Assessment of verbal and visuospatial working memory in mild cognitive impairment and Alzheimer's dementia

In addition to episodic memory impairment, working memory may also be compromised in mild cognitive impairment (MCI) or Alzheimer's dementia (AD), but standard verbal and visuospatial span tasks do not always detect impairments. Objective: To examine whether more complex verbal and visuospatial working memory tasks result in more reliable impairment detection. Methods: The Digit Span (forward, backward and sequencing), Spatial Span (forward and backward) and Spatial Addition test from the Wechsler batteries were administered to MCI and AD patients and performance compared to healthy older adult controls. Results: Results showed that both the MCI and AD patients had impaired performance on the Spatial Addition test. Both groups also had impaired performance on all three Digit Span conditions, but no differences were found between forward and backward conditions in any of the groups. The sequencing condition differed from the backward condition only in the AD group. Spatial Span performance was impaired in AD group patients but not in MCI patients. Conclusion: Working memory deficits are evident in MCI and AD even on standard neuropsychological tests. However, available tests may not detect subtle impairments, especially in MCI. Novel paradigms tapping the episodic buffer component of working memory may be useful in the assessment of working memory deficits, but such instruments are not yet available for clinical assessment.

除情景记忆（episodic memory）受损外，轻度认知障碍（MCI）或阿尔茨海默病痴呆（AD）患者的工作记忆也可能受损，但常规言语与视空间广度任务往往难以检出此类损伤。研究目的：探究更复杂的言语与视空间工作记忆任务是否能更可靠地检出工作记忆损伤。研究方法：对MCI患者、AD患者施测韦氏成套测验中的数字广度测验（顺向、逆向与序列版）、空间广度测验（顺向与逆向版）以及空间加法测验，并将其表现与健康老年对照人群进行比较。研究结果：结果显示，MCI与AD患者在空间加法测验中均表现出受损。两组在三项数字广度测验条件下的表现均存在损伤，但所有组别中顺向与逆向条件间均未发现显著差异。仅在AD组中，序列版数字广度测验与逆向版测验的表现存在差异。AD患者的空间广度测验表现受损，而MCI患者则未出现此现象。研究结论：即便采用常规神经心理学测验，MCI与AD患者的工作记忆缺陷仍可被明确检出。但现有测验可能无法识别细微的损伤，尤其在MCI患者中。针对工作记忆情景缓冲器成分的新型范式或许有助于评估工作记忆缺陷，但此类工具目前尚未应用于临床评估。