Page 213 - Like me, or else... - Michelle Achterberg

MRI scan quantity and quality in childhood
211
minutes consisted of four task-based fMRI runs; the 45 minutes included all task- based fMRI runs and the 3DT1. The 60-minute protocol was the full L-CID scan protocol. 214 participants (49%) had sufficient quality on all scans in the first 30 minutes, with no significant gender differences (p=.149), see Figure 3c. 160 participants (33%) had sufficient quality on all scans in the first 45 minutes, with a larger proportion of girls being included than boys being included (χ2(1, N=433) =11.70, p=.001), see Figure 3c. 87 participants (20%) had sufficient quality on all eight scans of the full 60-min protocol, with a larger proportion of girls being included than boys being included (χ2(1, N=433) =8.85, p=.002), see Figure 3c. There were no age differences in scan quality over time.
Scan quality in relation to scanner related distress
Pearson’s correlations on the number of included scans (range=0-8, M=5.58, SD=2.47,) showed no association with excitement or tension (neither before the MRI simulation nor before the MRI scan, all p’s>.05). Children’s own estimate of excitement after the MRI scan was significantly correlated to scan quality (r=.13, p=.003), whereas tension after the MRI scan was not related to scan quality (r=.03, p=.52). Pearson’s correlations of the quantitative measures of scan quality (i.e. head motion based on the fMRI runs) showed a positive correlation between excitement before the MRI scan and mean FD (r=.12, p=.01), a positive association between absolute displacement and excitement before the MRI simulation (r=.10, p=.03) and before the MRI scan (r=.09, p=.04); and a negative association between absolute displacement and tension before the MRI simulation (r=-.09, p=.04). However, these correlations did not survive Bonferroni correction (Bonferroni corrected α=.008).
Genetic influences on scan quality
Within-twin correlations for general scan quality (percentage of scans included) were significantly stronger for MZ twins (rmz=.47, p<.001) than DZ twins (rdz=.19, p=.05), Z=2.40, p=.016. Behavioral genetic analyses revealed substantial influence of genetic factors (A=46%, 95% CI [33-58%]) and unique environment/measurement error (E=54%, 95% CI [42-67%]), with no influence of shared environment (C=0%, 95% CI [0-26%]).
Next, we investigated genetic influences on head motion, quantified by the mean framewise and mean absolute displacement over all fMRI runs. Within- twin correlations for framewise displacement were significantly stronger for MZ twins than DZ twins (rmz =.51, p<.001; rdz =.19, p=.05, Z=2.81, p=.002), see Table 3. Similar correlations were found for absolute displacement, with a significantly stronger association between MZ twins (rmz =.70, p<.001) than between DZ twins (rdz =.17, p=.09, Z=5.27, p<.001), indicating substantial genetic influences. More detailed behavioral genetic analyses showed that framewise displacement was significantly influenced by genetics, with a heritability estimate of 29% (95% CI:
7