Altered static and dynamic functional network connectivity in individuals with subthreshold depression: a large-scale resting-state fMRI study

Jul 23, 2024European archives of psychiatry and clinical neuroscience

Changes in steady and changing brain network connections in people with mild depression symptoms

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Abstract

Individuals with subthreshold depression show decreased functional network connectivity strength compared to healthy controls.

Subthreshold depression is associated with reduced static functional network connectivity strength in multiple brain networks, including the default mode network and executive control network.
Dynamic functional network connectivity analysis identified four recurring patterns in individuals with subthreshold depression.
StD individuals exhibited increased time spent in a weakly connected state, which relates to self-focused thinking.
There was decreased dynamic functional network connectivity strength between the default mode network and dorsal attentional network in individuals with subthreshold depression.
Correlations were found between static functional network connectivity strength and temporal properties with depression severity as measured by the HAMD-17 score.

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Dynamic functional network connectivity (dFNC) is an expansion of static FNC (sFNC) that reflects connectivity variations among brain networks. This study aimed to investigate changes in sFNC and dFNC strength and temporal properties in individuals with subthreshold depression (StD). Forty-two individuals with subthreshold depression and 38 healthy controls (HCs) were included in this study. Group independent component analysis (GICA) was used to determine target resting-state networks, namely, executive control network (ECN), default mode network (DMN), sensorimotor network (SMN) and dorsal attentional network (DAN). Sliding window and k-means clustering analyses were used to identify dFNC patterns and temporal properties in each subject. We compared sFNC and dFNC differences between the StD and HCs groups. Relationships between changes in FNC strength, temporal properties, and neurophysiological score were evaluated by Spearman's correlation analysis. The sFNC analysis revealed decreased FNC strength in StD individuals, including the DMN-CEN, DMN-SMN, SMN-CEN, and SMN-DAN. In the dFNC analysis, 4 reoccurring FNC patterns were identified. Compared to HCs, individuals with StD had increased mean dwell time and fraction time in a weakly connected state (state 4), which is associated with self-focused thinking status. In addition, the StD group demonstrated decreased dFNC strength between the DMN-DAN in state 2. sFNC strength (DMN-ECN) and temporal properties were correlated with HAMD-17 score in StD individuals (all p < 0.01). Our study provides new evidence on aberrant time-varying brain activity and large-scale network interaction disruptions in StD individuals, which may provide novel insight to better understand the underlying neuropathological mechanisms.

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Altered static and dynamic functional network connectivity in individuals with subthreshold depression: a large-scale resting-state fMRI study

Abstract

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