Know thyself: Exploring interoceptive sensitivity in Parkinson's disease

Background Although Parkinson's disease (PD) is defined by its motor symptoms, it is now well recognised that cognitive, affective and emotion domains are also impaired. The pathophysiology of these disabling non-motor symptoms (NMS) remains unclear; recently the involvement of limbic areas, including the insula, in the neurodegenerative process has been suggested to have a key role. These areas, and the insula in particular, are also been suggested as key regions for interoception; interoceptive sensitivity (IS) is a measure of the accuracy of perception of sensations from inside the body related to the function of internal organs. Objectives To evaluate IS in PD patients by means of a well-established task: The heartbeat perception task. Moreover, we evaluated possible correlations between IS and psychological, affective and disease-related characteristics as well as fatigue perception in PD patients. Methods Twenty PD patients and 20 healthy subjects (HS) were included and underwent the heartbeat perception task. An extensive evaluation of motor, non-motor, affective and emotion domains was carried out. Results PD patients showed lower IS than HS (0.58 ± 0.2 vs 0.72 ± 0.1; p = 0.04). PD reported higher scores in scales assessing depression (Hamilton depression scale: 8.7 ± 5.8 vs 6.2 ± 7.5; p = 0.04); anhedonia (Snaith-Hamilton Pleasure Scale: 26.8 ± 9.7 vs 15.4 ± 2.9; p = <0.001) and apathy (Apathy Evaluation Scale: 35.8 ± 8.6 vs 27.8 ± 6.8; p = 0.008). No significant correlations were detected between IS and motor, non-motor, affective and emotion symptoms. Conclusions PD patients have reduced interoceptive sensitivity. Future studies are encouraged to evaluate the importance of interoception in understanding the pathophysiology of affective/emotional symptoms in PD.