ABSTRACT
Over the past few decades, multiple cognitive deficits have been used to characterize persons with Alzheimer’s disease (AD). The most significant features among these deficits, including semantic impairments and progressive memory loss, have been widely examined (Brandt and Rich, 1995; Sebastian et al., 2001). Sebastian et al. (2001), for instance, examined the performance of 40 AD persons in the Brown-Peterson task and analyzed a pattern of errors, as compared with 55 elderly controls. The results showed that AD persons performed with lower scores in the three retention intervals than the healthy controls. But non-significant interaction was identified between group and interval. They argued for the similar rate of forgetfulness in the two groups and highlighted the problems in the central executive as well as in updating the working memory. Some earlier studies in psycholinguistics looked into the qualitative differences in prose discourse of persons with AD (see Abeysinghe et al., 1990; Lyons et al., 1994). Abeysinghe et al. (1990) was one of the pioneer reports on the nature of semantic memory impairment in AD persons. Three semantic tasks, including word association, definition, and associate rank ordering were implemented. Compared with healthy controls, the AD persons were more likely to give repetitious or unrelated responses. Additionally, the AD persons were unable to offer meaningful associates in the definition task and they were significantly impaired in identifying semantic associates of words. The results suggested that the AD persons were characterized by semantic memory deterioration and that semantic deficits were shown in the early stages of AD.
