AGING IMPACTS ON INTER-SUBJECT SIMILARITY OF FUNCTIONAL CONNECTIVITY STRUCTURE DURING EXECUTIVE-FUNCTION TASK

The similarity of the architecture of functional connectivity (FC) in resting state indicates individual variability and can be influenced by aging. The aim of this study is, using functional MRI (fMRI), to investigate the impact of aging on resting state FC (rest-FC) and FC during executive-function task (task-FC). We acquired fMRI data during resting state and Stroop task in 29 older and 22 younger adults. In the Stroop task, participants name ink color and responses are slower when the word’s meaning and ink color are incongruent than when they are congruent. We identified 27 brain regions related to Stroop task processing using a hierarchical Bayesian approach. Then, rest-FC and task-FC were computed as the temporal correlation between the signals of each pair of regions. The task-FC was calculated during the time series of fMRI signals in task blocks. Inter-subject similarity was quantified by computing within-condition correlations across participants. The difference in response time between incongruent and congruent conditions (ΔRT) was significantly greater in older adults than in younger adults. The connectivity strength of task-FC between the left paracingulate gyrus and several regions including the middle frontal gyrus was positively correlated with ΔRT in older adults but not in younger adults. Rest-FC showed high similarity across all subjects and was comparable between groups (Figure). In contrast, similarity of task-FC in older adults was lower than that within younger adults. These results indicate that similarity of rest-FC is preserved in aging, whereas functional connectivity similarity is reduced during executive control.