Table 1.

Results of the additive analysis for the whole average and regional FA values in HCP subjects, including the heritability values (first column) and significance values for each of the five covariates. Regions of interest (ROIs) examined along the ENIGMA-DTI skeleton as defined by the JHU white matter parcellation atlas (Mori et al., 2008).

Trait	h2±SE (p)	Covariates
		Age (p)	Age2(p)	Sex(p)	Age*Sex(p)	Age2*Sex (p)	Variance explained (%)
Average FA	0.88±0.03 (10−25)	0.60	0.75	6.6·10−8	0.48	0.56	10.9
Genu of the corpus callosum (GCC)	0.89±0.02 (10−30)	0.19	0.23	8.6·10−5	0.48	0.08	4.6
Body of the corpus callosum (BCC)	0.90±0.02 (10−25)	0.32	0.44	2.9·10−8	0.92	0.36	11.1
Splenium of corpus callosum (SCC)	0.90±0.02 (10−26)	0.40	0.57	1.8·10−9	0.92	0.47	12.9
Fornix (FX)	0.53±0.08 (10−9)	0.50	0.73	3.8·10−8	0.26	0.62	14.7
Cingulum (cingulate gyrus) - L and R combined (CGC)	0.81±0.04 (10−22)	0.45	0.46	8.0·10−8	0.30	0.18	9.2
Corona radiata - L and R anterior, superior and posterior sections combined (CR)	0.87±0.03 (10−23)	0.64	0.62	2.0·10−3	0.98	0.86	3.8
External capsule - L and R combined (EC)	0.82±0.05 (10−15)	0.35	0.87	7.9·10−5	0.44	0.78	6.5
Internal capsule - L and R anterior limb, posterior limb, and retrolenticular parts combined (IC)	0.86±0.03 (10−28)	0.53	0.67	3.3·10−13	0.94	0.58	19.1
Inferior fronto-occipital fasciculus - L and R combined (IFO)	0.78±0.06 (10−13)	0.15	0.41	0.3	0.89	0.77	1.6
Posterior thalamic radiation - L and R combined (PTR)	0.85±0.03 (10−23)	0.89	0.22	2.1·10−7	0.87	0.23	8.6
Superior fronto-occipital fasciculus - L and R combined (SFO)	0.76±0.05 (10−18)	0.89	0.41	0.2	0.89	0.65	1.3
Superior longitudinal fasciculus - L and R combined (SLF)	0.87±0.03 (10−28)	0.32	0.34	1.5·10−3	0.75	0.40	3.1
Sagittal stratum (include inferior longitudinal fasciculus and inferior fronto-occipital fasciculus) - L and R combined (SS)	0.81±0.05 (10−19)	0.33	0.24	6.2·10−10	0.73	0.18	12.8
Corticospinal tract - L and R combined (CST)	0.66±0.05 (10−18)	0.20	0.74	7.7·10−7	0.29	0.67	9.3