Working Memory Span in Normal Control, Mild Cognitive Impairment and Alzheimer's Disease

ABSTRACT

OBJECTIVE: The purposes of this study were to compare the working memory span between mild cognitive impairment (MCI) and Alzheimer's disease (AD) in the Korean elderly population and to evaluate the effectiveness of the working memory span tests. METHODS: 32 normal controls (NC), 26 patients with MCI and 28 AD patients at a mild stage were participated in this study. We used newly devised working memory span tests (Word span test and Dot matrix) according to the components of working memory ;central executive, phonological loop, and visuospatial sketchpad. And the results were compared with the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet (CERAD-K). To evaluate the effectiveness of the working memory tests and CERAD-K to screen MCI and AD, receiver operating characteristic curves were plotted. RESULTS: All subsets of the two working memory span tests showed significant decline in verbal and visuospatial working memory in AD. But there was no significant difference between NC and MCI. Compared to CERAD-K, the two working memory tests showed good effectiveness to discriminate AD. CONCLUSION: This study showed that working memory span tests could be effective diagnosing tools for detecting AD. But for the MCI, the working memory impairment was not prominent than episodic memory impairment. This is supposed to result from the various kinds of working memory components, especially the episodic buffer.