Ward Andrew M, Schultz Aaron P, Huijbers Willem, Van Dijk Koene R A, Hedden Trey, Sperling Reisa A
Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts; Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts.
Hum Brain Mapp. 2014 Mar;35(3):1061-73. doi: 10.1002/hbm.22234. Epub 2013 Feb 13.
The default-mode network (DMN) is a distributed functional-anatomic network implicated in supporting memory. Current resting-state functional connectivity studies in humans remain divided on the exact involvement of medial temporal lobe (MTL) in this network at rest. Notably, it is unclear to what extent the MTL regions involved in successful memory encoding are connected to the cortical nodes of the DMN during resting state. Our findings using functional connectivity MRI analyses of resting-state data indicate that the parahippocampal gyrus (PHG) is the primary hub of the DMN in the MTL during resting state. Also, connectivity of the PHG is distinct from connectivity of hippocampal regions identified by an associative memory-encoding task. We confirmed that several hippocampal encoding regions lack significant functional connectivity with cortical DMN nodes during resting state. Additionally, a mediation analysis showed that resting-state connectivity between the hippocampus and posterior cingulate cortex--a major hub of the DMN--is indirect and mediated by the PHG. Our findings support the hypothesis that the MTL memory system represents a functional subnetwork that relates to the cortical nodes of the DMN through parahippocampal functional connections.
默认模式网络（DMN）是一个与支持记忆有关的分布式功能-解剖网络。目前关于人类静息态功能连接性的研究，对于内侧颞叶（MTL）在静息状态下该网络的确切参与情况仍存在分歧。值得注意的是，尚不清楚参与成功记忆编码的MTL区域在静息状态下与DMN的皮质节点连接的程度。我们使用静息态数据的功能连接性MRI分析得出的结果表明，在静息状态下，海马旁回（PHG）是MTL中DMN的主要枢纽。此外，PHG的连接性与通过联想记忆编码任务确定的海马区域的连接性不同。我们证实，在静息状态下，几个海马编码区域与皮质DMN节点缺乏显著的功能连接。此外，一项中介分析表明，海马与后扣带回皮质（DMN的一个主要枢纽）之间的静息态连接是间接的，且由PHG介导。我们的研究结果支持这样一种假设，即MTL记忆系统代表一个功能子网，该子网通过海马旁回的功能连接与DMN的皮质节点相关。
