School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, USA.
Global Brain Health Institute, Trinity College Dublin, Dublin, Ireland; Trinity College Institute for Neuroscience, Trinity College Dublin, Dublin, Ireland; Lab for Clinical & Integrative Neuroscience, School of Psychology, Trinity College Dublin, Dublin, Ireland.
Brain Stimul. 2021 Jul-Aug;14(4):1005-1014. doi: 10.1016/j.brs.2021.06.007. Epub 2021 Jun 23.
Previous studies show that activity in the posterior default mode network (pDMN), including the posterior cingulate cortex and the precuneus, is correlated with the success of long-term episodic memory retrieval. However, the role of the anterior DMN (aDMN) including the medial prefrontal cortex is still unclear. Some studies show that activating the medial prefrontal cortex improves memory retrieval while other studies show deactivation of the medial prefrontal cortex in successful retrieval of episodic memories, suggesting a possible functional dissociation between the aDMN and pDMN.
In the current study, we aim to causally explore this probable dissociation using high-definition transcranial direct current stimulation (HD-tDCS).
We perform a randomised double-blinded two-visit placebo-controlled study with 84 healthy young adults. During Visit 1 they learn 75 Swahili-English word-associations. Seven days later, they randomly receive either anodal, cathodal or sham HD-tDCS targeting the pDMN or aDMN while they recall what they have previously learned.
We demonstrate that anodal stimulation of the pDMN and cathodal stimulation of the aDMN, equally improve the percentage of Swahili-English word-associations recalled 7 days after learning.
Modulating the activity in the aDMN and pDMN causally affect memory retrieval performance. HD-tDCS of the aDMN and pDMN shows that anodal stimulation of the pDMN and cathodal stimulation of the aDMN increases memory retrieval performance one week after the learning phase. Given consistent evidence, it is highly likely that we are increasing the activity in the pDMN with anodal pDMN stimulation. However, it is not clear if cathodal HD-tDCS targetting aDMN works via decoupling from the pDMN or via indirectly disinhibit pDMN.
先前的研究表明，后默认模式网络（pDMN）的活动，包括后扣带回皮质和楔前叶，与长期情景记忆检索的成功相关。然而，包括内侧前额叶皮质在内的前默认模式网络（aDMN）的作用仍不清楚。一些研究表明，激活内侧前额叶皮质可以改善记忆检索，而其他研究则表明，在成功检索情景记忆时，内侧前额叶皮质的去激活，这表明 aDMN 和 pDMN 之间可能存在功能分离。
在当前的研究中，我们旨在使用高清晰度经颅直流电刺激（HD-tDCS）来探索这种可能的分离。
我们进行了一项随机、双盲、两访、安慰剂对照研究，共纳入 84 名健康的年轻成年人。在第一次访问时，他们学习了 75 个斯瓦希里语-英语单词联想。七天后，他们随机接受 pDMN 或 aDMN 的阳极、阴极或假刺激，同时回忆他们之前所学的内容。
我们证明，pDMN 的阳极刺激和 aDMN 的阴极刺激同样可以提高学习 7 天后回忆的斯瓦希里语-英语单词联想的百分比。
调节 aDMN 和 pDMN 的活动可以对记忆检索表现产生因果影响。aDMN 和 pDMN 的 HD-tDCS 表明，pDMN 的阳极刺激和 aDMN 的阴极刺激可以在学习阶段一周后提高记忆检索表现。有一致的证据表明，我们极有可能通过阳极刺激 pDMN 来增加 pDMN 的活动。然而，尚不清楚阴极刺激 aDMN 是否通过与 pDMN 解耦或通过间接抑制 pDMN 来发挥作用。
