Descriptive Statistics for the DTI measures.

<p><u>Notes</u>: FA – Fractional anisotropy; MD- Mean diffusivity; RD- Radial diffusivity; AD – Axial diffusivity; SD – standard deviation; CC – corpus callosum. The means are calculated considering all the voxels within that subregion^a.</p><p>Descriptive Statistics for the DTI measures.</p

Mid- sagittal slice showing the divisions of corpus callosum into 5 regions anterior to posterior (A–E) using the parcellation method of Chao et al. [39].

<p>Mid- sagittal slice showing the divisions of corpus callosum into 5 regions anterior to posterior (A–E) using the parcellation method of Chao et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0113181#pone.0113181-Chao1" target="_blank">[39]</a>.</p

Demographics and Characteristics of the Twin Sample.

<p><u>Notes:</u> MZ – monozygotic twins; DZ- Dizygotic twins; M –mean; SD – standard deviation.</p><p>Demographics and Characteristics of the Twin Sample.</p

Mid- sagittal slice showing tracing of the whole corpus callosum.

<p>Mid- sagittal slice showing tracing of the whole corpus callosum.</p

Intra-class correlations (ICC) estimates for MZ and DZ twin groups for whole CC DTI measures.

<p><u>Notes:</u> MZ – monozygotic twins; DZ- Dizygotic twins; FA – Fractional anisotropy; MD- Mean diffusivity; RD- radial diffusivity; AD – Axial diffusivity; ICC- Intra-class correlations.</p><p>Intra-class correlations (ICC) estimates for MZ and DZ twin groups for whole CC DTI measures.</p

Heritability estimates for Whole CC and its five sub-regions [A-E] for the four DTI measures.

<p>*Values are significant at p<.0001.</p><p><u>Notes</u>: FA – Fractional anisotropy; MD- Mean diffusivity; RD- radial diffusivity; AD – Axial diffusivity; h²- heritability estimate; SE – standard error.</p><p>Heritability estimates for Whole CC and its five sub-regions [A-E] for the four DTI measures.</p