Altered functional activity in bipolar disorder: A comprehensive review from a large‐scale network perspective

Abstract

Background Growing literature continues to identify brain regions that are functionally altered in bipolar disorder. However, precise functional network correlates of bipolar disorder have yet to be determined due to inconsistent results. The overview of neurological alterations from a large‐scale network perspective may provide more comprehensive results and elucidate the neuropathology of bipolar disorder. Here, we critically review recent neuroimaging research on bipolar disorder using a network‐based approach. Methods A systematic search was conducted on studies published from 2009 through 2019 in PubMed and Google Scholar. Articles that utilized functional magnetic resonance imaging technique to examine altered functional activity of major regions belonging to a large‐scale brain network in bipolar disorder were selected. Results A total of 49 studies were reviewed. Within‐network hypoconnectivity was reported in bipolar disorder at rest among the default mode, salience, and central executive networks. In contrast, when performing a cognitive task, hyperconnectivity among the central executive network was found. Internetwork functional connectivity in the brain of bipolar disorder was greater between the salience and default mode networks, while reduced between the salience and central executive networks at rest, compared to control. Conclusion This systematic review suggests disruption in the functional activity of large‐scale brain networks at rest as well as during a task stimuli in bipolar disorder. Disrupted intra‐ and internetwork functional connectivity that are also associated with clinical symptoms suggest altered functional connectivity of and between large‐scale networks plays an important role in the pathophysiology of bipolar disorder.

Segregation, integration and balance in resting‐state brain functional networks associated with bipolar disorder symptoms

“…Diverse BD symptoms involve widespread activation across brain regions, and a network‐based investigation may more comprehensively contribute to understanding the pathology of this disorder (Yoon et al, 2021 ). Neuroimaging studies have implicated dysfunction in emotion regulation networks in BD (Strakowski et al, 2012 ) that has mainly been incorporated into two theories related to brain imbalance.…”

Normative model detects abnormal functional connectivity in psychiatric disorders

“…It has been previously suggested that basal ganglia may play an important role in the dysfunctional emotional processing and regulation of BD patients ( 26 ). Nevertheless, whereas in this study the BGN is highlighted as the FBN that is more functionally abnormal in BD, in the literature it has been demonstrated that some other FBNs appear to be more relevant in BD, such as the default mode, central executive, and salience networks ( 25 ). Our results demonstrate that the ASN seems to be abnormal in BD, but we did not find any significant abnormalities related to executive control networks in our study.…”

“…Recently, Yoon et al ( 25 ) did a review study on altered functional connectivity in BD. They suggested that the pathophysiology of BD is influenced by disrupted intranetwork and internetwork functional connectivity.…”

Building bridges: simultaneous multimodal neuroimaging approaches for exploring the organization of brain networks

“…The potential impact of a better understanding of the BOLD signal is far-reaching given that this measure offers noninvasive whole-organ coverage and is widely used across species, thus providing a link between basic research and patient management. Further, there is significant evidence, although much of it is correlative, that brain network measures derived from BOLD contrast (i.e., functional connectivity) may have utility as a diagnostic and prognostic tool for a variety of neurological conditions as well as brain injuries and diseases (see select reviews by Wang et al, 57 Lunkova et al, 58 Harikumar et al, 59 Yoon et al, 60 and Kanel et al 61 ). The combination of fMRI with complementary modes not only helps discern what measures may be most useful clinically but also stands to yield mechanistic insight into the biology that underpins BOLD signal differences between individuals, populations, and time points.…”