Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095-1763, USA.
Brain Res. 2013 May 28;1512:22-36. doi: 10.1016/j.brainres.2013.03.028. Epub 2013 Mar 30.
White matter integrity changes with age, with the extent of variation dependent on attributes such as sex and oligodendrocyte health. Quantification of myelin and axonal integrity in healthy people would provide normative values necessary to determine pathology-related tissue characteristics with normal-aging and gender. We assessed white matter integrity with diffusion tensor imaging-based axial and radial diffusivity procedures (3.0-Tesla magnetic resonance imaging), which measure water diffusion parallel and perpendicular to axonal bundles, indicating axonal and myelin status, respectively, using region-of-interest (ROI) analyses, in 34 healthy adults (age, 46.5 ± 6.0 years, 19 male). Sex differences in diffusion values were assessed with two-sample t-tests, and diffusion changes with age using Pearson's correlations; whole-brain effect sizes were examined with voxel-based procedures. Multiple brain areas showed increased axial and radial diffusivity values reflecting declines in axonal and myelin integrity with age, especially in mid-hippocampal and posterior thalamic areas. However, axonal and myelin integrity increased in insular and occipital cortex projections with maturity. Females showed reduced fiber and myelin integrity in substantially more structures than males, and those areas included limbic, basal ganglia, pontine, and cerebellar sites. A minority of structures, confined to cerebellar, temporal, and frontal cortices, showed reduced fiber and myelin integrity with age in males over females. Whole-brain effect sizes in diffusion values between sexes and age-related changes showed findings parallel to ROI analyses. The structural differences mandate partitioning of sex and age in adult white matter pathology assessment, and likely contribute to sex-based physiological and behavioral dysfunction in aging and in multiple pathologies.
白质完整性随年龄变化，其变化程度取决于性别和少突胶质细胞健康等属性。在健康人群中量化髓鞘和轴突完整性，将为确定与正常衰老和性别相关的组织特征提供与病理学相关的必要规范值。我们使用基于扩散张量成像的轴向和径向扩散程序（3.0T 磁共振成像）评估白质完整性，这些程序分别测量水在轴突束平行和垂直方向上的扩散，以指示轴突和髓鞘状态，使用感兴趣区域（ROI）分析，对 34 名健康成年人（年龄 46.5 ± 6.0 岁，19 名男性）进行了评估。使用两样本 t 检验评估扩散值的性别差异，并使用 Pearson 相关性评估扩散随年龄的变化；使用体素分析检查全脑效应大小。多个大脑区域显示出轴向和径向扩散值增加，反映了随着年龄的增长轴突和髓鞘完整性的下降，尤其是在中海马和后丘脑区域。然而，随着成熟，岛叶和枕叶皮质的投射区的轴突和髓鞘完整性增加。女性比男性在更多的结构中表现出纤维和髓鞘完整性降低，这些区域包括边缘系统、基底神经节、脑桥和小脑部位。少数结构，仅限于小脑、颞叶和额叶皮质，在男性中显示出随年龄增长纤维和髓鞘完整性降低，而在女性中则没有。性别间和年龄相关的扩散值全脑效应大小显示出与 ROI 分析平行的发现。这些结构差异要求在成人白质病理学评估中划分性别和年龄，并且可能导致衰老和多种病理中基于性别的生理和行为功能障碍。
