Boespflug Erin L, Storrs Judd, Sadat-Hossieny Sara, Eliassen James, Shidler Marcelle, Norris Matthew, Krikorian Robert
Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati Academic Health Center, PO Box 670559, Cincinnati, OH, 45267-0559, USA,
Brain Struct Funct. 2014 Jan;219(1):367-79. doi: 10.1007/s00429-013-0506-x. Epub 2013 Jan 24.
Diffusion tensor imaging (DTI) is used to detect tissue pathology. In Alzheimer's disease (AD) research, DTI has been used to elucidate differences in disease stages and to track progression over time and clinical severity. Many of these studies have identified the fornix as particularly vulnerable in the early stages of pathology associated with memory decline in prodromal AD. Emerging research suggests principal tensor components, axial (DA) and radial (DR) diffusivity, are more sensitive to underlying tissue pathology than are mean diffusivity (MD) and fractional anisotropy (FA). Given the established regionally specific tissue decline in MCI, we examined components of the full diffusion tensor (MD, FA, DR, and DA) for sensitivity to regional pathology associated with specific memory deficits in 18 individuals with MCI. We investigated multiple regions of interest, including fornix, temporal stem, and control regions for association with severity of impairment on multiple memory measures, including a type of neuropsychological task shown to be particularly sensitive to early memory decline in MCI. Better paired associate learning was selectively associated with lower DA (β = -0.663, p = 0.003), but not with DR, MD, or FA of the temporal stems. Conversely, better paired associate learning was associated with lower DR (β = -0.523, p = 0.026), higher FA (β = 0.498, p = 0.036), and lower MD (β = -0.513, p = 0.030), but not DA in the fornix. No association was found for control regions, or for control cognitive measures. These findings suggest disparate pathology of temporal stems and fornix white matter in association with early memory impairment in MCI. Further, they highlight the methodological importance of evaluating the full tensor, rather than only summative metrics in research using DTI.
扩散张量成像（DTI）用于检测组织病理学变化。在阿尔茨海默病（AD）研究中，DTI已被用于阐明疾病阶段的差异，并追踪疾病随时间的进展以及临床严重程度。许多此类研究已确定，在与前驱期AD记忆衰退相关的病理学早期阶段，穹窿特别脆弱。新出现的研究表明，张量主成分、轴向扩散率（DA）和径向扩散率（DR）比平均扩散率（MD）和分数各向异性（FA）对潜在的组织病理学变化更敏感。鉴于轻度认知障碍（MCI）中已确定存在区域特异性组织衰退，我们检查了18名MCI患者全扩散张量的各成分（MD、FA、DR和DA），以确定其对与特定记忆缺陷相关的区域病理学变化的敏感性。我们研究了多个感兴趣区域，包括穹窿、颞叶干以及对照区域，以确定它们与多种记忆测量指标的损伤严重程度之间的关联，这些测量指标包括一种对MCI早期记忆衰退特别敏感的神经心理学任务类型。更好的配对联想学习与颞叶干较低的DA（β = -0.663，p = 0.003）有选择性关联，但与DR、MD或FA无关。相反，更好的配对联想学习与穹窿较低的DR（β = -0.523，p = 0.026）、较高的FA（β = 0.498，p = 0.036）和较低的MD（β = -0.513，p = 0.030）有选择性关联，但与DA无关。在对照区域或对照认知测量中未发现关联。这些发现表明，MCI早期记忆障碍与颞叶干和穹窿白质的不同病理学变化有关。此外，它们凸显了在使用DTI的研究中评估全张量而非仅评估汇总指标的方法学重要性。
