**2. A NIRS study on perspective taking associated with social relationships by Nomura et al. (2010)**

#### **2.1 Purpose**

70 Infrared Spectroscopy – Life and Biomedical Sciences

who came to the laboratory with them, felt pain. In addition, the subjective empathic abilities of the participants were measured by questionnaires. The results show that the activated brain areas in common between the self condition (i.e., the participants themselves feel a pain) and the other condition (i.e., the participants observe their partners feeling a pain) were the bilateral anterior insula (AI), rostral anterior cingulate cortex (ACC), brainstem, and cerebellum. The activation levels of AI and ACC were significantly correlated positively with the empathic ability of individuals. These findings indicate that AI and ACC form the neural basis of understanding the emotions of one's own and others' pain and that the areas are

Furthermore, Singer et al. (2006) reported evidence that the empathic response to the pain of others is affected by the social relationship with the other. Namely, a person shows strong empathy for the pain of a favorite person, whereas a person does not show empathy for the pain of non-favorite persons. More interestingly, the results indicate that males appear to

In the experimental paradigm presented by Singer et al. (2006), participants played the Prisoner's Dilemma game in order to form a good or a bad impression of the opponent players (confederates) before measuring the brain activity by fMRI. In the game, one of two opponents made a cooperative and fair play toward the participants, whereas the other opponent made an uncooperative and unfair play. As a result, the participants came to like the fair opponent but came to dislike the unfair opponent. After the game, the brain activity was measured while the participants were observing the opponent receive a pain to the

The results showed that activation in the pain network encompassing the AI and ACC was observed for fair opponents in both male and female participants. However, this activation was significantly reduced in males for pain given to the unfair opponents. At the same time, it was reported that the activity of the nucleus accumbens, known as a reward-related area, increased depending on the degree that the participant strongly desired revenge. This means that for males, the pain felt by the opponents who show unfair behavior brings them

Nevertheless, even if they are disliked or unknown others, we can give them a helping hand when we encounter a situation in which the disliked or unknown other feels pain or distress, and we feel the need to help them from an ethical viewpoint. In order to clarify the neural mechanisms underlying such prosocial behaviors that suppress our own feelings, we must examine how the individual difference in perspective-taking ability influences not only the social relationships with the others but also influences the ability to evaluate the

Previous studies have demonstrated that emotion regulation processing is involved in the right VLPFC in relation to regulating or suppressing negative emotions caused by pain (Lieberman, Eisenberger, Crockett, Tom, Pfeifer, & Way, 2007; Wager, Davidson, Hughes, Lindquist, & Ochsner, 2008). In addition, it has also been reported that both self- and otherperspective taking are related to the activation of the pain network (Jackson, Brunet, Meltzoff, & Decety, 2006), and the activation of these areas increases depending on the degree of subjective empathic abilities as measured by questionnaires (Singer et al., 2004, 2006). Therefore, Nomura et al. (2010) focused on the mechanism of perspective taking in

related to emotion processing to evoke the empathic response to the pain of others.

feel pleasure in the pain of the non-favorite others.

emotional states based on the social relationship.

hand by electrical stimulation.

satisfaction in their revenge.

Following the paradigm of Singer et al. (2006), after playing the Prisoner's Dilemma game to form a good or a bad impression of the opponents, the participants observed the opponents' facial expressions (happy, neutral, and angry) and evaluated the valence of each facial expression on a 7-point scale ranging from "pleasantness" to "unpleasantness." The participants observed the facial expressions under two perspective-taking conditions: selfperspective vs. other-perspective. The brain activity was measured by using NIRS while the participants were evaluating the facial expressions. The participants were divided into two groups according to the points of the Interpersonal Reactivity Index (IRI) that they completed after all experiments. The IRI measures the components of empathy, from which we took particular note of perspective taking (e.g., 'I sometimes try to understand my friends better by imagining how things look from their perspective.').

The prediction was that a higher unpleasant emotion would be produced in the selfperspective condition rather than in the other-perspective condition during observation of an unfair opponent, since negative emotions should arise automatically when the participants observe the facial expression of the unfair opponent. On the other hand, in the other-perspective condition with the unfair opponent, the participants should rate the facial expression from the viewpoint of the unfair opponent while inhibiting the negative emotions for the disliked opponent, especially for a happy expression. Therefore, it was expected that the activation would increase in the right VLPFC in the other-perspective condition.

Moreover, the right VLPFC might play an important role for individuals who have a high ability of perspective taking. The right VLPFC would likely have a greater impact on taking the other-perspective, since top-down control from the prefrontal cortex functions very well for individuals with a high ability of perspective taking than for individuals with a low ability of perspective taking.
