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Early childhood development of white matter fiber density and morphology
NeuroImage ( IF 4.7 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.neuroimage.2020.116552
Dennis Dimond 1 , Christiane S Rohr 2 , Robert E Smith 3 , Thijs Dhollander 4 , Ivy Cho 5 , Catherine Lebel 6 , Deborah Dewey 7 , Alan Connelly 3 , Signe Bray 8
Affiliation  

Early childhood is an important period for cognitive and brain development, though white matter changes specific to this period remain understudied. Here we utilize a novel analytic approach to quantify and track developmental changes in white matter micro- and macro-structure, calculated from individually oriented fiber-bundle populations, termed "fixels". Fixel-based analysis and mixed-effects models were used to assess tract-wise changes in fiber density and bundle morphology in 73 girls scanned at baseline (ages 4.09-7.02, mean = 5.47, SD = 0.81), 6-month (N = 7), and one-year follow-up (N = 42). For comparison, we also assessed changes in commonly utilized diffusion tensor metrics: fractional anisotropy (FA), and mean, radial and axial diffusivity (MD, RD, AD). Maturational increases in fixel-metrics were seen in most major white matter tracts, with the most rapid increases in the corticospinal tract and slowest or non-significant increases in the genu of the corpus callosum and uncinate fasciculi. As expected, we observed developmental increases in FA and decreases in MD, RD and AD, though percentage changes were smaller relative to fixel-metrics. The majority of tracts showed more substantial morphological than microstructural changes. These findings highlight early childhood as a period of dynamic white matter maturation, characterized by large increases in macroscopic fiber bundle size, mild changes in axonal density, and parallel, albeit less substantial, changes in diffusion tensor metrics.

中文翻译:

白质纤维密度和形态学早期发育

幼儿期是认知和大脑发育的重要时期,尽管这一时期特有的白质变化仍未得到充分研究。在这里,我们利用一种新的分析方法来量化和跟踪白质微观和宏观结构的发育变化,从单独定向的纤维束种群计算,称为“固定素”。基于 Fixel 的分析和混合效应模型用于评估 73 名在基线(4.09-7.02 岁,平均值 = 5.47,SD = 0.81)、6 个月(N = 7)和一年的随访(N = 42)。为了进行比较,我们还评估了常用扩散张量指标的变化:各向异性分数 (FA) 以及平均、径向和轴向扩散率 (MD、RD、AD)。在大多数主要白质束中观察到固定素指标的成熟增加,皮质脊髓束增加最快,胼胝体和钩状束的膝部增加最慢或不显着。正如预期的那样,我们观察到 FA 的发育增加和 MD、RD 和 AD 的减少,尽管百分比变化相对于 fixel-metrics 较小。大多数大片显示出比微观结构更显着的形态变化。这些发现强调了幼儿期是一个动态白质成熟时期,其特征是宏观纤维束大小大幅增加,轴突密度发生轻微变化,以及扩散张量指标的平行变化,尽管不那么显着。皮质脊髓束的增加最迅速,胼胝体和钩状束的膝部增加最慢或不显着。正如预期的那样,我们观察到 FA 的发育增加和 MD、RD 和 AD 的减少,尽管百分比变化相对于 fixel-metrics 较小。大多数大片显示出比微观结构更显着的形态变化。这些发现强调了幼儿期是一个动态白质成熟时期,其特征是宏观纤维束大小大幅增加,轴突密度发生轻微变化,以及扩散张量指标的平行变化,尽管不那么显着。皮质脊髓束的增加最迅速,胼胝体和钩状束的膝部增加最慢或不显着。正如预期的那样,我们观察到 FA 的发育增加和 MD、RD 和 AD 的减少,尽管百分比变化相对于 fixel-metrics 较小。大多数大片显示出比微观结构更显着的形态变化。这些发现强调了儿童早期是一个动态白质成熟时期,其特征是宏观纤维束大小大幅增加,轴突密度发生轻微变化,以及扩散张量指标的平行变化(尽管不那么显着)。尽管相对于 fixel-metrics 的百分比变化较小。大多数大片显示出比微观结构更显着的形态变化。这些发现强调了幼儿期是一个动态白质成熟时期,其特征是宏观纤维束大小大幅增加,轴突密度发生轻微变化,以及扩散张量指标的平行变化,尽管不那么显着。尽管相对于 fixel-metrics 的百分比变化较小。大多数大片显示出比微观结构更显着的形态变化。这些发现强调了幼儿期是一个动态白质成熟时期,其特征是宏观纤维束大小大幅增加,轴突密度发生轻微变化,以及扩散张量指标的平行变化,尽管不那么显着。
更新日期:2020-04-01
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