Piccoli Tommaso, Valente Giancarlo, Linden David E J, Re Marta, Esposito Fabrizio, Sack Alexander T, Di Salle Francesco
Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, University of Maastricht, Maastricht, The Netherlands; Department of Biomedicine and Clinical Neuroscience, University of Palermo, Palermo, Italy.
Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, University of Maastricht, Maastricht, The Netherlands.
PLoS One. 2015 Apr 7;10(4):e0123354. doi: 10.1371/journal.pone.0123354. eCollection 2015.
The default mode network and the working memory network are known to be anti-correlated during sustained cognitive processing, in a load-dependent manner. We hypothesized that functional connectivity among nodes of the two networks could be dynamically modulated by task phases across time.
To address the dynamic links between default mode network and the working memory network, we used a delayed visuo-spatial working memory paradigm, which allowed us to separate three different phases of working memory (encoding, maintenance, and retrieval), and analyzed the functional connectivity during each phase within and between the default mode network and the working memory network networks.
We found that the two networks are anti-correlated only during the maintenance phase of working memory, i.e. when attention is focused on a memorized stimulus in the absence of external input. Conversely, during the encoding and retrieval phases, when the external stimulation is present, the default mode network is positively coupled with the working memory network, suggesting the existence of a dynamically switching of functional connectivity between "task-positive" and "task-negative" brain networks.
Our results demonstrate that the well-established dichotomy of the human brain (anti-correlated networks during rest and balanced activation-deactivation during cognition) has a more nuanced organization than previously thought and engages in different patterns of correlation and anti-correlation during specific sub-phases of a cognitive task. This nuanced organization reinforces the hypothesis of a direct involvement of the default mode network in cognitive functions, as represented by a dynamic rather than static interaction with specific task-positive networks, such as the working memory network.
已知默认模式网络和工作记忆网络在持续认知处理过程中以负荷依赖的方式呈反相关。我们假设，这两个网络节点之间的功能连接可能会随时间在任务阶段中动态调节。
为了研究默认模式网络和工作记忆网络之间的动态联系，我们采用了延迟视觉空间工作记忆范式，该范式使我们能够区分工作记忆的三个不同阶段（编码、维持和检索），并分析默认模式网络和工作记忆网络内部及之间在每个阶段的功能连接。
我们发现，这两个网络仅在工作记忆的维持阶段呈反相关，即当注意力集中在没有外部输入的记忆刺激上时。相反，在编码和检索阶段，当存在外部刺激时，默认模式网络与工作记忆网络呈正耦合，这表明在“任务积极”和“任务消极”脑网络之间存在功能连接的动态切换。
我们的结果表明，人类大脑中既定的二分法（休息时网络反相关，认知时激活-失活平衡）具有比以前认为的更细微的组织，并且在认知任务的特定子阶段参与不同的相关和反相关模式。这种细微的组织强化了默认模式网络直接参与认知功能的假设，表现为与特定任务积极网络（如工作记忆网络）的动态而非静态相互作用。
