White matter microstructural development and cognitive ability in the first 2 years of life

Abstract

White matter (WM) integrity has been related to cognitive ability in adults and children, but it remains largely unknown how WM maturation in early life supports emergent cognition. The associations between tract‐based measures of fractional anisotropy (FA) and axial and radial diffusivity (AD, RD) shortly after birth, at age 1, and at age 2 and cognitive measures at 1 and 2 years were investigated in 447 healthy infants. We found that generally higher FA and lower AD and RD across many WM tracts in the first year of life were associated with better performance on measures of general cognitive ability, motor, language, and visual reception skills at ages 1 and 2, suggesting an important role for the overall organization, myelination, and microstructural properties of fiber pathways in emergent cognition. RD in particular was consistently related to ability, and protracted development of RD from ages 1 to 2 years in several tracts was associated with higher cognitive scores and better language performance, suggesting prolonged plasticity may confer cognitive benefits during the second year of life. However, we also found that cognition at age 2 was weakly associated with WM properties across infancy in comparison to child and demographic factors including gestational age and maternal education. Our findings suggest that early postnatal WM integrity across the brain is important for infant cognition, though its role in cognitive development should be considered alongside child and demographic factors.

Neonatal White Matter Maturation Is Associated With Infant Language Development

“…Importantly, this study was able to demonstrate that interindividual variation in FA in tracts associated specifically with language function (the CC and left AF) already in neonates is meaningfully associated with language acquisition, despite the fact that major features of this ability are largely absent at birth. This is in line with recent findings by Girault et al (2019), who found that white matter microstructural development in tracts including the AF in newborns was associated with cognitive development as assessed using the Mullen Scales of Early Learning generally, as well as language development as assessed by Mullen Scales of Early Learning subscales specifically. Girault and colleagues chiefly found associations between infant cognitive outcomes and neonatal white matter maturation as assessed by axial diffusivity, a DWI measure assessing longitudinal diffusivity along the tensor ellipsoid Cluster size is indicated by the number of consecutive points in that cluster significantly associated with language outcomes; percentage of tract represents the overall percentage of tract represented by cluster; corrected peak significance in cluster; and beta value at peak significance.…”

“…The maturation of the superior longitudinal fasciculus-AF complex, which connects the inferior frontal gyrus with the superior temporal gyrus/sulci and the inferior parietal lobule, has been shown to correlate with the ability to comprehend complex sentence structures in children aged 3 to 10 years (Skeide et al, 2015). More recently, Girault et al (2019) showed that white matter microstructural development in regions including arcuate tracts at the neonatal time point was associated with receptive language development at 1 and 2 years in healthy children. Both the CC and AF play a role in language processing.…”

“…Higher FA values are assumed to correspond with increased white matter maturity. A diverse set of studies highlight the association between white matter maturation, as measured by FA, and cognitive function in healthy infants and children (e.g., Short et al, 2013;Peters et al, 2014;Stjerna et al, 2015;Girault et al, 2019). In addition, FA in infancy potentially has predictive value for children at risk for adverse cognitive outcomes later in development.…”

Longitudinal associations between white matter maturation and cognitive development across early childhood

“…The nature of the codevelopment of these two longitudinal processes has been of recent interest (Girault et al, 2019;Jolles et al, 2016). The nature of the codevelopment of these two longitudinal processes has been of recent interest (Girault et al, 2019;Jolles et al, 2016).…”

“…There is, however, less known about the time-evolution of the relationship between brain structure and cognitive development, which was the primary motivation for our study. The nature of the codevelopment of these two longitudinal processes has been of recent interest (Girault et al, 2019;Jolles et al, 2016). Previous modeling of the relationship between white matter and cognitive development is sparse and has been cross-sectional (Nagy, Westerberg, & Klingberg, 2004), considered a few age bins (Dubois et al, 2008;Jolles et al, 2016), or used parametric random effects models to provide longitudinal summaries for trajectory clustering .…”