Experimentally induced pain does not influence updating of peripersonal space and body representations following tool-use

Abstract

Representations of the body and peripersonal space can be distorted for people with some chronic pain conditions. Experimental pain induction can give rise to similar, but transient distortions in healthy individuals. However, spatial and bodily representations are dynamic, and constantly update as we interact with objects in our environment. It is unclear whether induced pain disrupts the mechanisms involved in updating these representations. In the present study, we sought to investigate the effect of induced pain on the updating of peripersonal space and body representations during and following tool-use. We compared performance under three conditions (pain, active placebo, neutral) on a visuotactile crossmodal congruency task and a tactile distance judgement task to measure updating of peripersonal space and body representations, respectively. Consistent with previous findings, the difference in crossmodal interference from visual distractors in the same compared to opposite visual field to the tactile target was less when tools were crossed than uncrossed. This suggests an extension of peripersonal space to incorporate the tips of the tools. Also consistent with previous findings, estimates of the felt tactile distance judgements decreased after active tool-use. In contrast to our predictions, however, we found no evidence that pain interfered with performance on either task when compared to the control conditions. Our findings suggest that the updating of peripersonal space and body representations is not disrupted by induced pain. That is, experiencing acute pain does not give rise to distorted representations of the body and peripersonal space that can be present in people with chronic pain conditions.

Altered updating of bodily and spatial representations after tool-use in complex regional pain syndrome

“…In a previous study [115] we were able to detect tool-use dependent changes in TDJs using this shorter version of the TDJ task. We used the same materials, and procedure for the TDJs as for our previous study [115]. Two flat-ended circular rods (1 mm diameter) were attached to a bow compass to enable the experimenter to accurately adjust the distance between the two points.…”

“…The protocol (see Fig. 1) was similar to that for our previous work examining the effect of experimentally induced pain on updating of bodily and spatial representations [115]. All participants provided informed written consent prior to undergoing a clinical assessment and completing selfreport questionnaires.…”

“…We also wished to keep the task as brief as possible because we were interested in comparing the judgements for the two arms, hence we needed to make this task quick enough to capture any potentially short-lived effects of tool-use [27]. In a previous study [115] we were able to detect tool-use dependent changes in TDJs using this shorter version of the TDJ task. We used the same materials, and procedure for the TDJs as for our previous study [115].…”

“…The passive Set was similar, but instead of the participants moving the tools, the experimenter moved the tools from the crossed to uncrossed Arrangement (or vice versa) half-way through the Set. The materials that we used for the CCT were from our previous study examining the effect of experimentally induced arm pain on updating of spatial and bodily representations in pain-free controls [115]. We used two aluminium tools that resembled golf clubs (75cm long, Fig.…”

“…any differences between responses for stimuli applied to the CRPS-affected/non-dominant versus nonaffected/dominant arm). This was also the response format we used in a previous study [115]. Pain and other CRPS symptoms prevented people with lower limb CRPS from using their affected limb to make foot pedal responses.…”