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Chapter 6
Post-Hoc Examination of Subcortical-Subcortical
Connectivity
To investigate limbic/subcortical-subcortical brain connectivity in more detail, we used two additional ROIs of the HPC, TH. Moreover, we investigated connectivity between the VS and the AMY. Connectivity patterns replicated across sample I and II (Fig 3b, Table S6). The overall pattern showed pronounced positive connectivity between subcortical regions, see Fig 3b. Interestingly, the HPC ROI showed strong positive connectivity with AMY (Fig 3b, Table 4). More stringent thresholded (smaller) HPC ROIs resulted in similarly strong positive connectivity patterns (see supplementary materials, Fig S3), indicating that this strong connectivity was not inflated by cross-boundary blurring. VS-Hippocampus showed negative connectivity (Fig 3b, Table 4), however, note that VS-HPC connectivity was not significantly different from zero in Sample II (Table S6). VS- TH connectivity was significantly stronger than AMY-TH connectivity, which was negative, and not significantly different from zero in sample II (Table S6). The connectivity estimate between the VS and AMY was small and not significantly different from zero in both samples (Fig 3 and Table S6). There were no significant gender differences in limbic/subcortical-subcortical connectivity (sample I and II combined). We found weak negative correlations between age and VS-HPC connectivity in (r=-.20, p=.01), and VS-AMY connectivity (r=-.17, p=.04).
Heritability of Subcortical-Cortical Connectivity
An overview of ACE models for limbic/subcortical-cortical brain connectivity between seed (VS and AMY) and cortical ROIs (vmPFC, vACC, OFC, dmPFC, dACC, dlPFC) is provided in Table 5. Comparisons of the full ACE model with more parsimonious AE, CE and E models are displayed in Table S7 (VS) and Table S8 (Amygdala). Note that the estimates of the different components add up to 1 (100%). The overall pattern showed that the variance in VS-PFC connectivity was best accounted for by genetic and unique environmental factors (including measurement error). That is to say, the A estimate was moderately high for connectivity between VS and vmPFC (A=67%, E=33%), OFC (A=32%, C=9% E=59%), dmPFC (A=37%, C=1%, E=63%), dACC (A=46%, E=54%), and dlPFC (A=19%, E=81%), see Table 5. In addition to genetic influences, VS-vACC connectivity also showed influences of shared environment (A= 12%, C=17%, E=71%). Variance in AMY- dorsalPFC connectivity was less influenced by genetics, with small contributions of the A component for connectivity between AMY and dmPFC (A=8%, C=0%, E=92%), dACC (A=8%, C=0%, E=92%), and dlPFC (A=14%, C=0%, E=86%). AMY-vACC connectivity showed moderately high estimates of the shared environment (C=35%, E=65%), with no influence of genetics (A=0%). AMY-vmPFC connectivity
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