Resting-State Functional Connectivity in Late-Life Depression: Higher Global Connectivity and More Long Distance Connections

TL;DR

This study reveals that late-life depression is associated with increased resting-state functional connectivity, especially in long-distance brain connections, without altering overall network topology.

Contribution

It provides new insights into the specific connectivity alterations in late-life depression, highlighting increased global and long-distance connections without changing network organization.

Findings

Higher FC in LLD compared to controls

Increased average Euclidean distance between connected regions in LLD

More diffuse connectivity of the right caudate nucleus in LLD

Abstract

Functional magnetic resonance imaging recordings in the resting-state (RS) from the human brain are characterized by spontaneous low-frequency fluctuations in the blood oxygenation level dependent signal that reveal functional connectivity (FC) via their spatial synchronicity. This RS study applied network analysis to compare FC between late-life depression (LLD) patients and control subjects. Raw cross-correlation matrices (CM) for LLD were characterized by higher FC. We analyzed the small-world (SW) and modular organization of these networks consisting of 110 nodes each as well as the connectivity patterns of individual nodes of the basal ganglia. Topological network measures showed no significant differences between groups. The composition of top hubs was similar between LLD and control subjects, however in the LLD group posterior medial-parietal regions were more highly connected compared to controls. In LLD, a number of brain regions showed connections with more distant neighbors leading to an increase of the average Euclidean distance between connected regions compared to controls. In addition, right caudate nucleus connectivity was more diffuse in LLD. In summary, LLD was associated with overall increased FC strength and changes in the average distance between connected nodes, but did not lead to global changes in SW or modular organization.