轻度认知功能损害患者静息状态脑默认活动网络的功能磁共振研究

目的 采用静息状态功能磁共振(fMRI)技术,探讨轻度认知功能损害(MCI)患者的脑默认活动网络(DMN)是否存在异常及其可能的神经机制.方法 对20名遗忘型MCI老年患者和25名正常老年人进行简易智能状态检查(MMSE)、听觉词语学习测验(AVLT)和静息状态脑功能成像.利用低频振幅(ALFF)算法,观察MCI患者相对于正常老年人ALFF增强及减弱的区域.结果 MMSE和AVLT测试结果显示MCI患者与正常老年人比较,记忆功能损害较明显,主要以情景记忆的短延迟回忆(2.4±1.7)分与(6.6±1.4)分,t=3.70,P＜0.01]和长延迟回忆(2.1±1.6)分与(6.7±1.5)分,t=4.16,P＜0.01]损害为主.静息状态fMRI结果显示与正常老年人比较,MCI患者与情景记忆密切相关的海马、海马旁回和侧颞叶皮层等脑区的ALFF减弱(t=2.58、2.43、1.75,均P＜0.01),颞顶交界和顶下小叶的ALFF增强(t=3.14、2.77,均P＜0.01).结论 MCI患者静息状态DMN与情景记忆密切相关的脑区结点活动强度存在异常,与正常老年人比较,大多活动减低,但是部分区域活动增强,提示MCI患者脑内可能存在代偿机制.

Abstract：

Objective To explore the activity and its possible neural mechanism of brain default mode network by using resting state functional magnetic resonance imaging (fMRI) in patients with mild cognitive impairment (MCI). Methods The 20 amnestic MCI patients and 25 healthy controls were included in this study, and all subjects underwent mini-mental state examination (MMSE), auditory verbal learning test (AVLT) and fMRI. The data were analyzed by amplitude of low frequency fluctuation (ALFF), and the enhanced and weakened regions of ALFF were observed and compared in both MCI patients and healthy controls. Results MMSE and AVLT tests showed that the memory function was seriously impaired in MCI patients compared with healthy controls, which is based on the short and long delayed episodic memory impairment (2.4±1.7 vs. 6.6±1.4, t=3.70, P＜0.01; 2.1±1.6 vs. 6.7±1.5, t=4.16, P＜0.01). The resting state fMRI showed that MCI patients had significant decreases of ALFF in hippocampal formation, parahippocampal cortex and lateral temporal cortex as compared with health controls (t=2.58, 2.43 and 1.75, all P＜0.01), which were closely relevant to the episodic memory. And they had significant increases in temporal-parietal joint and inferior parietal lobule (t=3.14 and 2.77, both P＜0.01). Conclusions MCI patients show significant decreased active intensity of some DMN nodes that is related to episodic memory in resting state. Increased active intensity in MCI patients would be some type of compensation.

A functional magnetic resonance imaging study on resting state brain default mode network in patients with mild cognitive impairment

Objective To explore the activity and its possible neural mechanism of brain default mode network by using resting state functional magnetic resonance imaging (fMRI) in patients with mild cognitive impairment (MCI). Methods The 20 amnestic MCI patients and 25 healthy controls were included in this study, and all subjects underwent mini-mental state examination (MMSE), auditory verbal learning test (AVLT) and fMRI. The data were analyzed by amplitude of low frequency fluctuation (ALFF), and the enhanced and weakened regions of ALFF were observed and compared in both MCI patients and healthy controls. Results MMSE and AVLT tests showed that the memory function was seriously impaired in MCI patients compared with healthy controls, which is based on the short and long delayed episodic memory impairment (2.4±1.7 vs. 6.6±1.4, t=3.70, P＜0.01; 2.1±1.6 vs. 6.7±1.5, t=4.16, P＜0.01). The resting state fMRI showed that MCI patients had significant decreases of ALFF in hippocampal formation, parahippocampal cortex and lateral temporal cortex as compared with health controls (t=2.58, 2.43 and 1.75, all P＜0.01), which were closely relevant to the episodic memory. And they had significant increases in temporal-parietal joint and inferior parietal lobule (t=3.14 and 2.77, both P＜0.01). Conclusions MCI patients show significant decreased active intensity of some DMN nodes that is related to episodic memory in resting state. Increased active intensity in MCI patients would be some type of compensation.