Department of Psychology, Center for the Study of Human Cognition, University of Oslo, Blindern, 0317 Oslo, Norway.
Cereb Cortex. 2010 Sep;20(9):2055-68. doi: 10.1093/cercor/bhp280. Epub 2009 Dec 23.
Magnetic resonance imaging volumetry studies report inverted U-patterns with increasing white-matter (WM) volume into middle age suggesting protracted WM maturation compared with the cortical gray matter. Diffusion tensor imaging (DTI) is sensitive to degree and direction of water permeability in biological tissues, providing in vivo indices of WM microstructure. The aim of this cross-sectional study was to delineate age trajectories of WM volume and DTI indices in 430 healthy subjects ranging 8-85 years of age. We used automated regional brain volume segmentation and tract-based statistics of fractional anisotropy, mean, and radial diffusivity as markers of WM integrity. Nonparametric regressions were used to fit the age trajectories and to estimate the timing of maximum development and deterioration in aging. Although the volumetric data supported protracted growth into the sixth decade, DTI indices plateaued early in the fourth decade across all tested regions and then declined slowly into late adulthood followed by an accelerating decrease in senescence. Tractwise and voxel-based analyses yielded regional differences in development and aging but did not provide ample evidence in support of a simple last-in-first-out hypothesis of life-span changes.
磁共振成像容积研究报告显示，从中年开始，白质（WM）体积呈倒 U 型增加，这表明与皮质灰质相比，WM 成熟过程更为漫长。弥散张量成像（DTI）对生物组织中水分子渗透性的程度和方向敏感，提供了 WM 微观结构的活体指标。本横断面研究旨在描绘 430 名健康受试者（年龄 8-85 岁）的 WM 体积和 DTI 指数的年龄轨迹。我们使用自动区域脑容量分割和基于束的各向异性、平均值和径向弥散度的统计方法作为 WM 完整性的标志物。非参数回归用于拟合年龄轨迹，并估计在衰老过程中 WM 发育和衰退的最大时间。尽管体积数据支持进入第六个十年的持续增长，但 DTI 指数在第四个十年早期在所有测试区域达到平台期，然后在老年期缓慢下降，随后在衰老期加速下降。束状和体素分析显示出在发育和衰老方面存在区域差异，但没有提供充分的证据支持寿命变化的简单后进先出假说。
