Summary
What circuits in the brain mediate our tendency to socially connect with others? An article by Bickart et al 2012 finds that the functioning of particular brain circuits—including specific parts of the amygdala, an important hub of the “emotional”/limbic system of the brain—is related to the size and complexity of people’s social networks.
More details
What circuits in the brain mediate our tendency to socially connect with others? Many studies have implicated brain circuits involving the amygdala and the frontal cortex in social behaviors. Some of these studies (e.g. Bickart et al 2011) have found a positive correlation between size of social networks and size of the amygdala, an important hub of the “emotional”/limbic system of the brain. Now a new study (Bickart et al 2012) provides more detailed information about the relationship between specific brain circuits involving subdivisions of the amygdala and size of social networks in healthy, young adult humans. Bickart and co-workers (2012) measured size of individuals’ social networks using the Social Network Index (Cohen et al 1997). They used fMRI to measure the size of the each person’s amygdala, and used a method called resting-state functional connectivity magnetic resonance imaging (fcMRI) to assess connectivity between amygdala sub-regions and various other brain regions. Replicating their previous work (Bickart et al 2011), this 2012 study found a positive correlation between size of the amygdala and size of the social network. In addition, they found that the strength of a circuit supporting social perception (ventrolateral amygdala connected to orbitofrontal cortex, fusiform gyrus, ventromedial temporal cortex, and superior temporal sulcus) and a circuit supporting social affiliation (medial amygdala connected to ventromedial prefrontal cortex, rostral anterior cingulate cortex, and nucleus accumbens, and ventromedial hypothalamus) predicted social network size. However, social network size was not related to the strength of a circuit including the dorsal amygdala that supports social aversion. Moreover, social network size and complexity was not related to connectivity within other networks important for social cognition that do not include the amygdala, specifically networks involved in mentalizing (dorsomedial prefrontal cotex connected to temporoparietal junction) or in mirror networks (ventral premotor cortex, posterior superior temporal sulcus, and intraparietal sulcus). The authors note that “This dissociation underscores the value of studying the component processes that contribute to social connectedness since there are clearly important divisions of labor. In this case, the size and complexity of a person’s social network depends more on corticolimbic circuitry that is important for affective processing (Barett and Bar, 2009), which in part evaluates the salience of signals from other people (Seeley et al., 2007), than on corticocortical networks that have more limited relevance for affective processing” (Bickart et al 2012). Importantly, the authors note that their findings do not indicate the extent to which the strength of these circuits related to social network size are “hard-wired” by genetics, or are modifiable by experience or other environmental factors.
References
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