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 neuro-degenerative 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. (C) 2016 Elsevier B.V. All rights reserved.