Visual stimuli within peripersonal space prioritize pain

Abstract

Localizing pain not only requires a simple somatotopic representation of the body, but also knowledge about the limb position (i.e., proprioception), and a visual localization of the pain source in external space. Therefore, nociceptive events are remapped into a multimodal representation of the body and the space nearby (i.e., a peripersonal schema of the body). We investigated the influence of visual cues presented either in peripersonal, or in extrapersonal space on the localization of nociceptive stimuli in a temporal order judgement (TOJ) task. 24 psychology students made TOJs concerning which of two nociceptive stimuli (one applied to each hand) had been presented first (or last). A spatially non-predictive visual cue (i.e., lighting of a LED) preceded (80 ms) the nociceptive stimuli. This cue was presented randomly either on the hand of the participant (in peripersonal space), or 70 cm in front of the hand (in extrapersonal space), and either on the left or on the right side of space. Biases in spatial attention are reflected by the point of subjective simultaneity (PSS). The results revealed that TOJs were more biased towards the visual cue in peripersonal space in comparison with the visual cue in extrapersonal space. This study provides evidence for the crossmodal integration of visual and nociceptive stimuli in a peripersonal schema of the body. Future research with this paradigm will explore crossmodal attention deficits in chronic pain populations.