Balancing the "inner" and the "outer" self: interoceptive sensitivity modulates self-other boundaries

Distinguishing self from other is necessary for self-awareness and social interactions. This distinction is thought to depend on multisensory integration dominated by visual feedback. However, self-awareness also relies on the processing of interoceptive signals. We contrasted the exteroceptive and interoceptive models of the self to investigate the hitherto unexplored interaction between the perception of the self from the outside and from within. Multisensory stimulation between self and other was used to induce controlled changes in the representation of one's identity. Interoceptive sensitivity predicted the malleability of self-representations in response to multisensory integration across behavioral, physiological, and introspective responses, suggesting that interoception plays a key modulating role in the self-recognition system. In particular, only participants with low interoceptive sensitivity experienced changes in self-other boundaries in response to multisensory stimulation. These results support the view that interoceptive predictive coding models are used to monitor and assign the sources of sensory input either to the self or to others, as well as support the hypothesis of the insular cortex as a convergence zone in the processing and global representation of the material self given its involvement in both interoceptive feelings, multisensory integration, and self-processing.