Developmental Imaging, Murdoch Children's Research Institute, Parkville, Australia; Department of Paediatrics, University of Melbourne, Parkville, Australia.
The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia; Department of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia.
Neuroimage. 2018 Dec;183:666-676. doi: 10.1016/j.neuroimage.2018.08.043. Epub 2018 Aug 22.
White matter fibre development in childhood involves dynamic changes to microstructural organisation driven by increasing axon diameter, density, and myelination. However, there is a lack of longitudinal studies that have quantified advanced diffusion metrics to identify regions of accelerated fibre maturation, particularly across the early pubertal period. We applied a novel longitudinal fixel-based analysis (FBA) framework, in order to estimate microscopic and macroscopic white matter changes over time.
Diffusion-weighted imaging (DWI) data were acquired for 59 typically developing children (27 female) aged 9-13 years at two time-points approximately 16 months apart (time-point 1: 10.4 ± 0.4 years, time-point 2: 11.7 ± 0.5 years). Whole brain FBA was performed using the connectivity-based fixel enhancement method, to assess longitudinal changes in fibre microscopic density and macroscopic morphological measures, and how these changes are related to sex, pubertal stage, and pubertal progression. Follow-up analyses were performed in sub-regions of the corpus callosum to confirm the main findings using a Bayesian repeated measures approach.
There was a statistically significant increase in fibre density over time localised to medial and posterior commissural and association fibres, including the forceps major and bilateral superior longitudinal fasciculus. Increases in fibre cross-section were substantially more widespread. The rate of fibre development was not associated with age or sex. In addition, there was no significant relationship between pubertal stage or progression and longitudinal fibre development over time. Follow-up Bayesian analyses were performed to confirm the findings, which supported the null effect of the longitudinal pubertal comparison.
Using a novel longitudinal fixel-based analysis framework, we demonstrate that white matter fibre density and fibre cross-section increased within a 16-month scan rescan period in specific regions. The observed increases might reflect increasing axonal diameter or axon count. Pubertal stage or progression did not influence the rate of fibre development in the early stages of puberty. Future work should focus on quantifying these measures across a wider age range to capture the full spectrum of fibre development across the pubertal period.
儿童期白质纤维的发育涉及微观结构组织的动态变化，这些变化由轴突直径、密度和髓鞘形成的增加驱动。然而，缺乏对量化先进扩散指标的纵向研究，以确定纤维成熟加速的区域，特别是在青春期早期。我们应用了一种新的纵向固定元分析（FBA）框架，以随时间估计微观和宏观白质变化。
为 59 名年龄在 9 至 13 岁之间的典型发育儿童（27 名女性）采集扩散加权成像（DWI）数据，两次采集时间间隔约为 16 个月（时间点 1：10.4±0.4 岁，时间点 2：11.7±0.5 岁）。使用基于连接的固定元增强方法进行全脑 FBA，以评估纤维微观密度和宏观形态学测量的纵向变化，以及这些变化如何与性别、青春期阶段和青春期进展相关。在胼胝体的子区域中进行了随访分析，以使用贝叶斯重复测量方法确认主要发现。
在时间上，纤维密度的增加具有统计学意义，定位于内侧和后连合纤维以及联合纤维，包括主要内囊和双侧上纵束。纤维横截面的增加要广泛得多。纤维发育的速度与年龄或性别无关。此外，青春期阶段或进展与随时间的纵向纤维发育之间没有显著关系。进行了后续的贝叶斯分析以确认这些发现，这些发现支持纵向青春期比较的无效假设。
使用新的纵向固定元分析框架，我们证明了在 16 个月的扫描再扫描期间，特定区域的白质纤维密度和纤维横截面增加。观察到的增加可能反映了轴突直径或轴突数量的增加。青春期阶段或进展并没有影响青春期早期纤维发育的速度。未来的工作应该集中在跨更广泛的年龄范围量化这些措施，以捕获整个青春期纤维发育的全貌。
