The processing of interoceptive signals in the insular cortex is thought to underlie self-awareness. However, the influence of interoception on visual awareness and the role of the insular cortex in this process remain unclear. Here, we show in a series of experiments that the relative timing of visual stimuli with respect to the heartbeat modulates visual awareness. We used two masking techniques and show that conscious access for visual stimuli synchronous to participants' heartbeat is suppressed compared with the same stimuli presented asynchronously to their heartbeat. Two independent brain imaging experiments using high-resolution fMRI revealed that the insular cortex was sensitive to both visible and invisible cardio-visual stimulation, showing reduced activation for visual stimuli presented synchronously to the heartbeat. Our results show that interoceptive insular processing affects visual awareness, demonstrating the role of the insula in integrating interoceptive and exteroceptive signals and in the processing of conscious signals beyond self-awareness.

Recent research has investigated self-consciousness associated with the multisensory processing of bodily signals (e.g., somatosensory, visual, vestibular signals), a notion referred to as bodily self-consciousness, and these studies have shown that the manipulation of bodily inputs induces changes in bodily self-consciousness such as self-identification. Another line of research has highlighted the importance of signals from the inside of the body (e.g., visceral signals) and proposed that neural representations of internal bodily signals underlie self-consciousness, which to date has been based on philosophical inquiry, clinical case studies, and behavioral studies. Here, we investigated the relationship of bodily self-consciousness with the neural processing of internal bodily signals. By combining electrical neuroimaging, analysis of peripheral physiological signals, and virtual reality technology in humans, we show that transient modulations of neural responses to heartbeats in the posterior cingulate cortex covary with changes in bodily self-consciousness induced by the full-body illusion. Additional analyses excluded that measured basic cardiorespiratory parameters or interoceptive sensitivity traits could account for this finding. These neurophysiological data link experimentally the cortical mapping of the internal body to selfconsciousness.

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Dyspnoea, a subjective experience of breathing discomfort, is a most distressing symptom. It implicates complex cortical networks that partially overlap with those underlying bodily self-consciousness, the experience that the body is one’s own within a given location (self-identification and self-location, respectively). Breathing as an interoceptive signal contributes to bodily self-consciousness: we predicted that inducing experimental dyspnoea would modify or disrupt this contribution. We also predicted that manipulating bodily self-consciousness with respiratory-visual stimulation would possibly attenuate dyspnoea. Twenty-five healthy volunteers were exposed to synchronous and asynchronous respiratory-visual illumination of an avatar during normal breathing and mechanically loaded breathing that elicited dyspnoea. During normal breathing, synchronous respiratory-visual stimulation induced illusory self-identification with the avatar and an illusory location of the subjects’ breathing towards the avatar. This did not occur when respiratory-visual stimulation was performed during dyspnoea-inducing loaded breathing. In this condition, the affective impact of dyspnoea was attenuated by respiratory-visual stimulation, particularly when asynchronous. This study replicates and reinforces previous studies about the integration of interoceptive and exteroceptive signals in the construction of bodily self-consciousness. It confirms the existence of interferences between experimental dyspnoea and cognitive functions. It suggests that respiratory-visual stimulation should be tested as a non-pharmacological approach of dyspnoea treatment.

This study provides Class III evidence that HEVR reduces pain and increases force strength in patients with CRPS.

Exteroceptive bodily signals (including tactile, proprioceptive and visual signals) are important information contributing to self-consciousness. Moreover, prominent theories proposed that visceral signals about internal bodily states are equally or even more important for self-consciousness. Neuroimaging studies have described several brain regions which process signals related to bodily self-consciousness (BSC) based on the integration of exteroceptive signals (e.g. premotor cortex, angular gyrus, supramarginal gyrus and extrastriate body area), and that another brain region, the insula/operculum which is involved in interoception and interoceptive awareness, processes signals critical for self-awareness. Providing evidence for the integration of exteroceptive and interoceptive bodily signals, recent behavioral experiments have demonstrated that the manipulation of interoceptive (e.g. cardiac) signals, coupled with exteroceptive (e.g. visual) signals, also modulates BSC. Does this integration occur within or outside the structures described above? To this end, we adapted a recently designed protocol that uses cardio-visual stimulation to induce altered states of BSC to fMRI. Additionally, we measured neural activity in a classical interoceptive task. We found six brain regions (bilateral Rolandic operculum, bilateral supramarginal gyrus, right frontal inferior operculum and left temporal superior gyrus) that were activated differently during the interoception task as opposed to a control task. The brain regions which showed the highest selectivity for BSC based on our cardio-visual manipulation were found in the bilateral Rolandic operculum. Given our findings, we propose that the Rolandic operculum processes integrated exteroceptive-interoceptive signals that are necessary for interoceptive awareness as well as BSC.

Previous studies investigated bodily self‐consciousness (BSC) by experimentally exposing subjects to multisensory conflicts (i.e., visuo‐tactile, audio‐tactile, visuo‐cardiac) in virtual reality (VR) that involve the participant's torso in a paradigm known as the full‐body illusion (FBI). Using a modified FBI paradigm, we found that synchrony of visuo‐respiratory stimulation (i.e., a flashing outline surrounding an avatar in VR; the flash intensity depending on breathing), is also able to modulate BSC by increasing self‐location and breathing agency toward the virtual body. Our aim was to investigate such visuo‐respiratory effects and determine whether respiratory motor commands contributes to BSC, using non‐invasive mechanical ventilation (i.e., machine‐delivered breathing). Seventeen healthy participants took part in a visuo‐respiratory FBI paradigm and performed the FBI during two breathing conditions: (a) “active breathing” (i.e., participants actively initiate machine‐delivered breaths) and (b) “passive breathing” (i.e., breaths’ timing was determined by the machine). Respiration rate, tidal volume, and their variability were recorded. In line with previous results, participants experienced subjective changes in self‐location, breathing agency, and self‐identification toward the avatar's body, when presented with synchronous visuo‐respiratory stimulation. Moreover, drift in self‐location was reduced and tidal volume variability were increased by asynchronous visuo‐respiratory stimulations. Such effects were not modulated by breathing control manipulations. Our results extend previous FBI findings showing that visuo‐respiratory stimulation affects BSC, independently from breathing motor command initiation. Also, variability of respiratory parameters was influenced by visuo‐respiratory feedback and might reduce breathing discomfort. Further exploration of such findings might inform the development of respiratory therapeutic tools using VR in patients.