Temporal dynamics of intrinsic brain activity in older women with subclinical depression.

Subclinical depression is common in older adults, especially in females, and may correlate with a higher likelihood of health events and poor prognosis. However, the underlying neurobiology remains unclear. This study, employing resting-state functional magnetic resonance imaging (rs-fMRI), identified alterations in temporal dynamics of intrinsic brain activity in older women with subthreshold depression (OWSD) and their potential relationships to depressive symptoms. The sliding window approach was applied to evaluate the temporal variations of the rs-fMRI indices, including the amplitude of low-frequency fluctuation (ALFF), the fractional amplitude of low-frequency fluctuation (fALFF), regional homogeneity (ReHo), and degree centrality (DC) in 50 OWSD and 52 healthy older women controls (HOWC). We then calculated the dynamic voxel-wise concordance index of the rs-fMRI indices. The correlational analyses were used to assess the correlations between the dynamic indices and depressive symptoms. We found that OWSD showed a significant increase in dynamic ALFF (dALFF) in the left dorsolateral prefrontal cortex (DLPFC) relative to HOWC. With respect to regional brain function integration, OWSD showed a significantly lower dynamic voxel-wise concordance index in the right parietal lobe, mainly including the precuneus and superior parietal lobule extending to the postcentral gyrus. The regional dALFF and dynamic concordance index alterations were correlated with depressive symptoms. In conclusion, OWSD showed depression-correlated alterations in temporal variability of intrinsic brain activity, along with regional deficits in brain function integration. The findings reinforce our understanding of subthreshold depression psychopathology in older women.