Many studies have found that the hippocampus plays a very important role in major depressive disorder (MDD). The hippocampus can be divided into three subfields: the cornu ammonis (CA), dentate gyrus (DG) and subiculum. Each subfield of the hippocampus has a unique function and are differentially associated with the pathological mechanisms of MDD. However, no research exists to describe the resting state functional connectivity of each hippocampal subfield in MDD. Fifty-five patients with MDD and 25 healthy controls (HCs) matched for gender, age and years of education were obtained. A seed-based method that imposed a template on the whole brain was used to assess the resting-state functional connectivity (rsFC) of each hippocampal subfield. Patients with MDD demonstrated increased connectivity in the left premotor cortex (PMC) and reduced connectivity in the right insula with the CA seed region. Increased connectivity was reported in the left orbitofrontal cortex (OFC) and left ventrolateral prefrontal cortex (vlPFC) with the DG seed region. The subiculum seed region revealed increased connectivity with the left premotor cortex (PMC), the right middle frontal gyrus (MFG), the left ventrolateral prefrontal cortex (vlPFC) and reduced connectivity with the right insula. ROC curves confirmed that the differences between groups were statistically significant. The results suggest that the CA, DG and subiculum have significant involvement with MDD. Specifically, the abnormal functional connectivity of the CA may be related to bias of coding and integration of information in patients with MDD. The abnormal functional connectivity of the DG may be related to the impairment of working memory in patients with MDD, and the abnormal functional connectivity of the subiculum may be related to cognitive impairment and negative emotions in patients with MDD.

中文翻译：

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重度抑郁症患者海马亚区的静息状态功能连接异常。

许多研究发现，海马在重度抑郁症（MDD）中起着非常重要的作用。海马可分为三个子域：角膜氨化（CA），齿状回（DG）和下丘脑。海马的每个子域具有独特的功能，并与MDD的病理机制有差异。但是，尚无描述MDD中每个海马亚区的静止状态功能连通性的研究。获得了针对性别，年龄和受教育年限相匹配的55名MDD患者和25个健康对照（HCs）。基于种子的方法在整个大脑上强加了模板，用于评估每个海马亚区的静止状态功能连接性（rsFC）。MDD患者表现出左前运动皮层（PMC）的连通性增加，而右岛与CA种子区的连通性降低。据报道，与DG种子区相比，左眶额叶皮层（OFC）和左腹外侧前额叶皮层（vlPFC）的连接性增加。下丘脑种子区显示出与左前运动皮层（PMC），右中额额回（MFG），左前外侧前额叶皮层（vlPFC）的连通性增加以及与右岛的连通性降低。ROC曲线证实两组之间的差异具有统计学意义。结果表明，CA，DG和下丘脑与MDD密切相关。特别，CA的功能异常连接可能与MDD患者的编码偏倚和信息整合有关。DG的功能连通性异常可能与MDD患者的工作记忆障碍有关，而亚下颌的功能连通性异常可能与MDD患者的认知障碍和负面情绪有关。