Longitudinal Development of Human Brain Wiring Continues from Childhood into Adulthood

Abstract

Healthy human brain development is a complex process that continues during childhood and adolescence, as demonstrated by many cross-sectional and several longitudinal studies. However, whether these changes end in adolescence is not clear. We examined longitudinal white matter maturation using diffusion tensor tractography in 103 healthy subjects aged 5-32 years; each volunteer was scanned at least twice, with 221 total scans. Fractional anisotropy (FA) and mean diffusivity (MD), parameters indicative of factors including myelination and axon density, were assessed in 10 major white matter tracts. All tracts showed significant nonlinear development trajectories for FA and MD. Significant within-subject changes occurred in the vast majority of children and early adolescents, and these changes were mostly complete by late adolescence for projection and commissural tracts. However, association tracts demonstrated postadolescent within-subject maturation of both FA and MD. Diffusion parameter changes were due primarily to decreasing perpendicular diffusivity, although increasing parallel diffusivity contributed to the prolonged increases of FA in association tracts. Volume increased significantly with age for most tracts, and longitudinal measures also demonstrated postadolescent volume increases in several association tracts. As volume increases were not directly associated with either elevated FA or reduced MD between scans, the observed diffusion parameter changes likely reflect microstructural maturation of brain white matter tracts rather than just gross anatomy.

Age at First Exposure to Football Is Associated with Altered Corpus Callosum White Matter Microstructure in Former Professional Football Players

“…34,65,66,70 The genu and splenium reach 90% of peak FA by age 11, 34 followed by a much slower increase in FA until peak levels are reached in the early 20s. 34,64,65 Snook and colleagues 66 showed a greater slope of increase in FA in the genu than in the splenium between ages 8-12, suggesting greater anterior CC development during this time. The genu and anterior midbody of the CC contain small-diameter, lightly-myelinated fibers, and the genu has the highest proportion of unmyelinated fibers in the adult CC.…”

“…26,[60][61][62][63] Key aspects of CC development, including high rates of myelination and axonal growth, occur between ages 8-12. 34,[64][65][66] However, the relationship between RHI experienced during this critical neurodevelopmental period and later-life CC microstructure has not been examined.…”

The importance of early conscientiousness for socio-economic outcomes: evidence from the British Cohort Study

“…We consider a child's cognitive ability. We construct a measure using test scores at age 10 because cognitive ability seems to be set at that age in the sense that it is rank-order stable (e.g., Lebel and Beaulieu, 2011 School performance, the home environment a child grew up in, social skills as a child, and final education and occupation are also measured. These other measures are used alongside the Big Five personality measures to estimate the effects of personality on outcomes, and are introduced and discussed in Section 3.…”

“…We construct a measure using test scores at age 10 because cognitive ability seems to be set at that age (e.g., Lebel and Beaulieu, 2011 "During the past year, which of the following sports did you play when they were in season?" Count of sports indicated to have played in school in the past year Sports outside school "During the past year, which of the following sports did you play when they were in season?"…”

“…The outcomes are adult wages, saving behaviour, indicators of 1 See e.g., Cunha et al (2006), Knudsen et al (2006), Heckman (2007), Borghans et al (2008a), Roberts (2009), Dohmen et al (2010), Almlund et al (2011), Lebel and Beaulieu (2011) and Moffitt et al (2011). 2 See and Jackson et al (2009) for meta-analyses with conscientiousness as a predictor for outcomes.…”