Pain is important. The experience of pain can engage protective behavioral responses to harmful stimuli, and the effective communication of pain can warn others of potentially hazardous situations (and perhaps even the nature of that hazard). To be effectively communicated, however, observers must recognize the pain occurring in others, experience some proximal version of the pain themselves or at least understand its significance (sometimes sympathizing), and respond accordingly. These requirements reflect different aspects of the process termed empathy. The definition of empathy in psychological literature is sometimes obscure and often varied (depending on the stage in question), but generally reflects “an ability to detect accurately the emotional information being transmitted by another person” (Levenson&Ruef, 1992). Though a growing body of research on empathy exists, the neural processing of empathy in response to perceived pain, specifically in various social contexts, has not been fully explored.
Consider the following:
Scenario #1
You witness a person step on his own untied shoelaces causing him to fall on a sidewalk.
Scenario #2
You witness a person intentionally trip another person walking on the same sidewalk.
In both cases, you observe someone in a painful situation, but do you feel differently about the two scenarios? Might you perhaps laugh quietly to yourself in scenario #1? Would you be more sympathetic in scenario #2?
Using an event-related fMRI design, researchers at the Center for Cognitive and Social Neuroscience at the University of Chicago recently investigated how the perception of pain is modulated by agency (the cause of harm). They compared neural processing while individuals observed painful situations occurring by accident versus painful situations intentionally caused by another individual. Participants were exposed to four types of visual stimuli:
1. One person is in a painful situation caused by accident, e.g., an individual dropping a heavy bowl on her hand (PCS).
2. One person is involved in a non-painful situation, e.g., opening a door (NPS).
3. One person is in a painful situation caused by another individual, e.g., stepping purposely on someone's toe (PCO).
4. The two individuals are present and moving, but there is no pain (NPO).
(Akitsuki&Decety, 2009).
As shown above, the stimuli contain clearly distinguishable arms, hands and feet. However, participants can’t perceive facial or other bodily cues or auditory cues from which other emotional content might be derived. The authors define empathy generally as the “capacity to share and appreciate emotional and affective states in relation to oneself,” and the stimuli employed would seem to only allow for a form of empathetic perspective taking in which emotional consequences (and intentionality) are inferred from implicitly emotional but slightly ambiguous events.
Consistent with similar previous fMRI studies, Akitsuki and Decety found activation in the insula, somatosensory cortex (parietal lobe), anterior cingulate cortex (ACC), thalamus, periaqueductal gray (PAG) and cerebellum in response to the perception of pain. Images involving the presence of two people produced significant brain activation in the amygdala, the left inferior frontal gyrus (IFG), right parietal superior temporal sulcis (STS)/temporal parietal junction (TPJ), right temporal parietal, and medial prefrontal cortex (PFC); several regions associated with social cognition including the interpretation of intentionality of other people’s actions. Furthermore, significant activation in the left IFG was found specifically for scenes depicting painful situations inflicted by another individual.
It would also seem that agency modulates threat relevance in the amygdala-medial orbitofrontal cortex (OFC) network as activation in the left amygdala when processing the perception of intentional harm by another person was greater than processed perception of pain during the self-injury trials.
One interesting, though highly speculative, implication suggested by the authors is the ambiguous role the amygdala (involved in stimulus-reinforcement learning) and ventromedial PFC (involved in the formation of social attitudes) play in moral reasoning. Taken together, the neural findings in this study help to more clearly describe how social context (agency) modulates the interpretation of relevant threats, and possibly impacts the formulation of moral judgments concerning the intentionality of harm.
Akitsuki, Y.&Decety, J. (2009). Social context and perceived agency affects empathy for pain: An event-related fMRI investigation. Neuroimage; 47: 722-734.
Levenson, R.W. & Ruef, A.M. (1992). Empathy: A Physiological Substrate. Journal of Personality and Social Psychology; 63 (2): 234-246.
