Age differences of multivariate network expressions during task-switching and their associations with behavior.

The effect of aging on functional network activation associated with task-switching was examined in 24 young (age=25.2±2.73 years) and 23 older adults (age=65.2±2.65 years) using functional magnetic resonance imaging (fMRI). The study goals were to (1) identify a network shared by both young and older adults, (2) identify additional networks in each age group, and (3) examine the relationship between the networks identified and behavioral performance in task-switching. Ordinal trend covariance analysis was used to identify the networks, which takes advantage of increasing activation with greater task demand to isolate the network of regions recruited by task-switching. Two task-related networks were found: a shared network that was strongly expressed by both young and older adults and a second network identified in the young data that was residualized from the shared network. Both networks consisted of regions associated with task-switching in previous studies including the middle frontal gyrus, the precentral gyrus, the anterior cingulate, and the superior parietal lobule. Not only was pattern expression of the shared network associated with reaction time in both age groups, the difference in the pattern expression across task conditions (task-switch minus single-task) was also correlated with the difference in RT across task conditions. On the contrary, expression of the young-residual network showed a large age effect such that older adults do not increase expression of the network with greater task demand as young adults do and correlation between expression and accuracy was significant only for young adults. Thus, while a network related to RT is preserved in older adults, a different network related to accuracy is disrupted.