**1. Introduction**

66 Infrared Spectroscopy – Life and Biomedical Sciences

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Neural activation to upright and inverted faces in infants measured by near

We perform appropriate social actions in the various scenes of everyday life. For example, we speculate about other people's intentions and feelings in order to understand them, or inhibit negative emotions such as anger toward them. Furthermore, we engage in altruistic behaviors out of consideration and empathy for unrelated others. Even for a person who we do not like, we can also be sensitive to his or her feelings and take the most suitable action that seems altruistic at the time. When we behave in such a prosocial way, how do we recognize ourself and others, regulate our emotions, and make decisions?

In this chapter, we first give an outline of the social neuroscience studies on empathy and perspective-taking that use brain imaging techniques. Next, we review a near-infrared spectroscopy (NIRS) study reported by Nomura, Ogawa, and Nomura (2010), and finally we explain how we can use NIRS to investigate psychological and social neuroscience issues.

#### **1.1 Social cognition and social brain**

The mental ability underlying prosocial behaviors involving interaction with others is called *social cognition*, and the neural network involved in the functions of social cognition is called *social brain* (Brothers, 1990). Although brain imaging and lesion studies have always been related to psychology, over the past two decades the social brain studies have demonstrated the neural mechanisms underlying social cognition, including self-other recognition, emotion, recognition of facial expression, detection of intentionality and eye-direction, imitation of action, and theory of mind; these studies have been conducted in such fields as cognitive neuroscience, comparative cognitive science, social psychology, and developmental psychology (e.g., Decety & Cacioppo, 2011). Social cognitive neuroscience is a relatively new field studying social cognition from the standpoint of cognitive neuroscience (Cacioppo & Bernston, 1992; Ochsner & Lieberman, 2001).

In this chapter, we focus on empathy to others as a theme of social cognition. After we review recent studies on empathy by the approach of social cognitive neuroscience (mainly using functional magnetic resonance imaging (fMRI)), we introduce a NIRS study in which we investigated perspective taking associated with social relationships in the empathic process. First, however, we briefly explain the principle of NIRS measurement.

Using NIRS to Investigate Social Relationship in Empathic Process 69

Decety (2006) proposed a neuroscientific model corresponding to the conceptual model of empathy. This model consists of four major functional components: shared representation between the self and the other, mental flexibility to take the other's perspective, selfawareness, and emotion regulation. It is assumed that these four components dynamically

The four components are related to brain functions according to Decety's model. Shared representation is related to fronto-parietal networks based on the shared circuits between perception-action, and self-awareness is related to the inferior parietal lobule and the anterior insula on the right side. Mental flexibility is related to the prefrontal cortex. Emotion regulation is involved in the interaction between prefrontal and anterior cingulated

According to the model of empathy (Decety, 2006) described above, it is hypothesized that the interaction between bottom-up processing and top-down processing produces empathy. Bottom-up processing begins by an input of perceived data (information from the outside world) and interprets the perceived data under the influence of the physical characteristics of the stimuli. When we meet an other person, we are resonant to the movements and emotions of that person by the perceptual input automatically and unconsciously. In other words, emotions are contagious, and this processing proceeds in a bottom-up fashion automatically. On the other hand, top-down processing is influenced by the context of the present situation and by knowledge from past experience that individuals use as stimuli. Consequently, in order to understand others from the viewpoint of the others, intentional and conscious mental efforts are required. These cognitive empathic processes modulate emotion regulation and perspective taking, depending on the executive functions for higher

controlled processing of working memory, attention control, and memory retrieval.

Such higher cognitive-controlled functions are involved in the prefrontal cortex, including the ventrolateral prefrontal cortex (VLPFC). The right VLPFC is well known as a critical region for general inhibition and for regulating affective responses. The VLPFC also modulates the activity of the amygdala, which plays a key role in emotional appraisal and is related to detections of fear expression and eye-direction (Adolphs, Tranel, Damasio, & Damasio, 1994, 1995; Wicker, Michel, Henaff, & Decety, 1998). Therefore, the VLPFC is a critical area for the processing of emotional regulation via cortical-subcortical pathways

Previous studies on perspective taking have been reported in the brain imaging studies that deal with empathy for the physical pain of others (Decety & Grezes, 2006; Singer, Seymour, O'Doherty, Kaube, Dolan, & Frith 2004; Singer, Seymour, O'Doherty, Stephan, Dolan, & Frith, 2006). These studies found the existence of a "*pain network*" including the anterior cingulate cortex (ACC) and insula, which are involved in understanding the pain of others

Singer et al. (2004) used fMRI to compare brain activities between two conditions: when participants felt pain in oneself, and when participants observed that their beloved partner,

interact to produce empathy.

(Batson, Early, & Salvarini, 1997).

like one's own pain.

**1.3.3 "Pain network" which feels the pain of others** 

systems and subcortical emotion-generation systems.

**1.3.2 Empathy and ventrolateral prefrontal cortex** 
