Shared and Specific Intrinsic Functional Connectivity Patterns in Unmedicated Bipolar Disorder and Major Depressive Disorder

Abstract

Identifying brain differences and similarities between bipolar disorder (BD) and major depressive disorder (MDD) is necessary for increasing our understanding of the pathophysiology and for developing more effective treatments. However, the features of whole-brain intrinsic functional connectivity underlying BD and MDD have not been directly compared. We collected resting-state fMRI data from 48 BD patients, 48 MDD patients, and 51 healthy subjects. We constructed voxel-wise whole-brain functional networks and computed regional functional connectivity strength (FCS) using graph-theory and further divided the regional FCS into long-range FCS (lFCS) and short-range FCS (sFCS). Relative to the controls, both the BD and MDD patients showed decreased sFCS in the bilateral precuneus. In addition, the BD patients showed increased and the MDD patients showed decreased lFCS and sFCS in the bilateral cerebellum. The BD patients also showed increased lFCS in the right middle temporal gyrus and increased sFCS in the bilateral thalamus compared to either the MDD patients or the controls. These findings suggest that BD and MDD may have some shared as well as a greater number of specific impairments in their functional connectivity patterns, providing new evidence for the pathophysiology of BD and MDD at the large-scale whole brain connectivity level.

Aberrant brain network topology in fronto‐limbic circuitry differentiates euthymic bipolar disorder from recurrent major depressive disorder

“…Functional connectivity alterations in the temporal lobes between BD and MDD have been consistently reported by prior studies (He et al, 2016;Rive et al, 2016;Wang, Wang, Jia, Zhong, Niu et al, 2017;. Interestingly, previous structural MRI studies have reported decreased cortical thickness in temporal as well as frontal areas including the ACC in individuals with BD (Hanford, Nazarov, Hall, & Sassi, 2016).…”

“…Interestingly, previous structural MRI studies have reported decreased cortical thickness in temporal as well as frontal areas including the ACC in individuals with BD (Hanford, Nazarov, Hall, & Sassi, ). Wang, Wang, Jia, Zhong, Niu et al () examined a patient sample of currently depressed BD and MDD and proposed that their findings of an increased long‐range functional connectivity strength in the middle temporal gyrus in BD may display a compensatory mechanism to account for the impairments in gray matter structure (Wang, Wang, Jia, Zhong, Niu et al, ). We second this proposition and further hypothesize that the pattern we found in the frontal and temporal regions of our BD sample (high measures of centrality alongside low PL) may indicate structural deficits in these areas which the brain tries to compensate through a denser, more integrated functional organization.…”

“…Recently, graph analysis using graph theoretical measures has been applied to explore brain network properties in individuals with psychiatric disorders (Bassett & Bullmore, ; He et al, ; Manelis et al, ; Wang, Wang, Jia, Zhong, Niu et al, ; Wang, Wang, Jia, Zhong, Zhong et al, ). Using graph analysis, the brain is modulated as a network of nodes (most commonly a priori defined regions) that are connected by edges resembling functional connections between these regions (Bassett & Bullmore, ).…”

Cognitive function following a major depressive episode: a systematic review and meta-analysis

“…These results are consistent with cumulative research showing similar clinical characteristics, brain functioning and predictors of remission for unipolar and bipolar depression. [54][55][56] Nevertheless, high quality replication studies in patients remitted from bipolar depression, specifically focusing on cognition would be beneficial. Current medication might have also influenced the results.…”

Frequency-Specific Resting Connectome in Bipolar Disorder: An MEG Study

“…Simultaneously, graph theory analysis has been applied to explore brain network connectivity in psychiatric patients (21)(22)(23)(24)(25). Graphs are defined as sets of nodes and edges that represent system components and their mutual relationships (26).…”