Brain functional characterization of response-code conflict in dual-tasking and its modulation by age
Crosstalk between conflicting response codes contributes to interference in dual-tasking, an effect exacerbated in advanced age. Here, we investigated (1) brain activity correlates of such response-code conflicts, (2) activity modulations by individual dual-task performance and related cognitive abilities, (3) task-modulated connectivity within the task network, and (4)age-related differences in all these aspects. Young and older adults underwent fMRI while responding to the pitch of tones through spatially mapped speeded button presses with one or two hands concurrently. Using opposing stimulus-response mappings between hands, we induced conflict between simultaneously activated response codes. These response-code conflicts elicited activation in key regions of the multiple-demand network. Older adults showed non-compensatory hyperactivity in left superior frontal gyrus, and higher left intraparietal sulcus activity associated with lower attentional performance. While motor and parietal areas of the conflict-related network were modulated by attentional and task-switching abilities, efficient conflict resolution in dual-tasking was linked to suppressing visual cortex activity. Finally, connectivity between premotor or parietal seed regions and the conflict-sensitive network was neither conflict-specific nor age-sensitive. Overall, resolving dual-task response-code conflict recruited substantial parts of the multiple-demand network, whose activity and coupling, however, were only little affected by individual differences in task performance or age.