Mirroring Pain in the Brain: Emotional Expression versus Motor Imitation

Perception of pain in others via facial expressions has been shown to involve brain areas responsive to self-pain, biological motion, as well as both performed and observed motor actions. Here, we investigated the involvement of these different regions during emotional and motor mirroring of pain expressions using a two-task paradigm, and including both observation and execution of the expressions. BOLD responses were measured as subjects watched video clips showing different intensities of pain expression and, after a variable delay, either expressed the amount of pain they perceived in the clips (pain task), or imitated the facial movements (movement task). In the pain task condition, pain coding involved overlapping activation across observation and execution in the anterior cingulate cortex, supplementary motor area, inferior frontal gyrus/anterior insula, and the inferior parietal lobule, and a pain-related increase (pain vs. neutral) in the anterior cingulate cortex/supplementary motor area, the right inferior frontal gyrus, and the postcentral gyrus. The 'mirroring' response was stronger in the inferior frontal gyrus and middle temporal gyrus/superior temporal sulcus during the pain task, and stronger in the inferior parietal lobule in the movement task. These results strongly suggest that while motor mirroring may contribute to the perception of pain expressions in others, interpreting these expressions in terms of pain content draws more heavily on networks involved in the perception of affective meaning

Food-induced Emotional Resonance Improves Emotion Recognition

The effect of food substances on emotional states has been widely investigated, showing, for example, that eating chocolate is able to reduce negative mood. Here, for the first time, we have shown that the consumption of specific food substances is not only able to induce particular emotional states, but more importantly, to facilitate recognition of corresponding emotional facial expressions in others. Participants were asked to perform an emotion recognition task before and after eating either a piece of chocolate or a small amount of fish sauce – which we expected to induce happiness or disgust, respectively. Our results showed that being in a specific emotional state improves recognition of the corresponding emotional facial expression. Indeed, eating chocolate improved recognition of happy faces, while disgusted expressions were more readily recognized after eating fish sauce. In line with the embodied account of emotion understanding, we suggest that people are better at inferring the emotional state of others when their own emotional state resonates with the observed one

Modulation of Brain Activity during Action Observation: Influence of Perspective, Transitivity and Meaningfulness

The coupling process between observed and performed actions is thought to be performed by a fronto-parietal perception-action system including regions of the inferior frontal gyrus and the inferior parietal lobule. When investigating the influence of the movements' characteristics on this process, most research on action observation has focused on only one particular variable even though the type of movements we observe can vary on several levels. By manipulating the visual perspective, transitivity and meaningfulness of observed movements in a functional magnetic resonance imaging study we aimed at investigating how the type of movements and the visual perspective can modulate brain activity during action observation in healthy individuals. Importantly, we used an active observation task where participants had to subsequently execute or imagine the observed movements. Our results show that the fronto-parietal regions of the perception action system were mostly recruited during the observation of meaningless actions while visual perspective had little influence on the activity within the perception-action system. Simultaneous investigation of several sources of modulation during active action observation is probably an approach that could lead to a greater ecological comprehension of this important sensorimotor process

Brain responses to facial expressions of pain : emotional or motor mirroring?

The communication of pain requires the perception of pain-related signals and the extraction of their meaning and magnitude to infer the state of the expresser. Here, BOLD responses were measured in healthy volunteers while they evaluated the amount of pain expressed (pain task) or discriminated movements (movement task) in one-second video clips displaying facial expressions of various levels of pain. Regression analysis using subjects' ratings of pain confirmed the parametric response of several regions previously involved in the coding of self-pain, including the anterior cingulate cortex (ACC) and anterior insula (aINS), as well as areas implicated in action observation, and motor mirroring, such as the inferior frontal gyrus (IFG) and inferior parietal lobule (IPL). Furthermore, the pain task produced stronger activation in the ventral IFG, as well as in areas of the medial prefrontal cortex (mPFC) associated with social cognition and emotional mirroring, whereas stronger activation during the movement task predominated in the IPL. These results suggest that perception of the pain of another via facial expression recruits limbic regions involved in the coding of self-pain, prefrontal areas underlying social and emotional cognition (i.e. ‘mentalizing’), and premotor and parietal areas involved in motor mirrorin

The role of gender in the interaction between self-pain and the perception of pain in others

While self-pain motivates protective behaviors and self-oriented feelings, the perception of others' pain often motivates concern and prosocial behaviors toward the person suffering. The conflicting consequences of these 2 states raise the question of how pain is perceived in others when one is actually in pain. Two conflicting hypotheses could predict the interaction between these 2 signals: the threat value of pain hypothesis and the shared-representation model of pain empathy. Here, we asked 33 healthy volunteers exposed to acute experimental pain to judge the intensity of the pain felt by models expressing different levels of pain in video clips. Results showed that compared to a control warm stimulus, a stimulus causing self-pain increased the perception of others' pain for clips depicting male pain expressions but decreased the perceived intensity of female high pain expressions in both male and female participants. These results show that one's own pain state influences the perception of pain in others and that the gender of the person observed influences this interaction. Perspective : By documenting the effects of self-pain on pain perception in others, this study provides a better understanding of the shared mechanisms between self-pain and others' pain processing. It could ultimately provide clues as to how the health status of health care professionals could affect their ability to assess their patients' pain

Contrast models used in the analysis of imaging data in this study.

<p>Contrasts 1–4 replicate the analyses conducted in our previous study using a similar methodology [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107526#pone.0107526.ref001" target="_blank">1</a>]. Contrasts 5–9 test for overlap in brain activation across the observation and execution phases (conjunction) for all expressions in the pain task (5), for pain-related effects (pain vs. neutral) in the pain (6) and movement task (7), and for task effects (8: PT>MT; 9: MT>PT). Note: pain 0 = neutral; pain 1 = mild pain; pain 2 = moderate pain; pain 3 = strong pain; PT—pain task; MT = movement task; Obs = observation (clip); Exec = execution (response).</p><p>Contrast models used in the analysis of imaging data in this study.</p

Main effects of task during both observation and execution (pain expressions only^†):

<p>Peak values for areas of significant BOLD response change during both the viewing and performance of pain expressions, in the pain expression task condition (A) (PT—MT (Obs∩Exec)), versus the movement imitation task condition (B) (MT—PT (Obs∩Exec)). See note in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107526#pone.0107526.t002" target="_blank">Table 2</a> regarding identification and labeling of brain regions.</p><p>*p < 0.002.</p><p>† Results are reported for pain expressions only. Similar results were obtained when including the neutral condition with only one exception, in the right IFG</p><p>‡: t = 2.31; not significant.</p><p>Main effects of task during both observation and execution (pain expressions only<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107526#t004fn003" target="_blank">^†</a>):</p

Areas commonly activated during observation and execution phases of the pain task (Obs∩Exec(PT)).

<p>Significant clusters are shown in the mACC, the SMA, IFG/aINS, and IPL (p < 0.001, uncorrected). Inset figure shows rostral-caudal extent of activation in the right IFG. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107526#pone.0107526.t002" target="_blank">Table 2</a> for coordinates and peak t-values.</p

Effects of task during both observation and execution of pain expressions.

<p>For the pain task (PT—MT (Obs∩Exec); orange), a cluster of activation was observed in the left IFG, while bilateral clusters were observed in the IPL for the movement task (MT—PT (Obs∩Exec); blue) (p ≤ 0.005, uncorrected). Analysis included pain expressions only, no neutrals. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107526#pone.0107526.t004" target="_blank">Table 4</a> for coordinates and t-values of peaks.</p