Page 89 - Like me, or else... - Michelle Achterberg

Heritability of aggression following social evaluation
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addition, we will investigate possible brain-behavior relations between activation of these regions and the aggression measure. Based on prior studies (Riva et al., 2015; Achterberg et al., 2016b), we predicted that the lateral prefrontal cortex would be most strongly correlated to aggression regulation. Since the literature on the heritability of task-based fMRI is limited, and the current study is the first to study such heritability in middle childhood, no a priori hypotheses were formed for the exploratory analyses on heritability of neural activation.
Methods
Participants
Participants in this study took part in the longitudinal twin study of the Leiden Consortium on Individual Development (L-CID). The Dutch Central Committee Human Research (CCMO) approved the study and its procedures. Families with a twin born between 2006 – 2009, living within two hours travel time from Leiden, were recruited through municipal registries and received an invitation to participate by post. Parents could show their interest in participation using a reply card. 512 children (256 families) between the ages 7 and 9 were included in the L-CID study. Written informed consent was obtained from both parents. All twin-pairs had a shared home environment, were fluent in Dutch, and had normal or corrected-to-normal vision. The majority of the sample was Caucasian (91%) and right-handed (87%). Since the sample represents a population sample, we did not exclude children with a psychiatric disorder. Ten participants (2%) were diagnosed with an Axis-I disorder: eight with attention deficit hyperactivity disorder (ADHD); one with generalized anxiety disorder (GAD), and one with pervasive developmental disorder- not otherwise specific (PDD-NOS). Three participants did not have data from the SNAT due to technical problems. Therefore, our final behavioral sample consisted of 509 participants with a mean age of 7.95 ± 0.67 (age range: 7.02-9.68, 49% boys, see Table 1), with 253 complete twin pairs (55% MZ; based on DNA, see section 2.5). Data from 30 twin pairs were previously reported (Achterberg et al., 2017).
Twenty-seven participants did not perform the SNAT in the MRI scanner: 13 due to anxiety, 6 due to MRI contra-indications, 4 participants did not have parental consent for MRI participation, and 4 participants could not be scanned due to technical system failure. For all participants who underwent the MRI scan, anatomical MRI scans were reviewed and cleared by a radiologist from the radiology department of the Leiden University Medical Center (LUMC). Four anomalous findings were reported. To prevent registration errors due to anomalous brain anatomy, these participants were excluded. An additional 89 participants were excluded due to excessive head motion, which was defined as >3 mm motion (1 voxel) in any direction (x, y, z) in more than 2 blocks of the SNAT task (3 blocks in total). Finally, four participants were excluded due to
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