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Subcortical-PFC resting state connectivity
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scan, by using FMRIB's Linear Image Registration Tool (FLIRT, Jenkinson et al. (2002)). Next, an integrated version of boundary based registration (BBR; Greve and Fischl (2009)) was performed to improve the accuracy of the registration from high resolution EPI to subjects’ structural space. Lastly, FMRIB’s Nonlinear Imaging Registration Tool (FNIRT) with a 10 mm warp resolution was used to further refine registration from subjects’ structural space to standard MNI-152 space (Jenkinson and Smith, 2001; Jenkinson et al., 2002). To ensure accurate alignment, we visually inspected the summery of the registration for all participants. Examples of correct and incorrect registration can be found in the supplementary materials (Figure S1). In total, 11 participants were excluded due to registration problems (Table S1).
Table 2. Demographic characteristics of the mono- and dizygotic twins.
n
% boys
Left handed
AXIS-I disorder
Age (SD)
Range
Mean IQ (SD)
IQ range
Frames >0.5 mm FD
Monozygotic
74
(37 pairs) 35%
11% none
8.01 (0.72) 7.03-9.05 106.21 (12.09) 77.50-137.50 6%
Dizygotic
54
(27 pairs) 30%
6.00%
1 (ADHD)
7.88 (0.56) 7.15 - 8.94 103.52 (10.10) 77.50-130.00 7%
Statistics
χ(1, N=128)=0.43, p=.570
χ(1, N=128)=1.10, p=.354
χ(1, N=128)=1.38, p=.422
t(126)= 1.05, p=.294
t(126)=1.34, p=.184 t(126)=-0.97, p=.336
First-Level Seed Based Analysis
To investigate limbic/subcortical-cortical and limbic/subcortical-subcortical functional brain connectivity we used two subcortical seeds: the ventral striatum (VS) and the amygdala (AMY). The VS seed was based on the “limbic striatum” of the Oxford-GSK-Imanova structural connectivity striatal atlas (Tziortzi et al., 2014). The AMY seed was based on the Harvard-Oxford subcortical structural atlas. Seeds were anatomical, bilateral and thresholded at ≥75% probability, resulting in a VS seed of 197 voxels and an AMY seed of 254 voxels (Fig 1). To extract subject specific time series, seeds were first registered to subject space
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