Multisensory body representation in autoimmune diseases

[Between the normal and the pathological: The concept of pre-disease applied to systemic autoimmune rheumatic diseases]

The incidence of systemic autoimmune diseases is constantly rising. They are chronic diseases requiring prolonged treatment, with considerable psychosocial impact. While attention to the promising results obtained with CAR-T cells in refractory patients is justified, it seems important not to overlook the opportunities for prevention based on the identification of a pre-disease state. After clarifying the various stages that make up this pre-disease state, using the prototypical example of systemic lupus erythematosus, we will apply a transdisciplinary and transpathological approach to describe comparatively recent data obtained for other systemic autoimmune diseases (rheumatoid arthritis, Sjögren's syndrome and systemic scleroderma). We will then discuss the practical implications of this new paradigm in the typical consultation of a potentially "pre-sick" individual, and on the prospects opened up by this new paradigm in care and research.

Body Evaluation and Body Ownership in Patients with Inflammatory Bowel Disease: the Role of Interoceptive Sensibility and Childhood Maltreatment

OBJECTIVE

Inflammatory bowel diseases (IBD) are accompanied by symptoms that can vastly affect patients' representations of their bodies. The aim of this study was to investigate alterations in body evaluation and body ownership in IBD and their link to interoceptive sensibility, gastrointestinal-specific anxiety, and history of childhood maltreatment.

METHODS

Body evaluation and ownership was assessed in 41 clinically remitted patients with IBD and 44 healthy controls (HC) using a topographical self-report method. Interoceptive sensibility, gastrointestinal-specific anxiety and a history of childhood maltreatment were assessed via self-report questionnaires.

RESULTS

Patients reporting higher interoceptive sensibility perceived their bodies in a more positive manner. Higher gastrointestinal-specific anxiety was linked to a more negative body evaluation particularly of the abdomen in patients with IBD. Childhood maltreatment severity strengthened the positive association between interoceptive sensibility and body ownership only in those patients reporting higher trauma load.

CONCLUSION

Altered body representations of areas associated with abdominal pain are linked to higher symptom-specific anxiety and lower levels of interoceptive sensibility in IBD. Particularly in patients with a history of childhood maltreatment, higher levels of interoceptive sensibility might have a beneficial effect on the patients' sense of body ownership.

Understanding the neural bases of bodily self-consciousness: recent achievements and main challenges

The last two decades have seen a surge of interest in the mechanisms underpinning bodily self-consciousness (BSC). Studies showed that BSC relies on several bodily experiences (i.e., self-location, body ownership, agency, first-person perspective) and multisensory integration. The aim of this literature review is to summarize new insights and novel developments into the understanding of the neural bases of BSC, such as the contribution of the interoceptive signals to the neural mechanisms of BSC, and the overlap with the neural bases of conscious experience in general and of higher-level forms of self (i.e., the cognitive self). We also identify the main challenges and propose future perspectives that need to be conducted to progress into the understanding of the neural mechanisms of BSC. In particular, we point the lack of crosstalk and cross-fertilization between subdisciplines of integrative neuroscience to better understand BSC, especially the lack of research in animal models to decipher the neural networks and systems of neurotransmitters underpinning BSC. We highlight the need for more causal evidence that specific brain areas are instrumental in generating BSC and the need for studies tapping into interindividual differences in the phenomenal experience of BSC and their underlying mechanisms.

Temporal dynamics of the Rubber Hand Illusion

It is widely accepted that the representation of the body is not fixed and immutable, but rather flexible and constantly updated based on a continuous stream of multisensory information. This mechanism can be very useful to adapt to several situations, but it would not be adaptive if the body representation was too malleable or if it wasn't capable of restoring its integrity after a transient modification. Here we used the Rubber Hand Illusion (RHI) to investigate how quickly the body representation can be modified. Previous studies have investigated the timing of the onset and offset of the illusion, however, they did not assess a fine temporal resolution. Here, we used a potentiometer to record a moment-by-moment rating of the feeling of owning the RH for two minutes during the visuo-tactile stimulation and two minutes following the stimulation. Our results suggest that the feeling of Ownership is already established during the first 19 s of stimulation then it continues to grow, but at a much slower pace. The feeling of Ownership disappears within 66 s from the end of the stimulation. This work sheds new light on the temporal dynamics of the RHI and the malleability of the body self-consciousness.

The sensorimotor theory of pathological pain revisited

Harris (1999) proposed that pain can arise in the absence of tissue damage because changes in the cortical representation of the painful body part lead to incongruences between motor intention and sensory feedback. This idea, subsequently termed the sensorimotor theory of pain, has formed the basis for novel treatments for pathological pain. Here we review the evidence that people with pathological pain have changes to processes contributing to sensorimotor function: motor function, sensory feedback, cognitive representations of the body and its surrounding space, multisensory processing, and sensorimotor integration. Changes to sensorimotor processing are most evident in the form of motor deficits, sensory changes, and body representations distortions, and for Complex Regional Pain Syndrome (CRPS), fibromyalgia, and low back pain. Many sensorimotor changes are related to cortical processing, pain, and other clinical characteristics. However, there is very limited evidence that changes in sensorimotor processing actually lead to pain. We therefore propose that the theory is more appropriate for understanding why pain persists rather than how it arises.

