Crossmodal bias of visual input on pain perception and pain-induced beta activity

article i nfo In our environment, acute pain is often accompanied by input from other sensory modalities, like visual stimuli, which can facilitate pain processing. To date, it is not well understood how these inputs influence the perception and processing of pain. Previous studies on integrative processing between sensory modalities other than pain haveshownthatmultisensoryresponse gains are strongest whentheconstituent unimodalstimuli are minimal- ly effective in evoking responses. This finding has been termed the principle of inverse effectiveness (IE). In this high-densityelectroencephalographystudy,weinvestigated theinfluence of Gaborpatchesoflowand high con- trast levels on the perception and processing of spatially and temporally aligned painful electrical stimuli of low and high intensities. Subjective pain ratings, event-related potentials (ERPs) and oscillatory responses served as dependent measures. In line with the principle of IE, stronger crossmodal biasing effects of visual input on sub- jective pain ratings were found for low compared to high intensity painful stimuli. This effect was paralleled by stronger bimodal interactions in right-central ERPs (150-200 ms) for low compared to high intensity pain stim- uli.Moreover,anenhancedsuppressionofmedio-centralbeta-bandactivity (12-24 Hz,200-400 ms)wasfound for low compared to high intensity pain stimuli. Our findings possibly reflect a facilitation of stimulus processing that serves to enhance response readiness of the sensorimotor system following painful stimulation. Taken to- gether, our study demonstrates that multisensory processing between visual and painful stimuli follows the principle of IE and suggests a role for beta-band oscillations in the crossmodal modulation of pain.