Do Tonic Itch and Pain Stimuli Draw Attention towards Their Location?

Abstract

Background: Although itch and pain are distinct experiences, both are unpleasant, may demand attention, and interfere with daily activities. Research investigating the role of attention in tonic itch and pain stimuli, particularly whether attention is drawn to the stimulus location, is scarce.

Methods: In the somatosensory attention task, fifty-three healthy participants were exposed to 35-second electrical itch or pain stimuli on either the left or right wrist. Participants responded as quickly as possible to visual targets appearing at the stimulated location (ipsilateral trials) or the arm without stimulation (contralateral trials). During control blocks, participants performed the visual task without stimulation. Attention allocation at the itch and pain location is inferred when responses are faster ipsilaterally than contralaterally.

Results: Results did not indicate that attention was directed towards or away from the itch and pain location. Notwithstanding, participants were slower during itch and pain than during control blocks.

Conclusions: In contrast with our hypotheses, no indications were found for spatial attention allocation towards the somatosensory stimuli. This may relate to dynamic shifts in attention over the time course of the tonic sensations. Our secondary finding that itch and pain interfere with task performance is in-line with attention theories of bodily perception.

Figure 1

Schematic representation of the setup of the somatosensory attention task. The side of itch stimulation was contralateral to the pain stimulation (randomized across participants). During a block, an itch (itch block) or pain (pain block) stimulus was applied, or no stimulation (control blocks), while, after short onset of the fixation light, one of the target lights illuminated. Participants responded to the target light location using response buttons right below both target lights, at either the ipsilateral or the contralateral location as opposed to the somatosensory stimulation.

Figure 2

Reaction times (in ms) for participants (n = 51) responding to the visual target lights during the 35 s somatosensory itch (a) or pain bocks (b) or in control blocks, in which no somatosensory stimulation was applied (c). Visual targets were displayed either at the side of the itch or pain stimulation (i.e., ipsilateral trials, solid black line) or at the opposite side (i.e., contralateral trials, dashed grey line). In the case of control blocks, the solid black line is indicative for trials ipsilaterally to the attachment of the itch electrodes and the dashed grey line is indicative for trials ipsilaterally to the attachment of the pain electrodes.