Dickerson Bradford C, Feczko Eric, Augustinack Jean C, Pacheco Jenni, Morris John C, Fischl Bruce, Buckner Randy L
Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
Neurobiol Aging. 2009 Mar;30(3):432-40. doi: 10.1016/j.neurobiolaging.2007.07.022. Epub 2007 Sep 14.
The volume of parcellated cortical regions is a composite measure related to both thickness and surface area. It is not clear whether volumetric decreases in medial temporal lobe (MTL) cortical regions in aging and Alzheimer's disease (AD) are due to thinning, loss of surface area, or both, nor is it clear whether aging and AD differ in their effects on these properties. Participants included 28 Younger Normals, 47 Older Normals, and 29 patients with mild AD. T1-weighted MRI data were analyzed using a novel semi-automated protocol (presented in a companion article) to delineate the boundaries of entorhinal (ERC), perirhinal (PRC), and posterior parahippocampal (PPHC) cortical regions and calculate their mean thickness, surface area, and volume. Compared to Younger Normals, Older Normals demonstrated moderately reduced ERC and PPHC volumes, which were due primarily to reduced surface area. In contrast, the expected AD-related reduction in ERC volume was produced by a large reduction in thickness with minimal additional effect (beyond that of aging) on surface area. PRC and PPHC also showed large AD-related reductions in thickness. Of all these MTL morphometric measures, ERC and PRC thinning were the best predictors of poorer episodic memory performance in AD. Although the volumes of MTL cortical regions may decrease with both aging and AD, thickness is relatively preserved in normal aging, while even in its mild clinical stage, AD is associated with a large degree of thinning of MTL cortex. These differential morphometric effects of aging and AD may reflect distinct biologic processes and ultimately may provide insights into the anatomic substrates of change in memory-related functions of MTL cortex.
大脑皮质分区区域的体积是一种与厚度和表面积相关的综合测量指标。目前尚不清楚在衰老和阿尔茨海默病（AD）中，内侧颞叶（MTL）皮质区域的体积减小是由于变薄、表面积减少还是两者兼而有之，也不清楚衰老和AD对这些特性的影响是否存在差异。研究参与者包括28名年轻正常人、47名老年正常人以及29名轻度AD患者。使用一种新颖的半自动方案（在一篇配套文章中介绍）对T1加权MRI数据进行分析，以勾勒内嗅皮质（ERC）、嗅周皮质（PRC）和海马旁后皮质（PPHC）区域的边界，并计算它们的平均厚度、表面积和体积。与年轻正常人相比，老年正常人的ERC和PPHC体积有中度减小，这主要是由于表面积减小所致。相比之下，AD相关的ERC体积减小主要是由于厚度大幅减小，而表面积的额外影响（超出衰老的影响）最小。PRC和PPHC的厚度在AD中也有大幅减小。在所有这些MTL形态测量指标中，ERC和PRC变薄是AD患者情景记忆表现较差的最佳预测指标。尽管MTL皮质区域的体积可能会随着衰老和AD而减小，但在正常衰老过程中厚度相对保持不变，而即使在轻度临床阶段，AD也与MTL皮质的大量变薄有关。衰老和AD的这些不同形态测量效应可能反映了不同的生物学过程，并最终可能为MTL皮质记忆相关功能变化的解剖学基础提供见解。
