Department of Gerontology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China.
CNS Neurosci Ther. 2021 May;27(5):587-602. doi: 10.1111/cns.13621. Epub 2021 Mar 2.
Mild cognitive impairment due to semantic dementia represents the preclinical stage, involving cognitive decline dominated by semantic impairment below the semantic dementia standard. Therefore, studying mild cognitive impairment due to semantic dementia may identify changes in patients before progression to dementia. However, whether changes in local functional activity occur in preclinical stages of semantic dementia remains unknown. Here, we explored local functional changes in patients with mild cognitive impairment due to semantic dementia using resting-state functional MRI.
We administered a battery of neuropsychological tests to twenty-two patients with mild cognitive impairment due to semantic dementia (MCI-SD group) and nineteen healthy controls (HC group). We performed structural MRI to compare gray matter volumes, and resting-state functional MRI with multiple sub-bands and indicators to evaluate functional activity.
Neuropsychological tests revealed a significant decline in semantic performance in the MCI-SD group, but no decline in other cognitive domains. Resting-state functional MRI revealed local functional changes in multiple brain regions in the MCI-SD group, distributed in different sub-bands and indicators. In the normal band, local functional changes were only in the gray matter atrophic area. In the other sub-bands, more regions with local functional changes outside atrophic areas were found across various indicators. Among these, the degree centrality of the left precuneus in the MCI-SD group was positively correlated with general semantic tasks (oral sound naming, word-picture verification).
Our study revealed local functional changes in mild cognitive impairment due to semantic dementia, some of which were located outside the atrophic gray matter. Driven by functional connectivity changes, the left precuneus might play a role in preclinical semantic dementia. The study proved the value of frequency-dependent sub-bands, especially the slow-2 and slow-3 sub-bands.
语义性痴呆导致的轻度认知障碍代表了临床前阶段，涉及以语义障碍为主的认知下降，低于语义性痴呆的标准。因此，研究语义性痴呆导致的轻度认知障碍可能会在患者进展为痴呆之前发现他们的变化。然而，语义性痴呆的临床前阶段是否会发生局部功能活动的变化尚不清楚。在这里，我们使用静息态功能磁共振成像研究了语义性痴呆导致的轻度认知障碍患者的局部功能变化。
我们对 22 名语义性痴呆导致的轻度认知障碍患者（MCI-SD 组）和 19 名健康对照者（HC 组）进行了一系列神经心理学测试。我们进行了结构磁共振成像以比较灰质体积，并使用多子带和指标进行静息态功能磁共振成像以评估功能活动。
神经心理学测试显示 MCI-SD 组在语义表现方面有显著下降，但其他认知领域没有下降。静息态功能磁共振成像显示 MCI-SD 组多个脑区存在局部功能变化，分布在不同的子带和指标中。在正常带，局部功能变化仅出现在灰质萎缩区域。在其他子带中，在各种指标下，在萎缩区域之外发现了更多具有局部功能变化的区域。其中，MCI-SD 组左侧楔前叶的度中心度与一般语义任务（口头发音命名、单词-图片验证）呈正相关。
我们的研究揭示了语义性痴呆导致的轻度认知障碍的局部功能变化，其中一些位于萎缩灰质之外。在功能连接变化的驱动下，左侧楔前叶可能在语义性痴呆的临床前阶段发挥作用。该研究证明了频率相关子带的价值，特别是慢-2 子带和慢-3 子带。
