Working memory and vigilance: evidence from normal aging and Alzheimer's disease.

Both single unit recording and neuroradiological studies suggest that frontal and executive processes are necessary for visual maintenance rehearsal. This observation is linked to the classic vigilance literature by the proposal that vigilance decrement is found when the subject is required to maintain a representation over a brief delay. Vigilance performance was therefore studied in a sample of elderly subjects who were tested over a 40-min period involving perceptual or memory-based tasks which were matched for initial level of performance. There was a significant interaction between task and delay, with only the memory-based task showing decrement. A second study used the same two tasks to investigate vigilance performance in patients suffering from probable Alzheimer's Disease. Over a 15-min delay period, an equivalent interaction effect occurred, again indicating substantially greater decrement for the memory-based task. The results are interpreted as consistent with a role for the executive processes of working memory in both visual rehearsal and vigilance performance. Copyright 1999 Academic Press.