The Memory Deficits in Alzheimer-Type Dementia: A Review

Abstract

This review is an account of recent experimental studies of memory deficits at the early stages of Alzheimer-type dementia, evaluating these studies in relation to current theories of memory functioning in humans. Whilst memory deficits are found to be widespread, some aspects are more resilient to impairment than others. For example, the processes associated with articulatory rehearsal in working memory are unimpaired despite a reduction in performance on most tests of primary memory. The “implicit” aspects of secondary memory appear to remain unimpaired, in contrast to a marked decline in “explicit” or “episodic” memory. In addition, there is evidence that the rate of forgetting from secondary memory is normal. Some aspects of episodic and semantic memory are found to be impaired as a consequence of a decline in the efficient organisation and processing of verbal material at encoding or retrieval. It is concluded that the deficits share particular features found in organic amnesia, but with additional deficits which relate to impairments in other domains of functioning.