ABSTRACT

In Alzheimer’s dementia (AD), greater declines in semantic fluency (SF) relative to letter fluency (LF) have been assumed to reflect semantic disintegration. However, the same pattern is observed in typical aging and neurodegenerative disorders besides AD. We examined this assumption by comparing different aspects of SF and LF performance in older adults with and without dementia, and identifying which verbal fluency measures most clearly distinguish AD from typical aging. Verbal fluency data were compared from 109 individuals with AD and 66 typically aging adults. Correct items, clusters, and errors were analyzed using both raw counts and proportions. Regression analyses examined Task-by-Group interactions and the impact of demographic variables on verbal fluency measures. ROC analyses examined the sensitivity and specificity of the different outcome measures. In regressions, interactions were found for raw but not proportional data, indicating that different group patterns were driven largely by the number of correct items produced. Similarly, in ROC analyses, raw SF totals showed stronger discriminability between groups than either raw discrepancy scores (SF–LF) or discrepancy ratios (SF/LF). Age and cognitive status (MMSE) were the strongest individual predictors of performance. Findings suggest that AD entails quantitative declines in verbal fluency, but qualitatively similar patterns of performance relative to typically aging adults. Thus, SF declines in AD seem to be at least partially attributable to an exaggeration of the underlying mechanisms common to typical aging, and do not necessarily implicate semantic disintegration.

摘要

在阿尔茨海默氏痴呆症 (AD) 中，语义流畅性 (SF) 相对于字母流畅性 (LF) 的下降幅度更大，被认为反映了语义瓦解。然而，除了 AD 之外，在典型的衰老和神经退行性疾病中也观察到相同的模式。我们通过比较患有和不患有痴呆症的老年人的 SF 和 LF 表现的不同方面来检验这一假设，并确定哪些言语流畅性指标最能清楚地区分 AD 和典型衰老。对 109 名 AD 患者和 66 名典型老年人的言语流利度数据进行了比较。使用原始计数和比例来分析正确的项目、聚类和错误。回归分析检查了任务组交互以及人口变量对言语流畅性测量的影响。ROC 分析检查了不同结果指标的敏感性和特异性。在回归中，发现了原始数据而非比例数据的交互作用，这表明不同的组模式很大程度上是由产生的正确项目的数量驱动的。同样，在 ROC 分析中，原始 SF 总数显示出比原始差异分数 (SF-LF) 或差异比率 (SF/LF) 更强的组间可区分性。年龄和认知状态（MMSE）是最强的个人表现预测因素。研究结果表明，AD 会导致言语流畅性在数量上下降，但与典型的老年人相比，其表现模式在质量上相似。因此，AD 中 SF 的下降似乎至少部分归因于对典型衰老常见的潜在机制的夸大，并且并不一定意味着语义瓦解。