Figure 3.6 Critical regions and reciprocal relations of the social brain

      (Reproduced with permission from Adolphs, 2003). Reproduced with permission from Nature Publishing.

Myelinated axons are the centerpiece of neural networks that provide the interlinking of brain regions. In graph theory, a connector (pathway) is referred to as an “edge,” which connects different regions through nodes and hubs. The most efficient connections, if fully functional, probably involve the fewest and shortest pathways (edges). What is shown in Figure 3.2 is a whole‐brain schematic using DTI‐derived myelinated axons aggregated into a network. The lines in Figure 3.2c represent pathways, the size of the line and different shading reflecting different aspects of a functioning network and their strength, possibly related to importance. As more networks come online with maturation, the spherical representation of a hub or node importance, is reflected by its increased size (Figure 3.2c).

Kennedy and Adolphs (2012) use these and other methods to derive a cognitive neuroscience framework for these key brain regions and networks that participate in self‐regulation and monitoring of social behavior. Their model, presented in Figure 3.7, is based on just four networks – amygdala, mentalizing, empathy, and mirror (see Tables 3.1 and 3.2). As will be discussed in the next section, numerous networks are at play in regulating the social brain, but for demonstrable purposes the networks discussed by Kennedy and Adolphs are what are presented here.

Since most of the prior research and clinical understanding for the role of these brain regions in social behavior came from the damaged brain, it was important for investigators of age‐typical, healthy brain development to study these candidate “social brain” regions in those who did not have some acquired or developmental neuropathology. Social and neuropsychological methods through behavioral assessments had long been able to identify children with differences in social and adaptive behaviors, for example, the acquisition of reciprocal play. Like most behaviors, using behavioral testing and observational studies, the acquisition and mastery of certain social behaviors could be plotted on a spectrum – early versus late, age‐typical versus delayed, etc. The paradigm shift with neuroimaging was to design experiments with these types of differing behavioral characteristics of social behavior and then scan these children and adolescent research participants, quantitatively analyzing their brains with some of the neuroimaging techniques described in this chapter, especially in the next section. Similarly, these neuroimaging methods have been applied to the study of children with neuropsychiatric disorders, with particular emphasis on clinical syndromes involving social‐emotional functioning (Li et al., 2020). The next section discusses some of these methods and their application to studying the social brain.

Table 3.1 Candidate regions that participate in the social brain.