Table 3.
Heritability estimates for diffusion indices by individual fiber tracts (sub‐tracts indented) and average values of all tracts
| FA | MD | AD | RD | |||||
|---|---|---|---|---|---|---|---|---|
| Fiber Tract | a2 | (95% CI) | a2 | (95% CI) | a2 | (95% CI) | a2 | (95% CI) |
| Fornix‐R | 0.09 | (0.00; 0.50) | 0.11 | (0.00; 0.56) | 0.08 | (0.00; 0.56) | 0.13 | (0.00; 0.56) |
| Fornix‐L | 0.00 | (0.00; 0.42) | 0.56 | (0.33; 0.68) | 0.61 | (0.41; 0.72) | 0.52 | (0.27; 0.65) |
| Cingulate Portion of the Cingulum‐R | 0.69 | (0.31; 0.82) | 0.66 | (0.43; 0.76) | 0.71 | (0.47; 0.80) | 0.74 | (0.48; 0.81) |
| Cingulate Portion of the Cingulum‐L | 0.50 | (0.10; 0.76) | 0.61 | (0.34; 0.72) | 0.59 | (0.22; 0.70) | 0.65 | (0.25; 0.79) |
| Parahippocampal Portion of the Cingulum‐R | 0.28 | (0.00; 0.56) | 0.21 | (0.00; 0.57) | 0.40 | (0.11; 0.56) | 0.11 | (0.00; 0.55) |
| Parahippocampal Portion of the Cingulum‐L | 0.51 | (0.22; 0.65) | 0.68 | (0.49; 0.78) | 0.51 | (0.19; 0.64) | 0.71 | (0.50; 0.80) |
| Corticospinal/Pyramidal Tract‐R | 0.37 | (0.00; 0.73) | 0.00 | (0.00; 0.34) | 0.43 | (0.05; 0.59) | 0.00 | (0.00; 0.43) |
| Corticospinal/Pyramidal Tract‐L | 0.52 | (0.02; 0.65) | 0.23 | (0.00; 0.42) | 0.38 | (0.00; 0.54) | 0.09 | (0.00; 0.46) |
| Anterior Thalamic Radiation‐R | 0.46 | (0.00; 0.67) | 0.53 | (0.19; 0.65) | 0.62 | (0.35; 0.73) | 0.55 | (0.12; 0.67) |
| Anterior Thalamic Radiation‐L | 0.45 | (0.16; 0.60) | 0.53 | (0.27; 0.66) | 0.67 | (0.47; 0.76) | 0.48 | (0.22; 0.62) |
| Uncinate‐R | 0.64 | (0.22; 0.80) | 0.51 | (0.08; 0.75) | 0.57 | (0.18; 0.70) | 0.43 | (0.03; 0.76) |
| Uncinate‐L | 0.43 | (0.01; 0.72) | 0.47 | (0.11; 0.79) | 0.52 | (0.13; 0.65) | 0.47 | (0.14; 0.80) |
| Inferior Longitudinal Fasciculus‐R | 0.73 | (0.49; 0.80) | 0.80 | (0.63; 0.86) | 0.70 | (0.44; 0.79) | 0.79 | (0.63; 0.85) |
| Inferior Longitudinal Fasciculus‐L | 0.69 | (0.36; 0.78) | 0.76 | (0.52; 0.83) | 0.66 | (0.30; 0.81) | 0.73 | (0.51; 0.81) |
| Inferior Fronto‐Occipital Fasciculus‐R | 0.73 | (0.52; 0.81) | 0.71 | (0.54; 0.80) | 0.69 | (0.50; 0.78) | 0.71 | (0.52; 0.79) |
| Inferior Fronto‐Occipital Fasciculus‐L | 0.69 | (0.27; 0.77) | 0.68 | (0.41; 0.77) | 0.65 | (0.39; 0.75) | 0.68 | (0.38; 0.77) |
| Corpus Callosum | 0.79 | (0.45; 0.85) | 0.70 | (0.44; 0.78) | 0.67 | (0.41; 0.76) | 0.72 | (0.45; 0.80) |
| Forceps Major | 0.72 | (0.42; 0.79) | 0.75 | (0.55; 0.82) | 0.57 | (0.27; 0.68) | 0.77 | (0.57; 0.84) |
| Forceps Minor | 0.74 | (0.55; 0.81) | 0.63 | (0.20; 0.75) | 0.54 | (0.12; 0.67) | 0.71 | (0.34; 0.79) |
| Superior Longitudinal Fasciculus‐R | 0.77 | (0.48; 0.84) | 0.76 | (0.52; 0.83) | 0.75 | (0.58; 0.82) | 0.74 | (0.42; 0.81) |
| Superior Longitudinal Fasciculus‐L | 0.82 | (0.64; 0.87) | 0.78 | (0.58; 0.84) | 0.64 | (0.22; 0.79) | 0.79 | (0.54; 0.85) |
| Temporal Superior Longitudinal Fasciculus‐R | 0.82 | (0.55; 0.87) | 0.77 | (0.57; 0.84) | 0.70 | (0.52; 0.79) | 0.79 | (0.53; 0.85) |
