Motor-cognitive dual task performance : a neuro-cognitive approach investigating age-related differences based on the "Theory of Visual Attention"

Although an inherent part of everyday life, motor-cognitive dual-tasking - the ability to perform a cognitive and motor task simultaneously - still has many open questions. The mechanisms underlying these abilities are not well understood, and terms such as attention often make no clear distinction between various attentional sub-processes. This is especially true of the age-related decline in dual-tasking abilities, in which the visual task demands have been shown to become increasingly exigent. Two studies are presented in this dissertation. Study 1 introduced a novel paradigm to objectively measure motor-cognitive dual-task performance, whilst Study 2 used this new paradigm to investigate the impact of the aging process and of the cognitive load of a task on dual-tasking abilities. These studies combined a simple, continuous, and repetitive motor task with a whole report task based on the Theory of Visual Attention (TVA). This measures different parametric estimates of attentional performance, and shows how these were affected by a concurrent motor task. Each task was carried out separately as a single task, as well as simultaneously in a dual-task condition. Study 1 demonstrated that the visual processing rate and visual short-term memory (VSTM) storage capacity showed a dual-task-related decline in middle-aged adults. Study 2 indicated that older adults performing a simple motor task showed similar declines in performance as younger adults who carried out a more complex motor task. Taken together, the studies show that even a relatively simple motor task utilises a central attentional capacity, suggesting that motor-cognitive dual-tasking is conducted in a capacity sharing manner. Furthermore, the VSTM appears to be the constraining mechanism which underlies dual-tasking ability, and it is this central capacity which is negatively impacted in a qualitatively similar manner by both increased age in older adults, as well as by the task load in younger adults.