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Background: Patients with major depressive disorder (MDD) can frequently develop new depressive episodes after remission. However, the neural mechanisms underlying the increased risk for depressive relapse remain unclear. Herein, we aimed to explore whether the specific changes to regional and inter-regional spontaneous brain activities within DMN are associated with the course of episodes in pooled MDD patients.Methods: Resting-state functional magnetic resonance imaging was performed on patients with single-episode MDD (SEMDD, n = 30) and multiple-episode MDD (MEMDD, n = 54), and 71 age-, gender-, and educational level-matched healthy controls (HCs). We then accessed the differences in both the fractional amplitude of low-frequency fluctuations (fALFF) and functional connectivity by using the right precuneus as the seed among different groups.Results: Compared to the MEMDD and HC groups, the SEMDD group exhibited increased fALFF values in the right subgenual anterior cingulate cortex and right middle temporal gyrus. Decreased fALFF values in the right thalamus in the MEMDD group were also identified relative to the SEMDD and HC group. The peak values of fALFF in the right precuneus showed a negative correlation with the number of depressive episodes across the entire pool of MDD patients. No correlation was identified between functional connectivity using the right precuneus as the seed and the number of depressive episodes for the pooled MDD patients.Limitations: Medication, a relatively small sample size, and hypothesis driven study.Conclusions: Our neuroimaging results identified depression relapse-associated neural signatures and also indicated the role of reduced emotional appraisals in the thalamus. It is now possible to believe that the regional activity not inter-regional connectivity within the DMN may be involved in the pathology of depression relapse. [ABSTRACT FROM AUTHOR]

Poor sleep and insomnia have been recognized to be strongly correlated with the development of depression. The exploration of the basic mechanism of sleep disturbance could provide the basis for improved understanding and treatment of insomnia and prevention of depression. In this study, 31 subjects with insomnia symptoms as measured by the Hamilton Rating Scale for Depression (HAMD-17) and 71 age- and gender-matched subjects without insomnia symptoms were recruited to participate in a clinical trial. Using resting-state functional magnetic resonance imaging (rs-fMRI), we examined the alterations in spontaneous brain activity between the two groups. Correlations between the fractional amplitude of low frequency fluctuations (fALFF) and clinical measurements (e.g., insomnia severity and Hamilton Depression Rating Scale [HAMD] scores) were also tested in all subjects. Compared to healthy participants without insomnia symptoms, participants with insomnia symptoms showed a decreased fALFF in the left ventral anterior insula, bilateral posterior insula, left thalamus, and pons but an increased fALFF in the bilateral middle occipital gyrus and right precentral gyrus. More specifically, a significant, negative correlation of fALFF in the left thalamus with early morning awakening scores and HAMD scores in the overall sample was identified. These results suggest that insomnia symptoms are associated with altered spontaneous activity in the brain regions of several important functional networks, including the insular cortex of the salience and the thalamus of the hyperarousal network. The altered fALFF in the left thalamus supports the “hyperarousal theory” of insomnia symptoms, which could serve as a biomarker for insomnia. [ABSTRACT FROM AUTHOR]

Of major depression patients, 29–66% show only partial remission on a single antidepressant trial. Such patients are characterized by residual depressive symptoms such as anhedonia, psychic anxiety, sleep disturbance, and cognitive dysfunction. Despite having a tremendous impact on outcomes such as future relapse, morbidity, and mortality, the neural mechanisms of partially remitted depression remain unclear. Using the amplitude of low-frequency fluctuations (ALFF) approach, we investigated the intrinsic neural oscillation alterations during resting state in partially remitted depression. A total of 23 partially remitted depression patients and 68 healthy controls underwent magnetic resonance imaging for functional imaging. We compared ALFF differences between groups as well as correlations between clinical measurements and ALFF in the brain regions showing significant group differences. Compared with healthy controls, partially remitted depression patients showed increased ALFF in the left ventral anterior insula, bilateral posterior insula, and bilateral supramarginal gyrus, and decreased ALFF in the left calcarine gyrus. A trend positive correlation between the number of depressive episodes and ALFF values was found in the right posterior insula in the partially remitted depression group. In addition, the ALFF in the right supramarginal gyrus were negatively correlated with Hamilton Depression Rating Scale scores. Consistent with the emerging theory of the role of the salience network in sensing the changes of homeostasis that contributes to partially remitted depression, the current findings suggest that the increased intrinsic neural oscillation of the insula is related to the refractoriness to treatment and may be an imaging marker for predicting future depression recurrence. [ABSTRACT FROM AUTHOR]