Data_Sheet_1_Aberrant Inter-hemispheric Connectivity in Patients With Recurrent Major Depressive Disorder: A Multimodal MRI Study.docx

ObjectiveInter-hemispheric network dysconnectivity has been well-documented in patients with recurrent major depressive disorder (MDD). However, it has remained unclear how structural networks between bilateral hemispheres relate to inter-hemispheric functional dysconnectivity and depression severity in MDD. Our study attempted to investigate the alterations in corpus callosum macrostructural and microstructural as well as inter-hemispheric homotopic functional connectivity (FC) in patients with recurrent MDD and to determine how these alterations are related with depressive severity.
Materials and MethodsResting-state functional MRI (fMRI), T1WI anatomical images and diffusion tensor MRI of the whole brain were performed in 140 MDD patients and 44 normal controls matched for age, sex, years of education. We analyzed the macrostructural and microstructural integrity as well as voxel-mirrored homotopic functional connectivity (VMHC) of corpus callosum (CC) and its five subregion. Two-sample t-test was used to investigate the differences between the two groups. Significant subregional metrics were correlated with depression severity by spearman's correlation analysis, respectively.
ResultsCompared with control subjects, MDD patients had significantly attenuated inter-hemispheric homotopic FC in the bilateral medial prefrontal cortex, and impaired anterior CC microstructural integrity (each comparison had a corrected P < 0.05), whereas CC macrostructural measurements remained stable. In addition, disruption of anterior CC microstructural integrity correlated with a reduction in FC in the bilateral medial prefrontal cortex, which correlated with depression severity in MDD patients. Furthermore, disruption of anterior CC integrity exerted an indirect influence on depression severity in MDD patients through an impairment of inter-hemispheric homotopic FC.
ConclusionThese findings may help to advance our understanding of the neurobiological basis of depression by identifying region-specific interhemispheric dysconnectivity.

研究目的：反复发作性重性抑郁障碍（Major Depressive Disorder，MDD）患者的半球间网络连接异常已被大量文献证实，但双侧大脑半球结构网络与半球间功能连接（Functional Connectivity，FC）异常及抑郁严重程度之间的关联机制仍不明确。本研究旨在探讨反复发作性MDD患者胼胝体（Corpus Callosum，CC）的宏观结构、微观结构以及半球间同源性功能连接的改变，并明确这些改变与抑郁严重程度的相关性。
材料与方法：本研究纳入140例反复发作性MDD患者及44例年龄、性别、受教育年限相匹配的正常对照者，对所有受试者进行静息态功能磁共振成像（functional Magnetic Resonance Imaging，fMRI）、T1加权解剖成像（T1WI）及全脑弥散张量磁共振成像扫描。我们分析了胼胝体及其5个子区域的宏观结构、微观结构完整性以及体素镜像同伦功能连接（Voxel-mirrored homotopic functional connectivity，VMHC）。采用两样本t检验比较两组间的差异，通过斯皮尔曼相关性分析分别探究存在组间差异的亚区指标与抑郁严重程度的相关性。
研究结果：与正常对照者相比，MDD患者双侧内侧前额叶皮层的半球间同源性功能连接显著减弱，且前胼胝体微观结构完整性受损（所有比较校正后P<0.05），而胼胝体宏观结构测量值无显著变化。此外，前胼胝体微观结构完整性受损与双侧内侧前额叶皮层的功能连接减弱相关，而该功能连接减弱又与MDD患者的抑郁严重程度相关。进一步分析发现，前胼胝体完整性受损可通过损害半球间同源性功能连接，间接影响MDD患者的抑郁严重程度。
结论：本研究结果明确了特异性脑区的半球间连接异常，有助于加深对抑郁症神经生物学基础的理解。