Disrupted Regional Homogeneity in Melancholic and Non-melancholic Major Depressive Disorder at Rest

Abstract

Background: Melancholic depression has been viewed as one severe subtype of major depressive disorder (MDD). However, it is unclear whether melancholic depression has distinct changes in brain imaging. We aimed to explore specific or distinctive alterations in melancholic MDD and whether the alterations could be used to separate melancholic MDD from non-melancholic MDD or healthy controls. Materials and Methods: Thirty-one outpatients with melancholic MDD and thirty-three outpatients with non-melancholic MDD and thirty-two age- and gender-matched healthy controls were recruited. All participants were scanned by resting-state functional magnetic resonance imaging (fMRI). Imaging data were analyzed with the regional homogeneity (ReHo) and support vector machine (SVM) methods. Results: Melancholic MDD patients exhibited lower ReHo in the right superior occipital gyrus/middle occipital gyrus than non-melancholic MDD patients and healthy controls. Merely for non-melancholic MDD patients, decreased ReHo in the right middle frontal gyrus was negatively correlated with the total HRSD-17 scores. SVM analysis results showed that a combination of abnormal ReHo in the right fusiform gyrus/cerebellum Crus I and the right superior occipital gyrus/middle occipital gyrus exhibited the highest accuracy of 83.05% (49/59), with a sensitivity of 90.32% (28/31), and a specificity of 75.00% (21/28) for discriminating patients with melancholic MDD from patients with non-melancholic MDD. And a combination of abnormal ReHo in the right fusiform gyrus/cerebellum VI and left postcentral gyrus/precentral gyrus exhibited the highest accuracy of 98.41% (62/63), with a sensitivity of 96.77% (30/31), and a specificity of 100.00%(32/32) for separating patients with melancholic MDD from healthy controls. Conclusion: Our findings showed the distinctive ReHo pattern in patients with melancholic MDD and found brain area that may be associated with the pathophysiology of non-melancholic MDD. Potential imaging markers for discriminating melancholic MDD from non-melancholic MDD or healthy controls were reported.

Keywords: magnetic resonance imaging; melancholic depression; non-melancholic depression; regional homogeneity; resting state.

Figure 1

Brain regions showing group differences of ReHo values across three groups. Color bar indicates F values from ANCOVA (age, years of education and framewise displacement as covariates). ReHo, regional homogeneity; ANCOVA, analysis of covariance.

Figure 2

Statistical map depicts higher and lower ReHo of melancholic MDD patients compared with non-melancholic MDD patients. The threshold was set at p < 0.05. Blue denotes lower ReHo and red denotes higher ReHo. Color bar indicates T values from post-hoc t-tests. L, left side; R, right side; ReHo, regional homogeneity.

Figure 3

Statistical map depicts higher and lower ReHo of melancholic MDD patients compared with healthy controls. The threshold was set at p < 0.05. Blue denotes lower ReHo and red denotes higher ReHo. Color bar indicates T values from post-hoc t-tests. L, left side; R, right side; ReHo, regional homogeneity.

Figure 4

Statistical map depicts higher ReHo of non-melancholic MDD patients compared with healthy controls. The threshold was set at p < 0.05. Red denotes higher ReHo. Color bar indicates T values from post-hoc t-tests. L, left side; R, right side; ReHo, regional homogeneity.

Figure 5

Visualization of classifications through support vector machine (SVM) using the combination of ReHo values in the right fusiform gyrus/cerebellum Crus I and the right superior occipital gyrus/middle occipital gyrus to discriminate melancholic MDD and non-melancholic MDD. Left: SVM parameters result of 3D view. Right: dimension 1 and dimension 2 represent the ReHo values in the right fusiform gyrus/cerebellum Crus I and the right superior occipital gyrus/middle occipital gyrus, respectively. Red crosses represent non-melancholic MDD patients, and green crosses represent the melancholic MDD patients. MDD, major depression disorder.

Figure 6

The accuracy of using abnormal ReHo in different brain regions to classify patients with melancholic and non-melancholic MDD. 1, Right Middle Frontal Gyrus; 2, Right Fusiform Gyrus/Cerebellum Crus I; 3, Right Superior Occipital Gyrus/Middle Occipital Gyrus; 12, Right Middle Frontal Gyrus and Right Fusiform Gyrus/Cerebellum Crus I; 13, Right Middle Frontal Gyrus and Right Superior Occipital Gyrus/Middle Occipital Gyrus; 23, Right Fusiform Gyrus/Cerebellum Crus I and Right Superior Occipital Gyrus/Middle Occipital Gyrus; 123, Right Middle Frontal Gyrus and Right Fusiform Gyrus/Cerebellum Crus I and Right Superior Occipital Gyrus/Middle Occipital Gyrus.

Figure 7

Visualization of classifications through support vector machine (SVM) using the combination of ReHo values in the right fusiform gyrus/cerebellum VI and left postcentral gyrus/precentral gyrus to discriminate melancholic MDD and from controls. Left: SVM parameters result of 3D view. Right: dimension 1 and dimension 2 represent the ReHo values in the right fusiform gyrus/cerebellum VI and left postcentral gyrus/precentral gyrus, respectively. Red crosses represent healthy controls, and green crosses represent the melancholic MDD patients. MDD, major depression disorder.

Figure 8

Visualization of classifications through support vector machine (SVM) using the increased ReHo values in the right middle temporal gyrus to discriminate non-melancholic MDD patients from healthy controls. Left: SVM parameters result of 3D view. Right: Classified map of the ReHo values in the right middle temporal gyrus. MDD, major depressive disorder.