MEMORY SPAN PROCEDURES IN ALZHEIMERS-DISEASE

In a working memory framework, the forward memory span involves a subs idiary system that maintains information, and the backward span relies on a central executive system (CES) that allocates processing resourc es. The authors hypothesized that a measure of the CES derived from th e backward span would distinguish Alzheimer's disease (AD) patients (n = 49) from elderly controls without dementia (n = 49), vary as a func tion of disease severity, and underlie other cognitive disturbances. M emory span procedures were Digit Span Forward and Backward and Visual Memory Span Forward and Backward. Derived CES measures discriminated b etween groups, predicted dementia severity, and predicted performance on some of the cognitive tasks examined. However, working memory subsi diary systems also appeared to be affected in AD, and some cognitive d eficits in AD were independent of working memory disturbances. The vis ual memory span backward was the best predictor of group and of dement ia severity.