Increasing self-other bodily overlap increases sensorimotor resonance to others' pain

Abstract

Empathy for another person's pain and feeling pain oneself seem to be accompanied by similar or shared neural responses. Such shared responses could be achieved by mapping the bodily states of others onto our own bodily representations. We investigated whether sensorimotor neural responses to the pain of others are increased when experimentally reducing perceived bodily distinction between the self and the other. Healthy adult participants watched video clips of the hands of ethnic ingroup or outgroup members being painfully penetrated by a needle syringe or touched by a cotton swab. Manipulating the video presentation to create a visuospatial overlap between the observer's and the target's hand increased the perceived bodily self-attribution of the target's hand. For both ingroup and outgroup targets, this resulted in increased neural responses to the painful injections (compared with nonpainful contacts), as indexed by desynchronizations of central mu and beta scalp rhythms recorded using electroencephalography. Furthermore, these empathy-related neural activations were stronger in participants who reported stronger bodily self-attribution of the other person's hand. Our findings provide further evidence that empathy for pain engages sensorimotor resonance mechanisms. They also indicate that reducing bodily self-other distinction may increase such resonance for ingroup as well as outgroup targets.

Keywords: Body ownership; Empathy; Pain; Racial bias; Self; Self-other distinction.

Fig 1.

Schematic depiction of the experimental settings used in the behavioral experiment. (a) No-overlap projection, (b) overlap projection

Fig 2.

Schematic display of the visual stimuli and their timing. The trial sequence began with presenting a fixation cross (duration varied between 1,500 and 2,000 ms), followed by a static display of a hand (duration = 1,500 ms). This was followed by the video showing the action of hand treatment (i.e., motion of a needle syringe or a cotton swab, duration = 1,500 ms). After the needle syringe or the cotton swab had reached their final position, a static display of the last frame of the video was shown (duration = 1,500 ms). Next trial followed automatically without delay

Fig 3.

Ratings of perceived bodily self-attribution of the target hand (mean ± standard error of the mean) in the no-overlap setup (n = 20) and the overlap setup (n = 22) plotted separately for ingroup (light bars) and outgroup target hands (dark bars)

Fig 4.

Dynamics of sensorimotor oscillations during observation of the videos. Inserted is a schematic drawing of head depicting positions of EEG sensors (small black dots) and sensors selected for signal analysis (blue circles: left ROI, red circles: right ROI). Mean ERSD (n = 29) in the Ingroup Pain condition is plotted for one sensor overlying left sensorimotor cortex (position C3 of the international 10-20 system, see dashed rectangle in the inserted head plot). The pattern of spectral changes over time at other sensors was similar. Rectangles depict windows for analysis of experimental effects (time window 1: treatment action, time window 2: treatment endpoint)

Fig 5.

Mean mu ERSD (a) and beta ERSD (b) in each experimental condition in time window 300-1,500 ms across the ROIs. Horizontal bars: group means, boxes: 95% within-subject confidence intervals of the mean corrected for between-subject error variability (Morey, 2008). Circles: values of individual participants. Note the different scales for mu and beta ERSD. Plots were created using the function pirateplot of the R-package yarrr (Phillips, 2017)