Interoception in Parkinson’s disease: linking perception of internal signals to behavioural outcomes

Interoception, the perception and representation of internal bodily signals, has emerged as a crucial dimension in understanding non-motor symptoms of Parkinson’s disease (PD). Beyond the classical motor features, PD is characterised by cognitive, emotional, autonomic, and somatosensory alterations that differ across clinical subtypes, particularly between tremor-dominant (TD) and postural instability gait difficulty (PIGD) phenotypes. Growing evidence indicates that interoceptive dysfunctions may contribute to these non-motor manifestations, including anxiety, depression, apathy, and altered emotional awareness. 
Interestingly, TD patients display reduced interoceptive accuracy and sensibility compared to both PIGD patients and healthy controls. These differences are not explained by general cognitive or temporal estimation deficits, suggesting a specific impairment in bodily signal processing. Such results highlight interoceptive measures as potential behavioural markers for phenotypic differentiation within PD. 
Additionally, interoceptive processing appears to play a key role in the emergence of impulsive compulsive behaviour disorders (ICBDs) in PD, which include impulse control disorders (ICDs) and compulsive behaviours often associated with dopaminergic therapy and altered reward mechanisms. While interoceptive accuracy does not seem to vary with ICD severity, higher impulsivity has been linked to increased interoceptive sensibility and insight, possibly reflecting an exaggerated subjective awareness of bodily states. 
Altogether, these findings illustrate a complex interplay between interoception, emotional regulation, and reward-related neural circuits involving the insula and anterior cingulate cortex. Understanding interoceptive alterations in PD may provide new perspectives for disease subtyping, individualized therapeutic strategies, and the management of non-motor symptoms and behavioral dysregulation through interoception-based approaches.

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