Yue Chunxian, Wu Di, Bai Feng, Shi Yongmei, Yu Hui, Xie Chunming, Zhang Zhijun
Department of Neurology, Affiliated ZhongDa Hospital, Neuropsychiatric Institute, Medical School, Southeast University, Nanjing, Jiangsu 210009, China.
Department of Neurology, Affiliated ZhongDa Hospital, Neuropsychiatric Institute, Medical School, Southeast University, Nanjing, Jiangsu 210009, China.
Behav Brain Res. 2015 Jul 15;288:94-102. doi: 10.1016/j.bbr.2015.04.013. Epub 2015 Apr 20.
Episodic memory (EM) dysfunction is a central characteristic of amnestic mild cognitive impairment (aMCI) subjects, and has a high risk of converting to Alzheimer's disease (AD). However, it is unknown how the EM network is modulated when a situation is switched. Twenty-six aMCI and twenty-two cognitively normal (CN) subjects were enrolled in this study. All of the subjects completed multi-dimensional neuropsychological tests and underwent functional magnetic resonance imaging scans during a resting-state and an episodic memory retrieval task state. The EM network was constructed using a seed-based functional connectivity (FC) approach. AMCI subjects showed poorer cognitive performances in the episodic memory and executive function. We demonstrated that connectivity of the left posterior parahippocampal gyrus (LpPHG) connected to the left ventral medial prefrontal cortex and the right postcentral gyrus (RPCG) was significantly decreased in aMCI subjects compared to CN subjects. Meanwhile, there was increased connectivity of the LpPHG to the right dorsal medial prefrontal cortex (RDMPFC), RPCG, left inferior parietal cortex, and bilateral superior parietal lobe in all of the subjects that changed from a resting-state to a task-state. Interestingly, the changed LpPHG-RDMPFC connectivity strength was significantly correlated with EM scores and executive function in the aMCI subjects. As a result, general brain regions are functionally organized and integrated into the EM network, and this strongly suggests that more cognitive resources are mobilized to meet the challenge of cognitive demand in the task state. These findings extend our understanding of the underlying mechanisms of EM deficits in aMCI subjects.
情景记忆（EM）功能障碍是遗忘型轻度认知障碍（aMCI）患者的核心特征，且具有较高的转化为阿尔茨海默病（AD）的风险。然而，尚不清楚当情境切换时，EM网络是如何被调节的。本研究纳入了26名aMCI患者和22名认知正常（CN）的受试者。所有受试者均完成了多维度神经心理学测试，并在静息状态和情景记忆检索任务状态下接受了功能磁共振成像扫描。采用基于种子点的功能连接（FC）方法构建EM网络。aMCI受试者在情景记忆和执行功能方面表现出较差的认知能力。我们发现，与CN受试者相比，aMCI受试者中连接左后海马旁回（LpPHG）与左腹内侧前额叶皮质和右中央后回（RPCG）的连接性显著降低。同时，在所有从静息状态转变为任务状态的受试者中，LpPHG与右背内侧前额叶皮质（RDMPFC）、RPCG、左下顶叶皮质和双侧上顶叶的连接性增加。有趣的是，aMCI受试者中LpPHG-RDMPFC连接强度的变化与EM评分和执行功能显著相关。结果表明，大脑一般区域在功能上被组织并整合到EM网络中，这强烈表明在任务状态下会调动更多认知资源来应对认知需求的挑战。这些发现扩展了我们对aMCI受试者EM缺陷潜在机制的理解。
