An investigation of divided attention impairments in Huntington’s disease and ageing

Divided attention, the ability to attend and respond simultaneously to two or more stimuli or tasks, has been typically investigated using dual task paradigms. Dual task paradigms have been extensively used to examine attentional demands in healthy people, including various age and patient groups. The effect of ageing on dual task performance is well-documented; however, dual task research on Huntington’s disease (HD) is very limited, despite evidence suggesting poor dual task performance in this disease. The overarching aim of this thesis was to investigate dual task performance in HD, and in younger (18-30 years) and older (> 60 years) healthy adults. To achieve this aim, we used a battery of dual tasks that varied in their input (e.g., visual, auditory) and output (e.g., motor, verbal) modalities. Each task was examined under two difficulty levels: easy and hard. Tasks were chosen based on past dual task research in HD and ageing, and divided attention theories (e.g., resource allocation theories). Overall, our results showed that HD participants were slower and less accurate across all task conditions compared with controls. Similarly, older adults were slower and less accurate compared with younger adults. With a few exceptions, differences reached statistical significance either in terms of speed or accuracy within each set of tasks. Our findings suggest differential effects of dual task performance in people with HD compared to healthy individuals, and between younger and older adults. Findings also highlight the importance of taking into account different measures of performance (e.g., speed, accuracy, dual task costs, etc.) since relationships between groups may differ across measures. In regards to the effect of difficulty, overall, dual tasks were performed slower and less accurately than single tasks, and harder levels were performed slower and less accurately than easier levels. A key outcome of our research is that HD participants and older adults may adopt differential behavioural strategies depending on the type of concurrent task, compared with controls and younger adults, respectively. Further investigation of dual tasking in HD and ageing, in conjunction with other tasks, will contribute to better understanding of attentional impairments that manifest with disease progression and older age. Consequently, this knowledge will assist with the development of adaptive strategies or treatments to improve functioning in people with HD and in the elderly.