Alpha-band fronto-limbic hyperconnectivity in adolescents with major depression and suicidal ideation

Fig. 1. Functional connectivity and between-group differences in the alpha band. (A) Functional connectivity networks in the alpha band (Top: SI-MDD; Middle: NSI-MDD; Bottom: HC); (B) Between-group difference networks (Top: SI-MDD vs. NSI-MDD; Middle: SI-MDD vs. HC; Bottom: NSI-MDD vs. HC); (C) Circos plot of the differential subnetwork identified by network-based statistics between adolescent MDD with and without SI. Nodes represent the AAL 90, and edges indicate functional connections showing significant between-group differences (generated using the Circos package in Python 3.8); (D) Three-dimensional spatial distribution of the differential subnetwork corresponding to panel C (generated using the BrainNet Viewer package in MATLAB R2021b). The three most highly connected regions (degree) within the alpha-band functional subnetwork that differentiated SI-MDD from NSI-MDD adolescents were (E) OLF.R; (F) SFGmed.R, and (G) ORBmid.R. The numeric labels in the figure correspond to individual brain regions, with details provided in Supplementary Table 1. AAL90, regions of the Automated Anatomical Labeling 90; HC, Health control; MDD, major depressive disorder; OLF.R, right olfactory cortex;…

Fig. 2. Global network topology across sparsity. Comparison of (A) Global efficiency; (B) Local efficiency; (C) Lambda; (D) Gamma, and (E) Sigma among HC, SI-MDD, and NSI-MDD groups. Triangular markers along the x-axis indicate specific sparsity levels at which significant between-group differences were observed. In panels D and E, significant differences between HC and NSI-MDD were exclusively observed at 5% sparsity. HC, healthy controls; NSI-MDD, major depressive disorder without suicidal ideation; SI-MDD, major depressive disorder with suicidal ideation

Fig. 3. Nodal topological properties of key nodes. Local network topological properties of the three core brain regions identified from the alpha-band enhanced functional connectivity network: OLF.R, SFGmed.R, and ORBmid.R. The following nodal metrics were compared among healthy controls, MDD without SI, and MDD with SI: (A) Degree centrality, indicating the number of direct connections; (B) Betweenness centrality, representing the hub role in network information transfer; (C) Nodal efficiency, reflecting global information exchange capacity; (D) Local nodal efficiency, describing information processing capability within the local neighborhood. (* p < 0.05, ** p < 0.01, *** p < 0.001). MDD, major depressive disorder; OLF.R, right olfactory cortex; ORBmid.R, right middle orbital gyrus; SFGmed.R, right medial superior frontal gyrus; SI, suicidal ideation

Fig. 4. Correlations between nodal properties and HAMD scores. HAMD scores negatively correlated with (A) nodal efficiency (ACG.R), (B) degree centrality (ACG.R), and (C) betweenness centrality (DCG.R) in the SI-MDD group, while positively correlating with (D) local efficiency in the THA.R in the NSI-MDD group. Given the exploratory nature of these analyses, no correction for multiple comparisons was applied. ACG.R, right anterior cingulate gyrus; DCG.R, right dorsal cingulate gyrus; HAMD, Hamilton Depression Rating Scale; MDD, major depressive disorder; SI, suicidal ideation; THA.R, right thalamus