Altered brain network modules induce helplessness in major depressive disorder

Abstract

Objective The abnormal brain functional connectivity (FC) has been assumed to be a pathophysiological aspect of major depressive disorder (MDD). However, it is poorly understood, regarding the underlying patterns of global FC network and their relationships with the clinical characteristics of MDD. Methods Resting-state functional magnetic resonance imaging data were acquired from 16 first episode, medication-naïve MDD patients and 16 healthy control subjects. The global FC network was constructed using 90 brain regions. The global topological patterns, e.g., small-worldness and modularity, and their relationships with depressive characteristics were investigated. Furthermore, the participant coefficient and module degree of MDD patients were measured to reflect the regional roles in module network, and the impairment of FC was examined by network based statistic. Results Small-world property was not altered in MDD. However, MDD patients exhibited 5 atypically reorganized modules compared to the controls. A positive relationship was also found among MDD patients between the intra-module I and helplessness factor evaluated via the Hamilton Depression Scale. Specifically, eight regions exhibited the abnormal participant coefficient or module degree, e.g., left superior orbital frontal cortex and right amygdala. The decreased FC was identified among the sub-network of 24 brain regions, e.g., frontal cortex, supplementary motor area, amygdala, thalamus, and hippocampus. Limitation The limited size of MDD samples precluded meaningful study of distinct clinical characteristics in relation to aberrant FC. Conclusions The results revealed altered patterns of brain module network at the global level in MDD patients, which might contribute to the feelings of helplessness.

Age-Related Reorganizational Changes in Modularity and Functional Connectivity of Human Brain Networks

“…Several studies have reported that the modular organization could be affected under neuropsychological conditions and disorders, including depression (Peng et al, 2014), Schizophrenia (Alexander-Bloch et al, 2014), epilepsy (Xu et al, 2013), and age-related neurodegenerative diseases such as Parkinson's disease (Gottlich et al, 2013) and AD (Kikuchi et al, 2013). One study also observed age-related alterations in the modular organization using cortical thickness analysis (Chen et al, 2011).…”

“…Modules consist of densely intraconnected brain regions that are sparsely inter-connected with regions in other modules (Newman and Girvan, 2004). Modular organization may represent stable subcomponents of the brain that facilitate the construction of a complex system from simple building blocks, and can be theoretically linked to network development (Alexander-Bloch et al, 2010), which has provided insights into abnormal brain development, neuropsychological conditions (Alexander-Bloch et al, 2014;Peng et al, 2014;Xu et al, 2013), and age-related neurodegenerative diseases (Gottlich et al, 2013;Kikuchi et al, 2013). Therefore, in this study, we hypothesize that the brain functional modular structure can be affected by aging and that age-related changes in modularity can be revealed by graph theory analysis.…”

Altered resting-state functional connectivity in emotion-processing brain regions in adults who were born very preterm

“…In view of previous observations that amygdalar connectivity is reduced in individuals with mood disorders, and that this dysconnectivity relates to clinical symptoms and emotion-processing performance (e.g. Peng et al 2014), we hypothesized that VPT individuals would exhibit: (1) reduced rs-fc between the amygdala and key nodes of an emotion-processing network (Leppänen & Nelson, 2009); (2) lower accuracy and longer reaction times than controls at recognizing emotions at lower intensity levels; and (3) functional integrity of the amygdala connectivity network would be related to performance on the ERT. Post-hoc exploratory analyses investigating associations between rs-fc, emotion recognition, full-scale IQ and perinatal variables were additionally conducted.…”

Abnormal dynamic functional connectivity of amygdalar subregions in untreated patients with first-episode major depressive disorder

“…For example, decreased FC has been identified in the amygdala, frontal cortex, supplementary motor area (SMA), thalamus and hippocampus in medication-naive adults with first-episode MDD. 15 Impaired amygdala FC has also been found in adults with late-life depression 16 and adolescents with MDD. 9 However, increasing evidence suggests that the amygdala is a complex of structurally and functionally heterogeneous nuclei rather than a single homogeneous structure.…”