The temporal order judgement of tactile and nociceptive stimuli is impaired by crossing the hands over the body midline

Crossing the hands over the midline impairs the ability to correctly judge the order of a pair of tactile stimuli, delivered in rapid succession, one to each hand. This impairment, termed crossed-hands deficit, has been attributed to a mismatch between the somatotopic and body-centred frames of reference, onto which somatosensory stimuli are automatically mapped. Whether or not such crossed-hands deficit occurs also when delivering nociceptive stimuli has not been previously investigated. In this study, participants performed a temporal order judgement (TOJ) task in which pairs of either nociceptive or tactile stimuli were delivered, one to each hand, while their arms were either crossed over the body midline or uncrossed. We observed that crossing the hands over the midline significantly decreases the ability to determine the stimulus order when a pair of nociceptive stimuli is delivered to the hands, and that this crossed-hands deficit has a temporal profile similar to that observed for tactile stimuli. These findings suggest that similar mechanisms for integrating somatotopic and body-centred frames of reference underlie the ability to localise both nociceptive and tactile stimuli in space.