Age-related differences in white matter tract microstructure are associated with cognitive performance from childhood to adulthood.

Background: Age-related differences in white matter tract microstructure have been well established across the life span. In the present cross-sectional study, we examined whether these differences are associated with neurocognitive performance from childhood to late adulthood.

Methods: Diffusion tensor imaging was performed in 296 healthy subjects aged 8 to 68 years (mean = 29.6, SD = 14.6). The corpus callosum, two projection tracts, and five association tracts were traced using probabilistic tractography. A neurocognitive test battery was used to assess speed of processing, attention, spatial working memory, verbal functioning, visual learning, and executive functioning. Linear mediation models were used to examine whether differences in white matter tract fractional anisotropy (FA) were associated with neurocognitive performance, independent of the effect of age.

Results: From childhood to early adulthood, higher FA of the cingulum bundle and inferior frontooccipital fasciculus (IFOF) was associated with higher executive functioning and global cognitive functioning, respectively, independent of the effect of age. When adjusting for speed of processing, FA of the IFOF was no longer associated with performance in the other cognitive domains with the exception of visual learning. From early adulthood to late adulthood, white matter tract FA was not associated with cognitive performance independent of the age effect.

Conclusions: The cingulum bundle may play a critical role in protracted maturation of executive functioning. The IFOF may play a key role in maturation of visual learning and may act as a central "hub" in global cognitive maturation by subserving maturation of processing speed.