Working memory deficits in Alzheimer's disease

The phonological loop and central executive components of working memory were examined in patients with Alzheimer's disease (AD patients) and elderly controls. Patients with Alzheimer's disease showed reduced verbal spans, with smaller phonological similarity and word length effects. They also showed a decreased performance in tasks examining processing speed and articulation rate. However, phonological analysis was normal. With regard to the central executive, AD patients showed deficits in an alphabetical span task in which subjects were asked to recall a random series of words in their alphabetical order, while they performed normally on a dual task in which they had to perform simultaneously a digit repetition and a visuomotor task. These results suggests that Alzheimer's disease may affect several components of working memory but all aspects of the central executive mechanism are not necessarily affected.