Attentional selection of location and modality in touch and pain: an ERP investigation of crossmodal and intermodal effects

The effect of spatial attention on tactile and nociceptive stimuli has been well documented. However, most studies have assessed the effect of attention on either one or the other modality, leaving the influence of crossmodal and intermodal attention on pain and touch largely unexplored. To address this issue, we asked participants to complete an attention task in which both the task-relevant location (left vs. right hand) and the task-relevant modality (pain vs. touch) were simultaneously cued on a trial-by-trial basis. Participants were instructed to respond vocally to targets delivered at the cued location in the cued modality, while ignoring uncued targets and all non-target stimuli. Modulatory effects of spatial attention on ERPs elicited by non-targets impacted sensory specific (P100, N140) as well as longer latency (Nd) components in both modalities. Results showed that effects of spatial attention on the cued modality were similar across touch and pain, albeit stronger for touch. Similarly, crossmodal attention effects (i.e., spatial attention to the uncued modality) showed a comparable time-course across modalities but were generally more pronounced for touch. By contrast, modulatory effects of intermodal attention (i.e., selection of the cued modality) emerged relatively late, with enhanced negativities observed for the cued than uncued modality beyond 200 ms. Notably, this effect was restricted to cued locations and was more pronounced for touch than for pain. Taken together, these results suggest the presence of largely overlapping mechanisms for attentional selectivity across touch and pain, operating first on space and only subsequently on modality.