Table 1.
Sample characteristics of the full sample (left) and of the subset of children for which longitudinal data was available (right).
Figure 1.
Significant tissue expansion: Significant Jacobian values > 1 overlaid on the model brain.
Values range from 1.02 (purple) to 1.30 (bright red). Expansion was observed in regions covering the arcuate fasciculus (E), cerebellar penduncle (A), cinguli (C) , corpus callosum (B,C), cortical spinal tract (B,F), uncinate fasciculus (D) and on the gray matter / cerebral spinal fluid boundary (A-F), the latter likely representing brain growth. For visualization purposes, values were resampled to model brain resolution.
Table 2.
Fractional anisotropy in 9 and 12 year old children.
Figure 2.
Increases of relative fractional anisotropy between the ages of 9 and 12, projected onto the group average fiber bundle.
Left, top and right view. For visualization purposes, values were smoothed along the bundle using LOESS [59].
Table 3.
Longitudinal diffusivity (λ1; x 10−3 mm2/s) in 9 and 12 year old children.
Table 4.
Radial diffusivity (λ23; ×10–3 mm2/s) in 9 and 12 year old children.
Figure 3.
The relationship between changes in pure white matter fractional anisotropy and changes in white matter volume in the three-year interval.
Figure 4.
Relative white matter surface area expansion of AAL regions in the left and right hemisphere.
Please note that expansion is based (and projected on) AAL regions rather than representing continuous expansion. *Areas in which girls had larger expansion than boys.
Table 5.
Heritability and unique environmental influences for white matter volume, mean fractional anisotropy in pure white matter, white matter surface area and fractional anisotropy in fiber bundles at ages 9 and 12.
Figure 5.
Histograms of fractional anisotropy in pure white matter at age 9 and age 12.
In the 14 children with relatively large volumetric white matter growth mean fractional anisotropy was 0.43 at both ages. In 13 children with relatively small volumetric white matter growth, mean fractional anisotropy increased from 0.41 to 0.44.