Page 23 - Like me, or else... - Michelle Achterberg
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                                General introduction
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 After validating the experimental paradigm in children and adults, the next step was to examine to what extend individual variation in social evaluation were explained by genetics and environmental influences. That is, why are some children more sensitive to social evaluation than others, and how do nature and nurture contribute to this? To examine this, in chapter 4 I conducted behavioral genetic analyses on neural activation during social evaluation using a large developmental sample. Ultimately, in chapter 5, I examined individual differences in longitudinal changes of aggression regulation within childhood. Within-person changes provide a better indication of brain-behavior associations over time and can provide an actual reflection of development. In order to test within-person changes, I examined how neural mechanisms changed within individuals from middle (seven-to-nine-year-old) to late (nine-to-eleven-year-old) childhood, and to what extent these neural changes were related to changes in behavioral aggression.
Taken together, the first four chapters are devoted to an in-depth examination of social emotion regulation using the innovative SNAT paradigm. This paradigm allows to test neural mechanisms of social acceptance and rejection, as well as behavioral aggression in response to social feedback. Previous studies have suggested that social emotion regulation relies on a network of integrated connections between subcortical and cortical prefrontal brain regions (Olson et al., 2009; Chester et al., 2014; de Water et al., 2014; Peper et al., 2015; Silvers et al., 2016b; van Duijvenvoorde et al., 2016a). To date it remains an open question whether these networks are already in place during childhood, as previous studies often used older samples or only included a small sample of children. As L-CID compromises a large and statistically strong sample, I was able to investigate functional brain connectivity specifically in childhood. In chapter 6, I investigated the heritability of subcortical-PFC functional connectivity in childhood. The aim of this study was to test whether the subcortical-cortical connections that are central in neurodevelopmental models are already in place in childhood. Here I again made use of the large sample by including an in-sample replication approach to examine the robustness of the findings. Additionally, in chapter 7, I provide a comprehensive overview of pitfalls and possibilities in neuroimaging young children, which provides important methodological insights. Specifically, I examined what environmental as well as genetic factors contribute to scan quantity and quality. Here I explicitly compared different MRI modalities, including task-based fMRI, anatomical MRI, and structural and functional brain connectivity measures.
The ultimate goal of developmental neuroscience is to examine brain development from childhood, throughout adolescence, into adulthood and relate neural development to behavioral outcomes. A first step in that direction for social emotion regulation has been taken by relating structural brain connectivity to the ability to delay gratification (Olson et al., 2009; de Water et al., 2014; Peper et al., 2015). In chapter 8 I investigated the development of structural
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