In a series of three studies, Dr Marco Solca and colleagues investigated for the first time interoception and its neurophysiological correlates in patients with complex regional pain syndrome (CRPS). Their behavioral and electrophysiological findings demonstrate an impaired ability in patients suffering from CRPS in correctly detecting and processing internal bodily states. In line with earlier work showing that reduced interoception and heartbeat evoked potentials in particular are objective markers of altered body perception in depressed patients, the authors argue that the altered sensory processing observed for interoceptive cardiac signals contributes to the distortion of own body representation in CRPS patients.
Abstract Whereas impaired multisensory processing of bodily stimuli and distorted body representation are wellestablished in various chronic pain disorders, such research has focused on exteroceptive bodily cues andneglected bodily signals from the inside of the body (or interoceptive signals). Extending existing basic andclinical research, we investigated for the first time interoception and its neurophysiological correlates in patients with complex regional pain syndrome (CRPS). In three different experiments, including a total of 36 patients with CRPS and 42 aged-gender matched healthy controls, we measured interoceptive sensitivity (heart beat counting task, HBC) and neural responses to heartbeats (heartbeat evoked potentials, HEPs). As hypothesized, we observed reduced sensitivity in perceiving interoceptive bodily stimuli, i.e. their heartbeat, in two independent samples of CRPS patients (studies 1 and 2). Moreover, the cortical processing of their heartbeat, i.e. the HEP, was reduced compared to controls (study 3) and reduced interoceptive sensitivity and HEPs were related to CRPS patients’ motor impairment and pain duration. By providing consistent evidence for impaired processing of interoceptive bodily cues in CRPS, this study shows that the perceptual changes occurring in chronic pain include signals originating from the visceral organs, suggesting changes in the neural body representation, that includes next to exteroceptive, also interoceptive bodily signals. By showing that impaired interoceptive processing is associated with clinical symptoms, our findings also encourage the use of interoceptive-related information in future rehabilitation for chronic pain.