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MRI scan quantity and quality in childhood
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(Power, 2017). By investigating both trait-like genetic influences as well as state- like environmental influences this study can provide insights in factors contributing to scan quantity and quality in developmental samples.
Methods
Participants
Participants in this study took part in the preregistered longitudinal twin study of the Leiden Consortium on Individual Development (L-CID; Euser et al. (2016)). The Dutch Central Committee on Human Research (CCMO) approved the study and its procedures (NL50277.058.14). Families with a same-sex twin born between 2006 – 2009, living within two hours travel time from Leiden, were recruited through municipal registries and received an invitation to participate via mail. 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 (mean age: 7.94±.67; 49% boys). Written informed consent was obtained from both parents. All children were fluent in Dutch or English and had normal or corrected-to-normal vision. The majority of the sample was Caucasian (90%) and right-handed (87%). Since the sample represents a population sample, we did not exclude children with a psychiatric disorder. For information on psychiatric disorders, we asked parents whether the children received a medical diagnosis from a psychologist or medical expert. Eleven participants (2%) were diagnosed with an Axis-I disorder: nine with attention deficit (hyperactivity) disorder (ADD/ADHD); one with generalized anxiety disorder (GAD), and one with pervasive developmental disorder-not otherwise specified (PDD-NOS). Participants’ intelligence (IQ) was estimated with the subtests ‘Similarities’ and ‘Block Design’ of the Wechsler Intelligence Scale for Children, third edition (WISC- III; Wechsler (1991)). Estimated IQs were in the normal range (72.50 - 137.50, mean: 103.58 ±11.76). Zygosity was determined by DNA analyses, which classified 55% of the twins as monozygotic.
Procedure
Participating twins visited the lab with their primary parent (defined as the parent that spends the most time with the children). Before the visit to the lab families received a step-by-step explanation of the MRI procedure, including a description of the magnetic field, the materials used during the MRI scan (earplugs, headphones, button box, alarm), and the movies that were available to watch. The step-by-step approach was specifically aimed at the young participants, and
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