Abstract

Background:

Semantic memory impairments in semantic dementia are attributed to atrophy and functional disruption of the anterior temporal lobes. In contrast, the posterior medial temporal neurodegeneration found in Alzheimer’s disease is associated with episodic memory disturbance. The two dementia subtypes share hippocampal deterioration, despite a relatively spared episodic memory in semantic dementia.

Objective:

To unravel mutual and divergent functional alterations in Alzheimer’s disease and semantic dementia, we assessed functional connectivity between temporal lobe regions in Alzheimer’s disease (n = 16), semantic dementia (n = 23), and healthy controls (n = 17).

Methods:

In an exploratory study, we used a functional parcellation of the temporal cortex to extract time series from 66 regions for correlation analysis.

Results:

Apart from differing connections between Alzheimer’s disease and semantic dementia that yielded reduced functional connectivity, we identified a common pathway between the right anterior temporal lobe and the right orbitofrontal cortex in both dementia subtypes. This disconnectivity might be related to social knowledge deficits as part of semantic memory decline. However, such interpretations are preferably made in a holistic context of disease-specific semantic impairments and functional connectivity changes.

Conclusion:

Despite a major limitation owed to unbalanced databases between study groups, this study provides a preliminary picture of the brain’s functional disconnectivity in Alzheimer’s disease and semantic dementia. Future studies are needed to replicate findings of a common pathway with consistent diagnostic criteria and neuropsychological evaluation, balanced designs, and matched data MRI acquisition procedures.

中文翻译：

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语义性痴呆和阿尔茨海默病中颞叶和海马的功能连接改变。

 抽象的

 背景：

语义痴呆中的语义记忆障碍归因于前颞叶的萎缩和功能破坏。相比之下，阿尔茨海默病中发现的后内侧颞神经变性与情景记忆障碍有关。尽管语义性痴呆的情景记忆相对较少，但这两种痴呆亚型都有海马退化的情况。

 客观的：

为了揭示阿尔茨海默病和语义痴呆之间相互和不同的功能改变，我们评估了阿尔茨海默病 ( n = 16)、语义痴呆 ( n = 23) 和健康对照 ( n = 17) 颞叶区域之间的功能连接。

 方法：

在一项探索性研究中，我们使用颞叶皮层的功能分区从 66 个区域中提取时间序列进行相关分析。

 结果：

除了阿尔茨海默氏病和语义性痴呆之间的不同联系导致功能连接减少之外，我们还发现了两种痴呆亚型的右前颞叶和右眶额皮质之间的共同通路。这种脱节可能与社会知识缺陷有关，这是语义记忆衰退的一部分。然而，这种解释最好是在疾病特定的语义损伤和功能连接变化的整体背景下进行。

 结论：

尽管由于研究组之间的数据库不平衡而存在主要限制，但这项研究提供了阿尔茨海默氏病和语义痴呆症中大脑功能断开的初步图片。未来的研究需要通过一致的诊断标准和神经心理学评估、平衡的设计和匹配的数据 MRI 采集程序来复制共同通路的发现。