前驅期阿茲海默病個體語意記憶缺損之型態與預測認知退化能力

Abstract

針對阿茲海默病之神經病理研究指出語意記憶缺損在病程演進中可能早於事件記憶，近期許多研究於失憶型輕度認知缺損患者中發現語意記憶缺損；然而，研究對於語意記憶缺損對於日後轉變為阿茲海默型失智症之預測能力看法不一，此外，目前尚無研究探討主觀記憶缺損個體之語意記憶。本研究目標為探討失憶型輕度認知缺損患者語意記憶缺損之不同面向並提供這些面向對於轉變為阿茲海默型失智症之預測效果，另外，本研究亦探討主觀記憶缺損個體記憶中之語意面向。主觀記憶缺損個體及單一領域失憶型輕度認知缺損患者在費力、策略性語意記憶提取歷程明顯受損，而多重領域失憶型輕度認知缺損患者在費力及自動性語意記憶提取歷程皆受損；由單一領域失憶型輕度認知缺損轉變為阿茲海默型失智症受到費力性語意記憶提取缺損所預測，相反的，由多重領域失憶型輕度認知缺損轉變為阿茲海默型失智症受到自動性語意記憶提取缺損所預測。這些發現顯示失憶型輕度認知缺損患者及具有主觀記憶缺損個體在語意記憶缺損上呈現特有型態，此類缺損型態具有預測失憶型輕度認知缺損患者後續認知退化之效果。

Neuropathological evidence suggests that semantic memory deterioration can occur earlier than episodic memory in the disease progression of Alzheimer’s disease (AD). Increasing evidence has suggested marked semantic memory impairment in patients with amnestic mild cognitive impairment (aMCI-sd). However, the predicative power of semantic memory on conversion from aMCI to dementia of the Alzheimer’s type (DAT) has remained inconsistent. In addition, no studies have directly investigated semantic memory among individuals with subjective memory decline (SMD). This study aimed to investigate various aspects of semantic memory decline among aMCI patients, to evaluate the predictive values of these aspects of semantic memory on conversion to DAT, and to examine the semantic aspect of memory among SMD individuals. Individuals with SMD and patients with aMCI-single domain (aMCI-sd) suffered from disproportionately impaired performance on effortful and strategic retrieval of semantic memory, whereas those with aMCI-multiple domain (aMCI-md) suffered from deficits in both effortful and automatic retrieval of semantic memory. The conversion from aMCI-sd to DAT was predicted by poor performance in effortful retrieval of semantic memory. In contrast, conversion from aMCI-md to DAT was predicted by poor performance on automatic retrieval. These findings suggest distinctive patterns and predictive values of semantic memory deterioration among individuals in the earliest stages of AD.