Decreased Functional Connectivity in Insular Subregions in Depressive Episodes of Bipolar Disorder and Major Depressive Disorder

Abstract

Objective: Clinically, it is very difficult to distinguish between major depressive disorder (MDD) and bipolar disorder (BD) in the period of depression. Increasing evidence shows that the insula plays an important role in depression. We aimed to compare the resting-state functional connectivity (rsFC) of insular subregions in patients with MDD and BD in depressive episodes (BDD), who had never experienced manic or hypomanic episodes when they were scanned to identify biomarkers for the identification of two diseases.Methods: We recruited 21 BDD patients, 40 MDD patients and 70 healthy controls (HC). Resting-state functional magnetic resonance imaging (rs-fMRI) was performed. BDD patients had never had manic or hypomanic episodes when they were scanned, and the diagnoses were determined by follow-up. We divided the insula into three parts including the ventral anterior insular cortex (v-AIN), dorsal anterior insular cortex (d-AIN), and posterior insula (PI). The insular-based rsFC was compared among the three groups, and an analysis of the correlation between the rsFC value and Hamilton depression and anxiety scales was carried out.Results: BDD and MDD patients demonstrated decreased rsFC from the v-AIN to the left superior/middle frontal gyrus compared with the HC group. Versus MDD and HC groups, BDD patients exhibited decreased rsFC from the v-AIN to the area in the left orbital frontal gyrus and left superior temporal gyrus (included temporal pole), from the PI to the right lateral postcentral gyrus and from all three insular subregions to the somatosensory and motor cortex. Meanwhile, a correlation between the rsFC value of the PI-right lateral postcentral gyrus and anxiety score was observed in patients.Conclusion: Our findings show BDD and MDD patients have similar decreases in insular connectivity in the dorsal lateral frontal regions, and BDD patients have specific decreased insular connectivity, especially in the somatosensory and motor cortex, which may be used as imaging evidence for clinical identification.

Validation of Chronic Restraint Stress Model in Young Adult Rats for the Study of Depression Using Longitudinal Multimodal MR Imaging

“…This is in accordance with previous studies reporting altered functional connectivity in both the salience and interoceptive networks in humans with depression compared to healthy individuals (Manoliu et al, 2014;Harshaw, 2015). For example, Yin et al (2018) observed decreased functional connectivity of insular cortex to somatosensory and motor cortices in patients with bipolar disorder in the period of depression.…”

Association between resting-state functional connectivity of amygdala subregions and peripheral pro-inflammation cytokines levels in bipolar disorder

“…Another fMRI study of BD also exhibited decreased FC from the amygdala to the TP, and this was consistent with our results [59]. Other several rs-fMRI studies have shown decreased FC of the TP in participants with psychiatric symptoms [60][61][62]. Other studies have shown TP abnormalities, including decreased gray matter density [63], reduced gray matter volume [64,65], lower mean diffusivity (re ects the microstructural integrity of white matter) [66], and decreased degree centrality (re ects the functional connections) [67] in BD patients.…”

<p>Disrupted Brain Entropy And Functional Connectivity Patterns Of Thalamic Subregions In Major Depressive Disorder</p>

“…The bilateral insular cortex is related to self-awareness and to the processing of emotional information, which are frequently affected in MDD 44. Previous MRI studies have reported that the insula could be a key region associated with depression 45,46. One possibility is that increased RSFC between the anterior thalamus and bilateral insula underlies emotion processing under MDD.…”