Objectives/Aims Altered interoception may be a core pathophysiological mechanism in functional neurological disorder (FND). However, there have been inconsistent findings from interoceptive accuracy paradigms, with several studies reporting no significant group differences in comparisons to controls when tested at rest/baseline. This is contrary to evidence for alterations in other interoceptive dimensions including awareness (metacognitive evaluation of interoceptive accuracy) and sensibility (self- reported sensitivity to bodily sensations) in this population. We aimed to measure interoception across several dimensions, with the prediction that individuals with FND would show reduced accuracy, awareness, and sensibility compared to controls.
Methods Individuals with FND (n=17, 13F:4M, 10 motor symptoms, 7 motor/seizures) and healthy controls (HC, n=17, 13F:4M) completed measures of interoceptive accuracy and awareness (modified heartbeat tracking task [HTT]) and a time estimation task (TET). Participants also completed a validated scale of interoceptive sensibility (Multidimensional Assessment of Interoceptive Awareness-2, MAIA-2).
Results The groups were matched for age (p=.51), sex (p=1.00), and body mass index (p=.19). FND and HC groups did not differ in interoceptive accuracy (p=1.00) or awareness (p=.99), although the FND group displayed lower scores on the ‘Not- Distracting’ (p<.001, g=1.42) and ‘Trusting’ (p=.005, g=1.17) subscales of the MAIA-2, relative to controls. There was no relationship in either group between HTT and TET scores. There was a significant positive relationship between HTT accuracy and awareness (confidence) in the control group (r=.61, p=.016) but not in the FND group (r=.11, p=.69). Exploratory correlations revealed a significant positive relationship between interoceptive awareness and the ‘Self-Regulation’ subscale of the MAIA-2 in the FND group (r=.77, p=.002).
Conclusions Individuals with FND did not differ from HCs on interoceptive accuracy or awareness, measured at rest. The lower levels of ‘Not-Distracting’ and ‘Trusting’ seen in this FND sample replicated our previous study, suggesting that there may be a separation between trait and state interoceptive awareness in FND, reinforcing the need for interoception to be considered within a multidimensional framework. The lack of relationship between interoceptive accuracy and awareness in the FND group also implies that there may be a disconnect between actual performance and subjective confidence. Our future work will explore the possibility that interoceptive impairments in FND may be state dependent, measuring these interoceptive domains with other paradigms, in larger samples, compared to both healthy and clinical controls.
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