Increased somatic sensations are associated with reduced limb ownership.

OBJECTIVE Medically unexplained symptoms (MUS) are increasingly being thought of as resulting from dysfunctional modulation of interoceptive sensory signals by top-down cognitive processes. The current study investigated whether individuals with a tendency toward MUS would be more susceptible to visual illusions that suggest tactile sensation on the skin in the absence of any actual somatosensory input. METHOD Participants viewed real-time-mediated reality video images of their own hand, either un-manipulated or digitally altered to display moving pixelated 'static' effect, the crawling skin illusion. The strength of various physical sensations during each condition were rated on a numeric scale and compared to standard measures of somatoform dissociation (Somatoform Dissociation Questionnaire 20). RESULTS Participants reporting a higher degree of somatoform dissociation were found to be more susceptible to somatic sensations across all conditions. Interestingly, participants who reported more visually induced somatosensory sensations also felt less ownership over their digitally presented hands. CONCLUSION These findings support the proposed link between MUS and disturbances in body representation, and suggest that an over-reliance on top-down knowledge may interfere with current sensory inputs, contributing to symptom formation and maintenance in susceptible individuals.