Virtual reality in neurorehabilitation: a review of its effects on multiple cognitive domains

INTRODUCTION

Neurological diseases frequently cause adult-onset disability and have increased the demand for rehabilitative interventions. Neurorehabilitation has been progressively relying on computer-assisted programs and, more recently, on virtual reality (VR). Current reviews explore VR-based neurorehabilitation for assessing and treating the most common neurological pathologies. However, none of them explored specifically the impact of VR on multiple cognitive domains.

AREAS COVERED

The present work is a review of 6 years of literature (2015-2020) on VR in neurorehabilitation with the purpose of analyzing its effects on memory, attention, executive functions, language, and visuospatial ability.

EXPERT OPINION

Our review suggests that VR-based neurorehabilitation showed encouraging results for executive functions and visuospatial abilities particularly for both acute and neurodegenerative conditions. Conversely, memory, and attention outcomes are conflicting, and language did not show significant improvements following VR-based rehabilitation. Within five years, it is plausible that VR-based intervention would be provided in standalone and mobile-based platforms that won't need a PC to work, with reduced latency and improved user interaction.

Neuroscience of Virtual Reality: From Virtual Exposure to Embodied Medicine

Is virtual reality (VR) already a reality in behavioral health? To answer this question, a meta-review was conducted to assess the meta-analyses and systematic and narrative reviews published in this field in the last twenty-two months. Twenty-five different articles demonstrated the clinical potential of this technology in both the diagnosis and the treatment of mental health disorders: VR compares favorably to existing treatments in anxiety disorders, eating and weight disorders, and pain management, with long-term effects that generalize to the real world. But why is VR so effective? Here, the following answer is suggested: VR shares with the brain the same basic mechanism: embodied simulations. According to neuroscience, to regulate and control the body in the world effectively, the brain creates an embodied simulation of the body in the world used to represent and predict actions, concepts, and emotions. VR works in a similar way: the VR experience tries to predict the sensory consequences of an individual's movements, providing to him/her the same scene he/she will see in the real world. To achieve this, the VR system, like the brain, maintains a model (simulation) of the body and the space around it. If the presence in the body is the outcome of different embodied simulations, concepts are embodied simulations, and VR is an embodied technology, this suggests a new clinical approach discussed in this article: the possibility of altering the experience of the body and facilitating cognitive modeling/change by designing targeted virtual environments able to simulate both the external and the internal world/body.

Multisensory integration, body representation and hyperactivity of the immune system

Multisensory stimuli are integrated over a delimited window of temporal asynchronies. This window is highly variable across individuals, but the origins of this variability are still not clear. We hypothesized that immune system functioning could partially account for this variability. In two experiments, we investigated the relationship between key aspects of multisensory integration in allergic participants and healthy controls. First, we tested the temporal constraint of multisensory integration, as measured by the temporal binding window. Second, we tested multisensory body representation, as indexed by the Rubber Hand Illusion (RHI). Results showed that allergic participants have a narrower temporal binding window and are less susceptible to the RHI than healthy controls. Overall, we provide evidence linking multisensory integration processes and the activity of the immune system. The present findings are discussed within the context of the effect of immune molecules on the brain mechanisms enabling multisensory integration and multisensory body representation.

On the relation between body ownership and sense of agency: A link at the level of sensory-related signals

The relation between sense of body ownership and sense of agency is still highly debated. Here we investigated in a large sample of healthy participants the associations between several implicit and explicit indexes of the two senses. Specifically, we examined the correlations between proprioceptive shift (implicit measure) and questionnaire on the subjective experience of ownership (explicit measure) within the rubber hand illusion paradigm (body ownership), and intentional binding (implicit measure), attenuation of the intensity of auditory outcomes of actions (implicit measure) and questionnaire on the subjective experience of authorship (explicit measure) within the Libet's clock paradigm (sense of agency). Our results showed that proprioceptive shift was positively correlated with the attenuation of auditory outcomes. No significant correlations were found between the explicit measures of the two senses. We argue that the individual spatiotemporal constraints subserving the integration of sensory-related signals (implicit signature) would be common to both senses, whereas their subjective experience (explicit signature) would rely on additional processes specific for any given sense.

