Yeske Benjamin, Hou Jiancheng, Adluru Nagesh, Nair Veena A, Prabhakaran Vivek
Department of Radiology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States.
Center for Cross-Strait Cultural Development, Fujian Normal University, Fuzhou, China.
Front Aging Neurosci. 2021 Nov 22;13:750621. doi: 10.3389/fnagi.2021.750621. eCollection 2021.
Throughout adulthood, the brain undergoes an array of structural and functional changes during the typical aging process. These changes involve decreased brain volume, reduced synaptic density, and alterations in white matter (WM). Although there have been some previous neuroimaging studies that have measured the ability of adult language production and its correlations to brain function, structural gray matter volume, and functional differences between young and old adults, the structural role of WM in adult language production in individuals across the life span remains to be thoroughly elucidated. This study selected 38 young adults and 35 old adults for diffusion tensor imaging (DTI) and performed the Controlled Oral Word Association Test to assess verbal fluency (VF). Tract-Based Spatial Statistics were employed to evaluate the voxel-based group differences of diffusion metrics for the values of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), and local diffusion homogeneity (LDH) in 12 WM regions of interest associated with language production. To investigate group differences on each DTI metric, an analysis of covariance (ANCOVA) controlling for sex and education level was performed, and the statistical threshold was considered at < 0.00083 (0.05/60 labels) after Bonferroni correction for multiple comparisons. Significant differences in DTI metrics identified in the ANCOVA were used to perform correlation analyses with VF scores. Compared to the old adults, the young adults had significantly (1) increased FA values on the bilateral anterior corona radiata (ACR); (2) decreased MD values on the right ACR, but increased MD on the left uncinate fasciculus (UF); and (3) decreased RD on the bilateral ACR. There were no significant differences between the groups for AD or LDH. Moreover, the old adults had only a significant correlation between the VF score and the MD on the left UF. There were no significant correlations between VF score and DTI metrics in the young adults. This study adds to the growing body of research that WM areas involved in language production are sensitive to aging.
在整个成年期，大脑在典型的衰老过程中会经历一系列结构和功能上的变化。这些变化包括脑容量减小、突触密度降低以及白质（WM）改变。尽管之前有一些神经影像学研究测量了成年人语言产生的能力及其与脑功能、结构灰质体积以及年轻人和老年人之间功能差异的相关性，但WM在整个生命周期个体的成人语言产生中的结构作用仍有待深入阐明。本研究选取了38名年轻成年人和35名老年成年人进行扩散张量成像（DTI），并进行了受控口语单词联想测试以评估言语流畅性（VF）。采用基于纤维束的空间统计学方法，评估与语言产生相关的12个WM感兴趣区域的分数各向异性（FA）、平均扩散率（MD）、轴向扩散率（AD）、径向扩散率（RD）和局部扩散均匀性（LDH）值的基于体素的组间差异。为了研究各DTI指标的组间差异，进行了控制性别和教育水平的协方差分析（ANCOVA），在对多重比较进行Bonferroni校正后，统计阈值设定为<0.00083（0.05/60个标签）。在ANCOVA中确定的DTI指标的显著差异用于与VF分数进行相关性分析。与老年成年人相比，年轻成年人显著表现为：（1）双侧前放射冠（ACR）的FA值增加；（2）右侧ACR的MD值降低，但左侧钩束（UF）的MD值增加；（3）双侧ACR的RD值降低。两组在AD或LDH方面无显著差异。此外，老年成年人中只有VF分数与左侧UF的MD之间存在显著相关性。年轻成年人中VF分数与DTI指标之间无显著相关性。这项研究进一步补充了越来越多的研究成果，即参与语言产生的WM区域对衰老敏感。
