Increased somatic sensations are associated with reduced limb ownership

Distinct neural signatures of multimodal resizing illusions

Illusory body resizing typically uses multisensory integration to change the perceived size of a body part. Previous studies associate these multisensory body illusions with frontal theta oscillations and parietal gamma oscillations for dis-integration and integration of multisensory signals, respectively. However, recent studies also support illusory changes of embodiment from unimodal visual stimuli. This preregistered study (N = 48) investigated differences between multisensory visuo-tactile and unimodal visual resizing illusions using EEG, to gain a more comprehensive understanding of the neural underpinnings of resizing illusions in a healthy population. We hypothesised (1) stronger illusion in multisensory compared to unimodal, and unimodal compared to incongruent (dis-integration) conditions, (2) greater parietal gamma during multisensory compared to unimodal, and (3) greater frontal theta during incongruent compared to baseline conditions. Subjective Illusory results partially support Hypothesis 1, showing a stronger illusion in multisensory compared to unimodal conditions, but finding no significant difference comparing unimodal to incongruent conditions. Results partially supported EEG hypotheses, finding increased parietal gamma activity comparing multisensory to unimodal visual conditions, happening at a later stage of the illusion when compared to previous rubber hand illusion EEG findings, whilst also finding increased parietal theta activity when comparing incongruent to non-illusion conditions. While results demonstrated that only 27% of participants experienced the stretching illusion with unimodal visual stimuli compared to 73% of participants experiencing the stretching illusion in the multisensory condition, further analysis suggested that those who experience visual-only illusions exhibit a different neural signature to those who do not, with activity focussed around frontal and parietal regions early on in the illusory manipulation, compared to activity focussed more over parietal regions and at a later point in the illusory manipulation for the full sample of participants. Our results replicate previous subjective experience findings and support the importance of multisensory integration for illusory changes in perceived body size, whilst adding to our understanding of the temporal onset of multisensory integration within resizing illusions, differing from that of rubber hand illusions.

Cancer driver mutations in endometriosis: Variations on the major theme of fibrogenesis

BACKGROUND

One recent study reports cancer driver mutations in deep endometriosis, but its biological/clinical significance remains unclear. Since the natural history of endometriosis is essentially gradual progression toward fibrosis, it is thus hypothesized that the six driver genes reported to be mutated in endometriosis (the RP set) may play important roles in fibrogenesis but not necessarily malignant transformation.

METHODS

Extensive PubMed search to see whether RP and another set of driver genes not yet reported (NR) to be mutated in endometriosis have any roles in fibrogenesis. All studies reporting on the role of fibrogenesis of the genes in both RP and NR sets were retrieved and evaluated in this review.

RESULTS

All six RP genes were involved in various aspects of fibrogenesis as compared with only three NR genes. These nine genes can be anchored in networks linking with their upstream and downstream genes that are known to be aberrantly expressed in endometriosis, piecing together seemingly unrelated findings.

CONCLUSIONS

Given that somatic driver mutations can and do occur frequently in physiologically normal tissues, it is argued that these mutations in endometriosis are not necessarily synonymous with malignancy or premalignancy, but the result of enormous pressure for fibrogenesis.

An investigation of contextual factors in the application of multisensory illusions for analgesia in hand osteoarthritis

Objective

Emerging evidence suggests that multisensory illusions can modulate pain and can lead to changes in body perception. The aim of this study was to investigate whether contextual factors could explain the analgesic effects of multisensory body illusions on pain and body perception in people with hand OA (HOA).

Methods

In a crossover study, 28 individuals with painful HOA viewed their most affected hand in and outside of a real-time mediated reality system, with illusory stretching of the hand and changes in sensory input. The outcome measures were pain ratings, pressure pain thresholds, hand function and the subjective experience of the illusion.

Results

Stretching the hand both inside and outside the virtual environment led to a reduction in subjective pain ratings (all P < 0.05). Virtual stretching led to changes in body perception (P < 0.05) with no changes in pressure pain threshold (all P > 0.05). Higher pain at baseline predicted susceptibility to the stretch illusion and mean susceptibility ratings were greatest after the stretch illusion.

Conclusion

The current study highlights the importance of the context in which pain occurs and in which potential treatments may be applied. In this case, virtual and physical stretching modulated pain, but not viewing the hand alone. The research opens important implications for future research, including the use of contextual control conditions and the development of visual feedback interventions for a range of similarly visible chronic conditions for which pain, body image disturbances and body dissatisfaction may be apparent.

Visual perception of the arm manipulates the experienced pleasantness of touch

Touch, such as a caress, can be interpreted as very pleasant. The emotional valence assigned to touch is likely related to certain bottom-up factors, such as optimal activation of C-tactile (CT) afferents. It is however unclear if besides somatosensory input, contextual factors related to the own body also play a role in the perceived pleasantness of touch. To test this, we manipulated visual appearance of the participant’s arm (veridical vision, no vision, pixelated moving statistic projected onto the arm (i.e. crawling skin)). We used slow velocity stroking (CT optimal stroking) with a soft brush to induce pleasant touch, and fast velocity stroking as a control condition. After each visual condition we asked participants (N = 23) to rate the emotional valence of the stroking they felt. After slow velocity stroking ratings on perceived pleasantness (but not on perceived unpleasantness) were modulated by visual condition, with veridical vision of the arm resulting in higher pleasantness ratings than both no vision and pixelated vision. We conclude that contextual processes affect the perceived pleasantness of touch. These findings shed a new light on the underlying mechanisms of how humans experience pleasant touch and show that pleasant touch not solely dependents on bottom up information.

Interoception, contemplative practice, and health

Interoception can be broadly defined as the sense of signals originating within the body. As such, interoception is critical for our sense of embodiment, motivation, and well-being. And yet, despite its importance, interoception remains poorly understood within modern science. This paper reviews interdisciplinary perspectives on interoception, with the goal of presenting a unified perspective from diverse fields such as neuroscience, clinical practice, and contemplative studies. It is hoped that this integrative effort will advance our understanding of how interoception determines well-being, and identify the central challenges to such understanding. To this end, we introduce an expanded taxonomy of interoceptive processes, arguing that many of these processes can be understood through an emerging predictive coding model for mind–body integration. The model, which describes the tension between expected and felt body sensation, parallels contemplative theories, and implicates interoception in a variety of affective and psychosomatic disorders. We conclude that maladaptive construal of bodily sensations may lie at the heart of many contemporary maladies, and that contemplative practices may attenuate these interpretative biases, restoring a person’s sense of presence and agency in the world.