Figure 6. Asymmetry heritability.

Heritability of areal (A) and thickness asymmetry (B) estimated cortex-wide using SNP-based (UKB data; top rows) and twin-based methods (HCP data; bottom rows). Unthresholded effect maps are shown. Parcels in black outline show significance at p[FDR]<.05. Cyan parcels depict the point of maximum observed SNP-heritability (area h²=16.4%; thickness h²=16.6%). (C) Significant SNP-based genetic correlations (FDR-corrected) between areal (lower matrix) and thickness asymmetries (upper matrix). For area, SNP-based genetic correlations explained several phenotypic correlations (Figure 5A). For thickness, one pair survived FDR-correction (shown). See Figure 6—figure supplement 1 for comparison with genetic correlation estimates from the twin-based HCP sample. Individual AI’s in rightward clusters are inversed, such that positive genetic correlations reflect asymmetry-asymmetry genetic relationships, regardless of direction of mean asymmetry in the cluster (i.e. higher asymmetry in the population-direction). Yellow and blue brain clusters/colours denote leftward and rightward asymmetries, respectively (clusters numbered for reference).

Figure 6—figure supplement 1. Genetic correlations exhibiting pre-corrected significance (p<0.05).

(A) SNP- and twin-based genetic correlations exhibiting pre-corrected significance (p<0.05) for areal asymmetry clusters and (B) thickness asymmetry clusters. Note that all clusters exhibiting significant SNP-based heritability (pre-corrected) were tested in both designs (78 tests for area; 55 for thickness; see Supplementary file 1H–I; NT = Not Tested). As such, some traits tested in the twin-based analysis were not found to exhibit significant twin-based heritability; hence, these results should be interpreted cautiously. Of note, a genetic correlation estimated at the boundary of parameter space (–1, 1) implies the genetic component of the phenotypes cannot be empirically distinguished. This is expected for phenotypes with a shared genetic basis, but may also reflect sampling variability of the estimator. Subscript denotes 95% CI (not estimated by GCTA; NA indicates that the optimizer could not find the confidence interval limit). ** denotes FDR-corrected significance. Individual AI’s in rightward clusters are inversed such that positive genetic correlations reflect asymmetry-asymmetry genetic relationships, regardless of direction of mean asymmetry in the cluster (i.e. higher asymmetry in the population-direction). Yellow and blue brain clusters/colours denote leftward and rightward asymmetries, respectively (clusters numbered for reference).