Cherry Barbara J, Buckwalter J Galen, Henderson Victor W
Department of Neurology, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
Neuropsychologia. 2002;40(7):846-52. doi: 10.1016/s0028-3932(01)00173-7.
It is suggested that Alzheimer's disease (AD) patients are able to recall more items on the digit span task than on immediate free recall from a supraspan word list. Two experiments were undertaken to verify this assertion and to understand the basis of the putative span/supraspan discrepancy. The first experiment, involving 35 mildly or moderately demented AD patients, confirmed that digit span significantly exceeded immediate recall from a 10-item supraspan word list. Although digit span also exceeded supraspan recall in 38 elderly non-demented control subjects, the discrepancy was significantly greater within the AD group. In a second experiment, 19 AD cases and 20 controls were assessed with a word span task that used nouns matched by frequency and word length to nouns on the supraspan task. The magnitude of the span/supraspan discrepancy was reduced, indicating that part of the initial discrepancy was due to differences in stimulus items (digits versus common nouns). As before, AD subjects recalled more words on the span task than the supraspan task. However, in striking contrast, NC subjects recalled more words on the supraspan task, further indicating that AD patients are particularly impaired on supraspan recall. Using combined data from 106 subjects in both experiments, digit span performance correlated significantly with supraspan recall for NC but not AD subjects. Moreover, within the AD group the magnitude of the discrepancy was inversely related to a working memory measure derived from the backward digit span. The magnitude of the span/supraspan discrepancy correctly classified 88% of patients with mild dementia and 74% of controls. Results indicate that AD patients are specifically vulnerable to information overload inherent in the supraspan task, a view consistent with the perspective that AD is characterized by prominent disturbances in working memory.
有研究表明，阿尔茨海默病（AD）患者在数字广度任务中能够回忆起的项目比从超广度单词列表中进行即时自由回忆时更多。为此进行了两项实验来验证这一论断，并了解假定的广度/超广度差异的基础。第一项实验涉及35名轻度或中度痴呆的AD患者，证实数字广度显著超过了从10个项目的超广度单词列表中的即时回忆。虽然在38名老年非痴呆对照受试者中数字广度也超过了超广度回忆，但AD组内的差异明显更大。在第二项实验中，对19名AD患者和20名对照者进行了一项单词广度任务评估，该任务使用的名词在频率和单词长度上与超广度任务中的名词相匹配。广度/超广度差异的幅度有所减小，这表明最初差异的一部分是由于刺激项目（数字与普通名词）的不同。和之前一样，AD受试者在广度任务中回忆的单词比超广度任务中更多。然而，与之形成鲜明对比的是，非痴呆（NC）受试者在超广度任务中回忆的单词更多，这进一步表明AD患者在超广度回忆方面特别受损。使用两项实验中106名受试者的综合数据，数字广度表现与NC受试者的超广度回忆显著相关，但与AD受试者无关。此外，在AD组内，差异的幅度与从倒背数字广度得出的工作记忆测量值呈负相关。广度/超广度差异的幅度正确地将88%的轻度痴呆患者和74%的对照者区分开来。结果表明，AD患者特别容易受到超广度任务中固有的信息过载的影响，这一观点与AD以工作记忆显著障碍为特征的观点一致。
