RHI), which temporarily alters ownership perception, and using a device that synchronizes the respiratory rhythm with the movement of a mannequin hand, we measured a change in ownership perception in RHI training by vision-respiratory interaction. The changed ownership was compared among the elderly healthy, PD, and young healthy groups.

Results

The results showed no difference in the changed ownership between the elderly healthy and PD groups, while the two groups decreased the change in the ownership perception compared to the young healthy group.

Discussion

The finding suggests that aging, not PD, related to the recalibration of ownership perception by vision-respiratory interaction. An anomaly in body perception due to aging may be associated with a mechanism in which respiratory rhythm affects the adaptation of body representations.

Individual Differences in Bodily Self-Consciousness and Its Neural Basis

Bodily self-consciousness (BSC), a subject of interdisciplinary interest, refers to the awareness of one's bodily states. Previous studies have noted the existence of individual differences in BSC, while neglecting the underlying factors and neural basis of such individual differences. Considering that BSC relied on integration from both internal and external self-relevant information, we here review previous findings on individual differences in BSC through a three-level-self model, which includes interoceptive, exteroceptive, and mental self-processing. The data show that cross-level factors influenced individual differences in BSC, involving internal bodily signal perceptibility, multisensory processing principles, personal traits shaped by environment, and interaction modes that integrate multiple levels of self-processing. Furthermore, in interoceptive processing, regions like the anterior cingulate cortex and insula show correlations with different perceptions of internal sensations. For exteroception, the parietal lobe integrates sensory inputs, coordinating various BSC responses. Mental self-processing modulates differences in BSC through areas like the medial prefrontal cortex. For interactions between multiple levels of self-processing, regions like the intraparietal sulcus involve individual differences in BSC. We propose that diverse experiences of BSC can be attributed to different levels of self-processing, which moderates one's perception of their body. Overall, considering individual differences in BSC is worth amalgamating diverse methodologies for the diagnosis and treatment of some diseases.

Texture congruence modulates perceptual bias but not sensitivity to visuotactile stimulation during the rubber hand illusion

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.

Subcortical contributions to the sense of body ownership

The sense of body ownership (i.e. the feeling that our body or its parts belong to us) plays a key role in bodily self-consciousness and is believed to stem from multisensory integration. Experimental paradigms such as the rubber hand illusion have been developed to allow the controlled manipulation of body ownership in laboratory settings, providing effective tools for investigating malleability in the sense of body ownership and the boundaries that distinguish self from other. Neuroimaging studies of body ownership converge on the involvement of several cortical regions, including the premotor cortex and posterior parietal cortex. However, relatively less attention has been paid to subcortical structures that may also contribute to body ownership perception, such as the cerebellum and putamen. Here, on the basis of neuroimaging and neuropsychological observations, we provide an overview of relevant subcortical regions and consider their potential role in generating and maintaining a sense of ownership over the body. We also suggest novel avenues for future research targeting the role of subcortical regions in making sense of the body as our own.

Revisiting the relationship between illusory hand ownership induced by visuotactile synchrony and cardiac interoceptive accuracy

Multisensory integration plays an important role in the experience of the bodily self. Recently, the relationship between exteroception and interoception has been actively debated. The first evidence was a report that the susceptibility of the sense of ownership over a fake hand (i.e., illusory hand ownership: IHO) in the typical rubber hand illusion is negatively modulated by the accuracy of the heartbeat perception (i.e., cardiac interoceptive accuracy: CIA). If reliable, this would suggest an antagonism between the exteroceptive and interoceptive cues underlying the bodily self. However, some inconsistent data have been reported, raising questions about the robustness of the initial evidence. To investigate this robustness, we estimated the extent of the modulatory effect of CIA on IHO susceptibility by applying Bayesian hierarchical modeling to two independent datasets. Overall, our results did not support that IHO susceptibility is modulated by CIA. The present estimates with high uncertainty cannot exclude the hypothesis that the relationship between IHO susceptibility and CIA is so weak as to be negligible. Further studies with larger sample sizes are needed to reach a conclusion about the extent of the modulatory effect. These findings highlight the lack of robustness of key evidence supporting the "antagonism hypothesis".