Ageing and Dual Task Ability - Development of a new test for Alzheimer's Disease

Abstract

Patients with Alzheimer’s disease (AD) display a specific deficit in the ability to perform dual tasks requiring working memory. This executive function deficit has been shown in a number of different research paradigms to be absent from the normal ageing process, but the methodologies of these studies require bulky and expensive apparatus which make them unsuitable for use outside of dedicated laboratories. The current study aimed to develop a diagnostic test for AD which was compact and transportable. To be of value the test should not be sensitive to the effects of normal ageing on performance. Older and younger adults were assessed on dual tasking ability whilst performing a primary visuo-spatial tracking task and a task thought to load verbal working memory: immediate serial ordered digit recall. Difficulty in each of the tasks was equated across groups during an adaptive phase, and performance in single and dual task conditions was compared. Combined dual task performance did not differ significantly between the groups and younger adults’ performance in digit recall under dual task conditions was not significantly lower than in single task conditions. The results are consistent with the hypothesis that healthy ageing shows no evidence of a deficit in dual tasking ability present in AD. The paradigm tested may be suitable for future development as a sensitive and specific test for AD.