The neuroscience of body memory: From the self through the space to the others

Our experience of the body is not direct; rather, it is mediated by perceptual information, influenced by internal information, and recalibrated through stored implicit and explicit body representation (body memory). This paper presents an overview of the current investigations related to body memory by bringing together recent studies from neuropsychology, neuroscience, and evolutionary and cognitive psychology. To do so, in the paper, I explore the origin of representations of human body to elucidate their developmental process and, in particular, their relationship with more explicit concepts of self. First, it is suggested that our bodily experience is constructed from early development through the continuous integration of sensory and cultural data from six different representations of the body, i.e., the Sentient Body (Minimal Selfhood), the Spatial Body (Self Location), the Active Body (Agency), the Personal Body (Whole Body Ownership - Me); the Objectified Body (Objectified Self - Mine), and the Social Body (Body Satisfaction - Ideal Me). Then, it is suggested that these six representations can be combined in a coherent supramodal representation, i.e. the "body matrix", through a predictive, multisensory processing activated by central, top-down, attentional processes. From an evolutionary perspective, the main goal of the body matrix is to allow the self to protect and extend its boundaries at both the homeostatic and psychological levels. From one perspective, the self extends its boundaries (peripersonal space) through the enactment and recognition of motor schemas. From another perspective, the body matrix, by defining the boundaries of the body, also defines where the self is present, i.e., in the body that is processed by the body matrix as the most likely to be its one, and in the space surrounding it. In the paper I also introduce and discuss the concept of "embodied medicine": the use of advanced technology for altering the body matrix with the goal of improving our health and well-being.

Salivary Oxytocin Concentration Associates with the Subjective Feeling of Body Ownership during the Rubber Hand Illusion

Oxytocin is a hormone of the posterior pituitary that promotes lactation, maternal bonding, and birth. Recent studies have shown that oxytocin may modulate social recognition in both sexes, and thus it may be related to empathy. Brain regions that are associated with social recognition and empathy (e.g., the insular cortex) are activated in the rubber hand illusion (RHI), which involves illusory ownership of a rubber hand caused by brush strokes applied synchronously to both a rubber hand and one of the participant's hand, which is hidden from view. It is intriguing to examine whether oxytocin modulates plastic changes in body representation, such as the changes occurring in the RHI. In the present study, we investigated the relationship between salivary oxytocin concentration and the feeling of rubber hand ownership. Brush strokes were applied synchronously or asynchronously to the participant's hand and a rubber hand on different days. Salivary oxytocin was measured before and after the behavioral tasks. We found that participants who had high concentrations of salivary oxytocin tended to feel strong ownership of the rubber hand. We also found that the participants with a high autism spectrum quotient (AQ) score who particularly felt difficulties in social skills and communications tended to feel weak rubber hand ownership. We observed that illusory body ownership was closely linked to social communications and a related neuroendocrine basis. The results of the present study suggest that an individual's salivary oxytocin concentration can predict the extent to which the individual experiences the RHI; furthermore, oxytocin might modulate the sensation of body ownership.

Embodied Medicine: Mens Sana in Corpore Virtuale Sano

Progress in medical science and technology drastically improved physicians’ ability to interact with patient’s physical body. Nevertheless, medicine still addresses the human body from a Hippocratic point of view, considering the organism and its processes just as a matter of mechanics and fluids. However, the interaction between the cognitive neuroscience of bodily self-consciousness (BSC), fundamentally rooted in the integration of multisensory bodily inputs, with virtual reality (VR), haptic technologies and robotics is giving a new meaning to the classic Juvenal’s latin dictum “Mens sana in corpore sano” (a healthy mind in a healthy body). This vision provides the basis for a new research field, “Embodied Medicine”: the use of advanced technologies for altering the experience of being in a body with the goal of improving health and well-being. Up to now, most of the research efforts in the field have been focused upon how external bodily information is processed and integrated. Despite the important results, we believe that existing bodily illusions still need to be improved to enhance their capability to effectively correct pathological dysfunctions. First, they do not follow the suggestions provided by the free-energy and predictive coding approaches. More, they lacked to consider a peculiar feature of the human body, the multisensory integration of internal inputs (interoceptive, proprioceptive and vestibular) that constitute our inner body dimension. So, a future challenge is the integration of simulation/stimulation technologies also able to measure and modulate this internal/inner experience of the body. Finally, we also proposed the concept of “Sonoception” as an extension of this approach. The core idea is to exploit recent technological advances in the acoustic field to use sound and vibrations to modify the internal/inner body experience.

Altered multisensory temporal integration in obesity

Eating is a multisensory behavior. The act of placing food in the mouth provides us with a variety of sensory information, including gustatory, olfactory, somatosensory, visual, and auditory. Evidence suggests altered eating behavior in obesity. Nonetheless, multisensory integration in obesity has been scantily investigated so far. Starting from this gap in the literature, we seek to provide the first comprehensive investigation of multisensory integration in obesity. Twenty male obese participants and twenty male healthy-weight participants took part in the study aimed at describing the multisensory temporal binding window (TBW). The TBW is defined as the range of stimulus onset asynchrony in which multiple sensory inputs have a high probability of being integrated. To investigate possible multisensory temporal processing deficits in obesity, we investigated performance in two multisensory audiovisual temporal tasks, namely simultaneity judgment and temporal order judgment. Results showed a wider TBW in obese participants as compared to healthy-weight controls. This holds true for both the simultaneity judgment and the temporal order judgment tasks. An explanatory hypothesis would regard the effect of metabolic alterations and low-grade inflammatory state, clinically observed in obesity, on the temporal organization of brain ongoing activity, which one of the neural mechanisms enabling multisensory integration.