Disturbances of Interoception in Schizophrenia - Focus on Neuroimaging

: The current paper presents the most recent theoretical understanding of interoception (INTC) in light of the predictive processing framework and the Embodied Predictive Interoceptive Coding model and reviews recent experimental data on different interoceptive disturbances in schizophrenia (SCZ) such as lower interoceptive accuracy, nociceptive dysfunction reflected by reduced pain sensitivity, disturbed thermoregulation, impaired gastrointestinal regulation, cardiovascular and respiratory dysfunction, and immune disturbances. The immense clinical implications of these disturbances are discussed in the context of the high rates of morbidity and mortality in SCZ related to suicide and cardiac death. Next, the potential of INTC-related treatments is reviewed, and conclusions are made on the evidence for the use of vagus nerve stimulation, mindfulness-based interventions, and exercise therapy. The neuroimaging perspective is given in a brief account of the INTC-related findings in healthy individuals suggesting the right anterior insula and anterior cingulate cortex as key brain areas for interoceptive awareness, accuracy, and sensibility, by supporting higher-order representation and integration of visceral, and somatosensory interoception with exteroceptive information. In SCZ, on the other hand, neuroimaging research on specific interoceptive abilities is lacking but indirect evidence points to disrupted activation of major INTC network hubs. There is converging evidence of changes in these hubs in terms of both structure and function (volume reductions, aberrant activation, and connectivity). This narrative review identifies several gaps in contemporary INTC-related research in SCZ that need to be addressed in future experimental and clinical studies to elucidate the exact nature of the disturbances of interoceptive abilities in modalities other than cardioception; the interactions between different interoceptive modalities; the association between interoceptive abilities and other mental functions (such as emotion recognition and regulation, decision making, learning, memory, etc.); the efficacy of nonpharmacological and pharmacological INTC-based interventions; and the relation of disturbed interoceptive abilities with brain structure and function.