Age-related changes in brain activation underlying single- and dual-task performance: visuomanual drawing and mental arithmetic.

Depending on task combination, dual-tasking can either be performed successfully or can lead to performance decrements in one or both tasks. Interference is believed to be caused by limitations in central processing, i.e. structural interference between the neural activation patterns associated with each task. In the present study, single- and dual-task effects were addressed in the context of aging. Increasing evidence from research on motor and cognitive tasks has shown that aging is associated with an expansion of brain activation and an increased BOLD-signal. This may result in increased structural interference and higher dual-task interference in older adults. Functional magnetic resonance imaging was used to measure the BOLD-response in 20 old and 20 young healthy adults while performing tasks separately, or combined. Single tasks consisted of mental arithmetic cued by auditory tones, and a visuomotor task, drawing a circular shape with spatiotemporal constraints. Age-related brain activation increases were only apparent during performance of the visuomotor task. Elderly showed higher BOLD-responses in a frontoparietal network, pointing to an increased reliance on sensory feedback processing. However, no increased structural interference was found for the elderly during performance of the dual-task. Region of interest analysis involving a functional cluster within the (pre-) supplementary motor area, active during performance of both single-tasks, revealed that both groups were able to upregulate their brain activity for dual-as compared to single-task performance. We assume that this allowed both groups to maintain performance under dual-task conditions, leading to minimal dual-task interference.