Association of brain network efficiency with aging, depression, and cognition

Abstract

Objective: Newly developed techniques for understanding brain connectivity have emerged with the application of graph theory-based measures to neuroimaging modalities. However, the cognitive correlates of these measures, particularly in the context of clinical diagnoses like major depression, are still poorly understood. The purpose of this study was to compare four measures of network efficiency derived from novel techniques for understanding white matter connectivity on their associations with aging, depression, and cognition.

Methods: In a cross-sectional neuroimaging study, we recruited from the general community 43 healthy comparison subjects and 40 subjects with major depressive disorder who volunteered in response to advertisements. Brain network efficiency measures were generated from diffusion tensor imaging-derived structural connectivity matrices using the Brain Connectivity Toolbox. Information processing speed and decision making were assessed with the Trail Making Test and the Object Alternation task, respectively.

Results: All four network efficiency measures correlated negatively with age. In the depressed group, normalized global efficiency was negatively correlated with depression severity, whereas increasing global efficiency was associated with poorer performance on Object Alternation.

Conclusion: Brain network efficiency measures may represent different aspects of underlying network organization depending on the population and behaviors in question.

Keywords: Aging; cognition; connectivity; depression; network analysis.

Figure 1. Integrated global efficiency correlated with age

Correlation of age and integrated global efficiency. Age was negatively associated with integrated global efficiency in both subject groups (healthy comparison: dotted line; major depression: dashed line) and the total sample (solid line).

Figure 2. Local efficiency correlated with age

Correlation of age and local efficiency on an inferior view of the brain (A: Anterior, P: Posterior, L: Left, R: Right). a) Total sample, b) HC: healthy comparison group, c) MDD: major depression group. All nodes indicated in red, significantly associated nodes after false discovery rate correction are indicated in green. Each node represents a Freesurfer-defined brain region with the node placed at the coordinates of each brain region’s centroid.