Perceiving Itch-Related Stimuli: Differences Between Unisensory and Multisensory Perception
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Background: Itch sensations can be triggered in healthy individuals when watching someone else scratching. However, in our multisensory environment, itch-related stimuli can be processed differently as using multiple senses improves the perception of these stimuli. Studies investigating the top-down effect of itch-related stimuli in a multisensory context are lacking. Here we investigate experimentally whether multisensory perception of itch-related stimuli, compared to unisensory perception, induces stronger itch sensations in healthy individuals. Further, we examine which body parts and side of the body participants perceived as itchy. Method: Thirty female volunteers were presented with video- and sound clips depicting someone scratching. Participants were then asked to rate their level of perceived itch, and to indicate which body parts they perceived as itchy. The experimenter obtained which exact side of the body was perceived as itchy. Results: Participants did not only perceive a higher level of itch but they even engaged more in spontaneous scratching behavior when we presented itch-related stimuli, compared to non-itch related stimuli. However, compared to unisensory perception, multisensory perception of itch-related stimuli did not induce stronger itch sensations. Results further show that participants tended to perceive their face and both sides of their body as itchy. Conclusions: Perceiving itch-related stimuli in their isolated modality seems effective enough to induce itch sensations that are strong as when those stimuli would be perceived with multiple senses. Our findings also suggest that instead of the actual scratching behavior, observed sensations are transmitted which can indicate that itch is not sensory mapped.