Task-specific ISS reduction and network balance during Stroop task performance in older adults

Declines in the cognitive inhibition that comes with aging impacts daily life and independence. It is still debated whether overactivation during cognitive inhibition tasks in older adults is due to compensation or neural noise. To address this question, we examined age-related changes in inter-subject similarity (ISS) of functional connectivity from task-based and resting-state fMRI. Using Bayesian hierarchical modeling, we identified 27 Stroop task-related regions of interest and found that ISS in these regions was significantly reduced in older adults during task performance. Furthermore, aging is associated with a loss of consistent functional connectivity patterns in frontal regions, accompanied by the emergence of a convergent compensatory mechanism within visual attention regions. Principal component analysis of individual activation deviations from the group-mean pattern showed that task performance in older adults cannot be explained by overall task-related brain activation, but rather by a specific spatial component involving suppression of the default mode network and increased activity in visual attention regions. These findings indicate that task-related brain overactivation in older adults is not due to uniform noise or uniform compensation, but rather a spatially specific pattern of functional reorganization.