Page 106 - Like me, or else... - Michelle Achterberg

Chapter 4
Discussion
This study aimed to investigate genetic and shared environmental influences on neural activity and aggression following social feedback in children. Consistent with prior studies, negative social feedback resulted in behavioral aggression (Achterberg et al., 2016b; Achterberg et al., 2017). Behavioral genetic modeling revealed that aggression following negative feedback (negative-positive and negative-neutral) was influenced by genetic as well as shared and unique environmental influences. Genetic influences ranged from 10-20%, whereas approximately 7% of the variance was explained by shared environmental influences. Although previous studies have also found influences of shared environment, with similar (Ferguson, 2010) or higher estimates (Rhee and Waldman, 2002; Porsch et al., 2016), most studies have suggested stronger genetic influences (around 50%) on behavioral aggression (Rhee and Waldman, 2002; Ferguson, 2010). These differences can be partly attributed to the way the aggression was assessed. Indeed, a review of Tuvblad and Baker (2011) showed that twin correlations of aggression based on parent/ teacher reports were twice as high as twin correlations of observed aggressive behavior. Using single raters for multiple children might result in inflated genetic influences (Tuvblad and Baker, 2011), and an experimental design can overcome such rater bias. This study is the first to use an experimental task to test genetic influences on reactive social aggression in a developmental twin-sample. It shows that environmental factors are important predictors of reactive aggressive behaviors. In line with our results, longitudinal stability in reactive aggression has been shown to be influenced by environmental effects (Tuvblad et al., 2009).
Our analyses of neural responses to negative, positive, and neutral social feedback showed that brain activation in the ACCg and anterior insula was related to general valiance/ social saliency. The ACCg has been suggested to be sensitive to determining others’ motivation (Apps et al., 2016), which is important in the processing of social feedback, irrespective of whether it is positive or negative. Moreover, the ACCg has been shown to have strong structural and functional connectivity with the anterior insula (Apps et al., 2016), and together these regions have been indicated as the salience network (Damoiseaux et al., 2006; van Duijvenvoorde et al., 2016a). Our results show that activation of regions coding social saliency is present already in childhood, indicating this might be a core social motivational mechanism in humans. Previous social evaluation studies did not report heightened activation that was specific for negative social feedback (Gunther Moor et al., 2010b; Guyer et al., 2012; Achterberg et al., 2016b; Achterberg et al., 2017), which might be due to the smaller samples in previous studies (n=30-60) as compared to the current study (N=385). In the current study, medial PFC and IFG were activated during negative feedback. Interestingly, the ACCg is connected to the portions of the mPFC that signal other-oriented
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