Head Denise, Buckner Randy L, Shimony Joshua S, Williams Laura E, Akbudak Erbil, Conturo Thomas E, McAvoy Mark, Morris John C, Snyder Abraham Z
Howard Hughes Medical Institute, Washington University, St Louis, MO 63130, USA.
Cereb Cortex. 2004 Apr;14(4):410-23. doi: 10.1093/cercor/bhh003.
White matter microstructural integrity was assessed using diffusion tensor imaging (DTI) in 25 young adults, 25 nondemented older adults, and 25 age-matched older adults with dementia of the Alzheimer type (DAT). For each individual, measures of anisotropy and diffusivity were obtained from atlas-transformed images in the anterior and posterior callosum and in the frontal, parietal, temporal and occipital white matter. These data revealed age differences in anisotropy and diffusivity in all assessed regions. Age effects were greater in the anterior as opposed to the posterior corpus callosum and greater in the frontal white matter than in the temporal, parietal and occipital white matter, suggesting age-associated differences in white matter that exhibit a roughly anterior-to-posterior gradient. In contrast, individuals with early-stage dementia exhibited minimal, if any, additional change in anterior regions but did show greater deterioration of white matter in posterior lobar regions. Taken collectively, these results indicate that nondemented aging is characterized by significant changes in white matter most prominently in anterior brain regions. The dissociation between the regional effects of age and dementia status suggests that the mechanisms underlying age-associated cognitive decline are likely distinct from those underlying DAT.
使用扩散张量成像（DTI）对25名年轻成年人、25名无痴呆的老年人以及25名年龄匹配的患有阿尔茨海默病型痴呆（DAT）的老年人的白质微观结构完整性进行了评估。对于每个个体，从胼胝体前后部以及额叶、顶叶、颞叶和枕叶白质的图谱转换图像中获取各向异性和扩散率的测量值。这些数据揭示了所有评估区域中各向异性和扩散率的年龄差异。与胼胝体后部相比，胼胝体前部的年龄效应更大，额叶白质中的年龄效应大于颞叶、顶叶和枕叶白质，这表明白质中与年龄相关的差异呈现出大致从前到后的梯度。相比之下，早期痴呆患者在前部区域即使有变化也极小，但在后叶区域确实表现出更严重的白质退化。总体而言，这些结果表明，无痴呆的衰老特征是白质发生显著变化，最明显的是在前脑区域。年龄和痴呆状态的区域效应之间的分离表明，与年龄相关的认知衰退的潜在机制可能与DAT的潜在机制不同。
