Abstract
A fundamental task in neuroscience is to characterize the brain's developmental course. While replicable group-level models of structural brain development from childhood to adulthood have recently been identified, we have yet to quantify and understand individual differences in structural brain development. The present study examined inter-individual variability and sex differences in changes in brain structure, as assessed by anatomical MRI, across ages 8.0–26.0 years in 269 participants (149 females) with three time points of data (807 scans), drawn from three longitudinal datasets collected in the Netherlands, Norway, and USA. We further investigated the relationship between overall brain size and developmental changes, as well as how females and males differed in change variability across development. There was considerable inter-individual variability in the magnitude of changes observed for all examined brain measures. The majority of individuals demonstrated decreases in total gray matter volume, cortex volume, mean cortical thickness, and white matter surface area in mid-adolescence, with more variability present during the transition into adolescence and the transition into early adulthood. While most individuals demonstrated increases in white matter volume in early adolescence, this shifted to a majority demonstrating stability starting in mid-to-late adolescence. We observed sex differences in these patterns, and also an association between the size of an individual's brain structure and the overall rate of change for the structure. The present study provides new insight as to the amount of individual variance in changes in structural morphometrics from late childhood to early adulthood in order to obtain a more nuanced picture of brain development. The observed individual- and sex-differences in brain changes also highlight the importance of further studying individual variation in developmental patterns in healthy, at-risk, and clinical populations.
Highlights
Longitudinal MRI research conducted over the past two decades has demonstrated that the human brain undergoes a prolonged course of development, with changes in morphometry observed in the cortex, as well as in white matter and subcortical structures, throughout childhood and adolescence (Aubert-Broche et al, 2013; Goddings et al, 2013; Lebel and Beaulieu, 2011; Mutlu et al, 2013; Raznahan et al, 2011; Reynolds et al, 2019; Vijayakumar et al, 2016; Wierenga et al, 2014a,b; Wierenga, Bos, et al, 2018)
The present study demonstrates that individuals vary in the direction and magnitude of structural brain changes across late childhood into young adulthood
The greatest interindividual variability in the direction of change was observed during transition periods into adolescence and into early adulthood
Summary
Longitudinal MRI research conducted over the past two decades has demonstrated that the human brain undergoes a prolonged course of development, with changes in morphometry observed in the cortex, as well as in white matter and subcortical structures, throughout childhood and adolescence (Aubert-Broche et al, 2013; Goddings et al, 2013; Lebel and Beaulieu, 2011; Mutlu et al, 2013; Raznahan et al, 2011; Reynolds et al, 2019; Vijayakumar et al, 2016; Wierenga et al, 2014a,b; Wierenga, Bos, et al, 2018). While this research has had a profound impact on our understanding of brain development, most of these studies have focused on estimating group-level trajectories, and quantifying the degree of individual variability in structural brain development remains a neglected area of research (Becht and Mills, 2020). Characterizing variability across individuals in how the brain changes during development is needed to address some of the most pressing questions in developmental neuroscience. For instance, the cerebral cortex decreases in volume and thickness across the second decade of life before be-
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