认知与发展心理学研究室知识库

目的：情节记忆是受老化影响最严重的认知功能之一。老年人情节记忆功能衰退主要表现为联结记忆成绩的下降。回想过程受损以及前额叶相关的脑网络功能衰退是老年人联结记忆损伤的潜在原因。可喜的是，老年人的认知能力以及大脑功能保留了极大的可塑性。重复经颅磁刺激(rTMS)作为一种无创性的脑刺激技术，能够直接调节目标脑区的可塑性，从而为改善老年人的联结记忆成绩以及提升其脑功能提供了可能。本论文通过三项研究，考察了rTMS干预能否改善认知正常的老年人的联结记忆成绩，以及其潜在的认知神经机制，系统地探讨了rTMS对健康老年人认知功能以及大脑可塑性的促进作用。
方法：基于随机控制设计，对实验组健康老年人的右半球背外侧前额叶(rDLPFC)施加10 Hz的为期两周总共10次的rTMS干预，研究一采用联想学习测验，考察rTMS干预对老年人联结记忆的促进作用，以及干预效应的保持性；研究二采用来源记忆范式，结合ERP技术，以ERP新旧效应为指标，考察rTMS干预促进老年人联结记忆的提取机制；研究三采用fMRI技术考察rTMS干预促进老年人联结记忆的脑神经机制。
结果：研究一发现，rTMS干预组老年人的联结记忆后测成绩显著高于前测，而控制组却不存在该效应；一个月后的追踪结果显示，干预组老年人的干预效应保持较好；研究二的ERPs结果显示，相对于控制组，rTMS干预组老年人在来源记忆提取阶段，与回想相关的左顶新旧效应在干预前后无显著变化，但与基于知觉信息的策略提取相关的负性新旧效应在rTMS干预之后增强；研究三发现rTMS干预导致老年人在rDLPFC与默认网络、海马旁回以及脑岛之间的大尺度脑功能连接上发生变化，且rDLPFC与默认网络之间的功能连接在rTMS干预前后的变化对老年人联结记忆成绩的提升有显著贡献。
结论：rTMS干预可以改善老年人的联结记忆成绩，这一促进效应至少可以保持一个月；rTMS干预能够促使老年人更好地使用基于知觉性信息的提取策略；rTMS干预可以调节老年人背外侧前额叶相关大尺度脑网络的功能连接，进而改善其联结记忆成绩。本论文对于使用rTMS提升老年人联结记忆成绩并改善其大脑功能具有重要启示。

Objective:Episodic memory is one of the cognitive domains that are vulnerable to aging. It included both item memory and associative memory. The associative memory demonstrated larger age effect than item memory, which might resulted from the deficit of the recollection as well as the disruption of the coordinated activity of large-scale brain networks. Luckily, the brain plasticity could be modulated to compensate for the cognitive decline. The repetitive transcranial magnetic stimulation (rTMS), a relatively noninvasive neuromodulatory technique, could directly modulate neural excitability in the stimulated cortical areas. The rTMS-altered neural activity could produce brain plastic changes, which is suggested to provide possibilities to alleviate cognitive decline. Here we are interested in whether the application of rTMS could reduce the associative deficit in the older adults who are cognitively intact. In addition, we also would like to explore the underlying neurocognitive mechanism of the rTMS effect on the associative memory in older adults.
Methods:This is a randomized controlled traildesign, with the intervention group received 10 sessions of 10 Hz rTMS applying on the right dorsolateral prefrontal cortex (rDLPFC), and the control group received 10 sessions of sham stimulation. The first study explored the rTMS effect on the associative memory performance as well as its maintenance effect. The second study explored the rTMS effect on the process of associative memory retrieval qualified by the ERPs old/new effects. The third study exploit the resting-state functional magnetic resonance imaging (fMRI) to explore the neural mechanism of rTMS-related associative memory enhancement.
Results:In study 1, behavioralresults showed that comparing with the control group, the rTMS significantly increased the associative memory performance and the enhanced effect still could be detected one month after the last stimulation session. In study 2, behavioral results showed that the rTMS significantly increased the source memory performance; the ERP results showed that during the retrieval phase, in comparisonwith the control group, the rTMS significantly increased the negative old/new effect which reflected the search and/oractivation of sensory-based information, rather than the left parietal old/new effectwhich reflected the process of recollection. In study 3, results showed that the large-scale network interactions among the rDLPFC and regions within the default mode network were modulated by the rTMS, which significantly contributed to the associative memory improvement.
Conclusions:These results suggest that rTMS could improve associative memory performance in the healthy older adults and the enhancement lasted for one month; the rTMS intervention facilitate the older adults to rely on the sensory-based information in retrieving source information in order to optimize their memory performance; the rTMS altered the large-scale brain network plasticity, which might underlie the associative memory improvement.