Investigating the effects of pain observation on approach and withdrawal actions

Empathic pain observation does not influence automatic imitation in an online setting

Previous research has shown that empathic pain observation can lead to motor facilitation in the form of faster reaction times. However, it is unclear whether participants are focusing on the others' pain or simply focusing on their own discomfort/distress (from watching the videos) during the task. This is an important issue as self- vs other-oriented focusing plays a key role in empathic processing. To address this issue, we combined empathic pain observation with the automatic imitation task (AIT). Previous work has shown that AIT effects are smaller after experiencing pain, which has been interpreted as the result of the experience of pain leading to a self-oriented focus. If empathic pain observation similarly leads to a self-oriented focus, then we should expect similar AIT results after pain observation (smaller AIT effects); however, if it instead leads to an other-oriented focus, then we should see the opposite (larger AIT effects). Although we found initial evidence for the latter hypothesis (Experiment 1), subsequent failed replications suggests that we do not have sufficient evidence to claim that pain observation influences automatic imitation one way or the other (Experiment 2 and 3). We discuss some possible reasons for finding null results in these experiments and suggest future avenues of research to better elucidate this topic.

Prediction and action in cortical pain processing

Predicting that a stimulus is painful facilitates action to avoid harm. But how distinct are the neural processes underlying the prediction of upcoming painful events vis-à-vis those taking action to avoid them? Here, we investigated brain activity as a function of current and predicted painful or nonpainful thermal stimulation, as well as the ability of voluntary action to affect the duration of upcoming stimulation. Participants performed a task which involved the administration of a painful or nonpainful stimulus (S1), which predicted an immediately subsequent very painful or nonpainful stimulus (S2). Pressing a response button within a specified time window during S1 either reduced or did not reduce the duration of the upcoming stimulation. Predicted pain increased activation in several regions, including anterior cingulate cortex (ACC), midcingulate cortex (MCC), and insula; however, activation in ACC and MCC depended on whether a meaningful action was performed, with MCC activation showing a direct relationship with motor output. Insula's responses for predicted pain were also modulated by potential action consequences, albeit without a direct relationship with motor output. These findings suggest that cortical pain processing is not specifically tied to the sensory stimulus, but instead, depends on the consequences of that stimulus for sensorimotor control of behavior.

Exploring the relationship between social power and the ERP components of empathy for pain

Social power (the ability to control or influence another's thoughts, feelings, or behaviors) and empathy (the ability to both share and understand the thoughts and feelings of others) are fundamental to social life. Here, we explore the relationship between social power and the ERP components associated with empathy for pain. Participants were induced into states of high and low social power via a double blind version of the episodic recall task (e.g., "recall a time you felt powerful"). Afterward, they completed a pain categorization task, viewing pictures of hands that were in pain or not in pain, from a first-person or third-person visual perspective. Whereas both high and low social power states were associated with enhanced N2 amplitudes when observing another in pain, only the high social power state was associated with an enhancement of the P3. Based on this pattern of data, we tentatively suggest that, whereas social power does not seem to impact the initial emotional response to observing another's pain (as indexed by the N2), low social power might induce changes in the cognitive evaluation of another's pain relative to high social power (as indexed by the P3). We discuss our findings in relation to the broader literature on power and empathy.

To move or not to move: motor cortical output is enhanced during pain observation regardless of motor preparation state

Previous transcranial magnetic stimulation (TMS) studies have reported a decrease in motor cortical output during pain observation. In contrast, recent behavioral studies have shown that response times are faster after pain observation. This suggests that there is a mismatch between motor activity "during" versus "after" pain observation. We propose that these opposing effects of pain observation on motor activity may be explained by task constraints, as participants in TMS studies are instructed to keep still and relax their hands, whereas participants in behavioral studies maintain a state of readiness to respond. Task and methodological differences make it difficult to compare the results from TMS and behavioral paradigms examining the motor consequences of pain observation. As such, the aim of the current study is to directly test whether task instructions affect motor activity in TMS and behavioral measures of motor activity in the context of pain observation, within a single experiment. Participants watched videos of hands in painful versus nonpainful scenarios while TMS-induced motor evoked potentials were recorded. In the "active" block, participants responded to a cue that appeared immediately after each video; in the "passive" block, they relaxed their hand. Contrary to expectations, participants showed enhanced motor cortical output during pain observation (vs. no-pain) in "both" blocks. We discuss these results in relation to the wider literature on the social neuroscience of empathy.NEW & NOTEWORTHY The current study provides novel results showing an increase motor cortical output, measured via transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs), during empathic pain observation regardless of motor preparation state. Interestingly, this finding runs counter to the empathy for pain literature, which often finds a decrease in motor cortical output during empathic pain observation. We discuss potential explanations for this discrepancy and relate these results to the wider empathy for pain literature.