| Temporal Superior Longitudinal Fasciculus‐L | 0.81 | (0.60; 0.87) | 0.77 | (0.53; 0.84) | 0.55 | (0.14; 0.78) | 0.79 | (0.53; 0.85) |
| Parietal Superior Longitudinal Fasciculus‐R | 0.73 | (0.43; 0.80) | 0.74 | (0.52; 0.81) | 0.74 | (0.56; 0.82) | 0.71 | (0.37; 0.79) |
| Parietal Superior Longitudinal Fasciculus‐L | 0.81 | (0.66; 0.87) | 0.77 | (0.54; 0.84) | 0.70 | (0.44; 0.79) | 0.79 | (0.59; 0.85) |
| Superior Corticostriate‐R | 0.63 | (0.30; 0.85) | 0.68 | (0.41; 0.77) | 0.70 | (0.50; 0.79) | 0.72 | (0.32; 0.81) |
| Superior Corticostriate‐L | 0.58 | (0.23; 0.82) | 0.76 | (0.63; 0.84) | 0.71 | (0.55; 0.80) | 0.77 | (0.59; 0.84) |
| Frontal Superior Corticostriate‐R | 0.53 | (0.21; 0.84) | 0.66 | (0.41; 0.76) | 0.70 | (0.50; 0.79) | 0.74 | (0.36; 0.81) |
| Frontal Superior Corticostriate‐L | 0.66 | (0.29; 0.83) | 0.78 | (0.63; 0.84) | 0.75 | (0.59; 0.83) | 0.77 | (0.55; 0.84) |
| Parietal Superior Corticostriate‐R | 0.64 | (0.29; 0.84) | 0.68 | (0.42; 0.77) | 0.69 | (0.48; 0.78) | 0.73 | (0.33; 0.81) |
| Parietal Superior Corticostriate‐L | 0.64 | (0.26; 0.81) | 0.69 | (0.53; 0.79) | 0.68 | (0.48; 0.77) | 0.72 | (0.51; 0.80) |
| Striatal Inferior Frontal Cortex‐R | 0.66 | (0.23; 0.75) | 0.68 | (0.25; 0.77) | 0.69 | (0.42; 0.78) | 0.53 | (0.09; 0.74) |
| Striatal Inferior Frontal Cortex‐L | 0.53 | (0.13; 0.77) | 0.71 | (0.46; 0.79) | 0.72 | (0.51; 0.80) | 0.68 | (0.39; 0.77) |
| Inferior Frontal Superior Frontal Cortex‐R | 0.70 | (0.31; 0.81) | 0.69 | (0.41; 0.78) | 0.73 | (0.49; 0.81) | 0.68 | (0.37; 0.77) |
| Inferior Frontal Superior Frontal Cortex‐L | 0.79 | (0.53; 0.85) | 0.81 | (0.65; 0.87) | 0.77 | (0.57; 0.84) | 0.80 | (0.62; 0.86) |
| All Fiber Tracts | 0.80 | (0.47; 0.86) | 0.73 | (0.54; 0.81) | 0.72 | (0.56; 0.81) | 0.74 | (0.51; 0.82) |
| All Fiber Tracts (excluding Corpus Callosum)‐R | 0.70 | (0.34; 0.84) | 0.76 | (0.44; 0.83) | 0.76 | (0.60; 0.83) | 0.69 | (0.33; 0.83) |
| All Fiber Tracts (excluding Corpus Callosum)‐L | 0.73 | (0.35; 0.83) | 0.76 | (0.56; 0.83) | 0.78 | (0.64; 0.85) | 0.75 | (0.48; 0.82) |
| All Fiber Tracts‐R (including Corpus Callosum)‐R | 0.74 | (0.38; 0.84) | 0.71 | (0.49; 0.79) | 0.72 | (0.55; 0.80) | 0.71 | (0.41; 0.79) |
| All Fiber Tracts‐L (including Corpus Callosum)‐L | 0.81 | (0.50; 0.86) | 0.72 | (0.52; 0.80) | 0.64 | (0.44; 0.75) | 0.75 | (0.53; 0.82) |
FA, Fractional Anisotropy; MD, Mean Diffusivity; AD, Axial Diffusivity; RD, Radial Diffusivity; a2, Heritability Estimate; 95% CI, 95% Confidence Interval; R, right; L, left; All results are based on ACE univariate models. See Supporting Information Tables 1–4 (FA, MD, AD, and RD, respectively) for common and unique environmental estimates, within pair twin correlations, fits of the univariate models and P‐values when excluding genetic and common environmental effects.