Ye, S.; Dave, A.; Salami, A.; Ziaei, M.

Functional dedifferentiation, a hallmark of brain aging particularly evident within the frontoparietal network (FPN), has been extensively investigated in the context of cognitive decline, yet its implications for late-life mental health remain poorly understood. Leveraging naturalistic fMRI combined with gradient mapping techniques, the present study investigated FPN functional dedifferentiation-quantified by functional dispersion of FPN in the multidimension gradient manifold-during real-life emotional experiences and its link to affective outcomes. Here, we estimated functional dispersion during naturalistic movie watching in both younger (N=72, 34 female, 19-36 yrs) and older (N=68, 36 female, 65-82 yrs) adult groups with 7T MRI scanner and assessed their emotion regulation difficulties, anxiety, and depression symptoms as indicators of mental health status. The results demonstrated that greater FPN dispersion (i.e., more dissimilar connectivity) was linked to increased depressive symptoms in older adults and highlighted emotion regulation difficulties as a full mediator of this relationship. Moreover, FPN dispersion could distinguish emotionally resilient from vulnerable older individuals. These findings suggest that functional dedifferentiation of the FPN during ecologically valid emotional context constitutes a promising neural signature of affective vulnerability in older adults. By bridging age-related functional dedifferentiation to real-world emotional scenario, this work underscores the translational value of naturalistic paradigms in geriatric psychiatry and identifies potential intervention targets aimed at enhancing FPN specificity to promote mental health in aging population.