Department of Psychology, College of Science, National Taiwan University, Taipei 10617, Taiwan; Neurobiology and Cognitive Science Center, National Taiwan University, Taipei 10617, Taiwan; Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei 10048, Taiwan; Center for Artificial Intelligence and Advanced Robotics, National Taiwan University, Taipei 10617, Taiwan.
Department of Psychology, College of Science, National Taiwan University, Taipei 10617, Taiwan.
Neuroimage Clin. 2021;30:102626. doi: 10.1016/j.nicl.2021.102626. Epub 2021 Mar 13.
Decreased awareness of memory declines in mild cognitive impairment (MCI) has been linked to structural or functional changes in a wide gray matter network; however, the underlying white matter pathway correlations for the memory awareness deficits remain unknown. Moreover, consistent findings have not been obtained regarding the cognitive basis of disturbed awareness of memory declines in MCI. Due to the methodological drawbacks (e.g., correlational analysis without controlling confounders related to clinical status, a problem related to the representativeness of the control group) of previous studies on the aforementioned topic, further investigation is required. To addressed the research gaps, this study investigated white matter microstructural integrity and the cognitive correlates of memory awareness in 87 older adults with or without mild cognitive impairment (MCI). The patients with MCI and healthy controls (HCs) were divided into two subgroups, namely those with normal awareness (NA) and poor awareness (PA) for memory deficit, according to the discrepancy scores calculated from the differences between subjective and objective memory evaluations. Only the results for HCs with NA (HC-NA) were compared with those for the two MCI groups (i.e., MCI-NA and MCI-PA). The three groups were matched on demographic and clinical variables. An advanced diffusion imaging technique-diffusion spectrum imaging-was used to investigate the integrity of the white matter tract. The results revealed that although the HC-NA group outperformed the two MCI groups on several cognitive tests, the two MCI groups exhibited comparable performance across different neuropsychological tests, except for the test on reasoning ability. Compared with the other two groups, the MCI-PA group exhibited lower integrity in bilateral frontal-striatal fibers, left anterior thalamocortical radiations, and callosal fibers connecting bilateral inferior parietal regions. These results could not be explained by gray matter morphometric differences. Overall, the results indicated that mnemonic anosognosia was not sufficient to explain the memory awareness deficits observed in the patients with MCI. Our brain imaging findings also support the concept of anosognosia for memory deficit as a disconnection syndrome in MCI.
轻度认知障碍（MCI）患者的记忆衰退意识下降与广泛的灰质网络的结构或功能变化有关；然而，记忆意识缺陷的潜在白质通路相关性尚不清楚。此外，对于 MCI 中记忆衰退意识障碍的认知基础，尚未得出一致的发现。由于之前关于上述主题的研究存在方法学上的缺陷（例如，没有控制与临床状态相关的混杂因素的相关性分析，这是与对照组代表性相关的问题），因此需要进一步研究。为了解决研究空白，本研究调查了 87 名患有或不患有轻度认知障碍（MCI）的老年人的白质微观结构完整性和记忆意识的认知相关性。根据主观和客观记忆评估之间的差异计算出差异分数，将 MCI 患者和健康对照组（HC）分为两组，即记忆缺陷的正常意识（NA）和较差意识（PA）组。仅将 HC-NA 组的结果与两个 MCI 组（即 MCI-NA 和 MCI-PA）进行比较。三组在人口统计学和临床变量上相匹配。采用先进的扩散成像技术——弥散张量成像（diffusion spectrum imaging）来研究白质束的完整性。结果表明，尽管 HC-NA 组在多项认知测试中表现优于两个 MCI 组，但两个 MCI 组在不同神经心理学测试中的表现相当，除了推理能力测试外。与其他两组相比，MCI-PA 组在双侧额纹状体纤维、左侧前丘脑皮质辐射和连接双侧下顶叶区域的胼胝体纤维的完整性较低。这些结果不能用灰质形态计量学差异来解释。总体而言，结果表明记忆不自知不足以解释 MCI 患者观察到的记忆意识缺陷。我们的脑成像结果也支持记忆缺陷不自知是 MCI 中的一种断开综合征的概念。
