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. 2016 Feb 24;41(9):2224–2231. doi: 10.1038/npp.2016.14

Figure 2.

Figure 2

Skeletal white matter fractional anisotropy (FA) regions that mediate the effect of glutamic acid decarboxylase 1 (GAD1) rs3749034 on digit-span forward performance. Significant P-values indicated broad areas of the white matter skeleton FA that mediated the effect of GAD1 risk T-allele risk genotype on poor digit-span performance. We created a Z-statistic from voxel-wise Sobel tests for mediation based on the β-coefficients and standard error from (i) GAD1 regressed on tract-based spatial statistics (TBSS) skeleton FA (Figure 1), and (ii) TBSS skeleton FA regressed on digit-span performance (Supplementary Figure S2). The z-values then underwent threshold free clustering enhancement, and P-values are derived using permutation testing (N=10 000). Areas in red correspond to P<0.05 after correction for family-wise error. Green represents the mean FA skeleton overlaid on the FMRIB58_FA standard space image.