The Brain Dynamics Centre, Sydney Medical School-Westmead and Westmead Millennium Institute for Medical Research, Sydney; Discipline of Psychiatry, University of Sydney Medical School: Western, Westmead Hospital, Sydney.
Monash Clinical and Imaging Neuroscience, School of Psychology and Psychiatry & Monash Biomedical Imaging, Monash University, Clayton, Victoria, Australia.
Biol Psychiatry. 2014 Oct 1;76(7):567-74. doi: 10.1016/j.biopsych.2014.02.018. Epub 2014 Mar 6.
Major depressive disorder (MDD) has been shown to be associated with a disrupted topological organization of functional brain networks. However, little is known regarding whether these changes have a structural basis. Diffusion tensor imaging (DTI) enables comprehensive whole-brain mapping of the white matter tracts that link regions distributed throughout the entire brain, the so-called human connectome.
We examined whole-brain structural networks in a cohort of 95 MDD outpatients and 102 matched control subjects. Structural networks were represented by an 84 × 84 connectivity matrix representing probabilistic white matter connections between 84 parcellated cortical and subcortical regions using DTI tractography. Network-based statistics were used to assess differences in the interregional connectivity matrix between the two groups, and graph theory was used to examine overall topological organization.
Our network-based statistics analysis demonstrates lowered structural connectivity within two distinct brain networks that are present in depression: the first primarily involves the regions of the default mode network and the second comprises the frontal cortex, thalamus, and caudate regions that are central in emotional and cognitive processing. These two altered networks were observed in the context of an overall preservation of topology as reflected as no significant group differences for the graph-theory measures.
This is the first report to use DTI to show the structural connectomic alterations present in MDD. Our findings highlight that altered structural connectivity between nodes of the default mode network and the frontal-thalamo-caudate regions are core neurobiological features associated with MDD.
重度抑郁症（MDD）与功能性大脑网络的拓扑组织紊乱有关。然而，对于这些变化是否具有结构基础，我们知之甚少。弥散张量成像（DTI）能够全面映射连接整个大脑分布区域的白质束，即所谓的人类连接组。
我们检查了 95 名 MDD 门诊患者和 102 名匹配对照者的全脑结构网络。结构网络由一个 84×84 的连接矩阵表示，该矩阵代表 84 个皮质和皮质下区域之间的概率性白质连接，使用 DTI 轨迹法。网络统计用于评估两组间区域间连接矩阵的差异，图论用于检查整体拓扑组织。
我们的网络统计分析表明，在抑郁症中存在两个不同的大脑网络的结构连接降低：第一个主要涉及默认模式网络的区域，第二个包括额叶皮层、丘脑和尾状核区域，这些区域在情绪和认知处理中起核心作用。在整体拓扑保持不变的情况下观察到这两个改变的网络，因为图论测量没有显示出显著的组间差异。
这是首次使用 DTI 显示 MDD 中存在的结构连接组改变的报告。我们的研究结果表明，默认模式网络和额-丘脑-尾状核区域节点之间的结构连接改变是与 MDD 相关的核心神经生物学特征。
