Longitudinal characterization of white matter maturation during adolescence

Abstract

Background: Late adolescence is comprised of considerable developmental transitions, though brain maturational changes during this period are subtle and difficult to quantitatively evaluate from standard brain imaging acquisitions. To date, primarily cross-sectional studies have characterized typical developmental changes during adolescence, but these processes need further description within a longitudinal framework.

Method: To assess the developmental trajectory of typical white matter development, we examined 22 healthy adolescents with serial diffusion tensor images (DTI) collected at a mean age of 17.8 years and 16-months later. Diffusion parameters fractional anisotropy, and mean, radial, and axial diffusivity were subjected to whole-brain voxelwise time point comparisons using tract-based spatial statistics.

Results: At follow-up, adolescents showed a significant change (>or=153 contiguous voxels each at p<0.01) in diffusion properties, including in bilateral superior longitudinal fasciculi, superior corona radiata, anterior thalamic radiations, and posterior limb of the internal capsule. Overall, correlations with cognitive performances suggested behavioral improvement corresponding with white matter changes.

Conclusion: These longitudinal DTI findings support continued microstructural change in white matter during late adolescence, and suggest ongoing refinement of projection and association fibers into early adulthood.

Figure 1

Clusters of significant change (≥ 153 μl, p<0.01) in the: (A) superior longitudinal fasciculus (right = red; left = orange), and superior corona radiata (yellow); (B) right thalamic fibers (green); and (C) right posterior limb of the internal capsule (cyan) and superior longitudinal fasciculus (red) from Time 1 to Time 2 in adolescents (N=22). Results are superimposed on the fiber skeleton (blue) and overlaid on a standardized FA template. Images are in radiological convention.

Figure 2

Overlapping regions of significant change in fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) from Time 1 to Time 2 among adolescents (N=22). Increased FA in the thalamic radiations, superior longitudinal fasciculus and posterior limb of the internal capsule was associated with an equal or greater decrease in RD over time. Abbreviations. ATR = Anterior thalamic radiations; SLF = Superior longitudinal fasciculus; PLIC = Posterior limb of internal capsule; SCR = Superior corona radiata; IFOF = Inferior fronto-occipital fasciculus; CF = Cerebellar fibers; R = Right; L = Left.