Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway.
Division of Psychiatry, Haukeland University Hospital, Bergen, Norway.
PLoS One. 2019 Sep 19;14(9):e0218358. doi: 10.1371/journal.pone.0218358. eCollection 2019.
Using fMRI, Hugdahl et al. (2015) reported the existence of a general-domain cortical network during active task-processing which was non-specific to the cognitive task being processed. They labelled this network the extrinsic mode network (EMN). The EMN would be predicted to be negatively, or anti-correlated with the classic default mode network (DMN), typically observed during periods of rest, such that while the EMN should be down-regulated and the DMN up-regulated in the absence of demands for task-processing, the reverse should occur when demands change from resting to task-processing. This would require alternating periods of task-processing and resting and analyzing data continuously when demands change from active to passive periods and vice versa. We were particularly interested in how the networks interact in the critical transition points between conditions. For this purpose, we used an auditory task with multiple cognitive demands in a standard fMRI block-design. Task-present (ON) blocks were alternated with an equal number of task-absent, or rest (OFF) blocks to capture network dynamics across time and changing environmental demands. To achieve this, we specified the onset of each block, and used a finite-impulse response function (FIR) as basis function for estimation of the fMRI-BOLD response. During active (ON) blocks, the results showed an initial rapid onset of activity in the EMN network, which remained throughout the period, and faded away during the first scan of the OFF-block. During OFF blocks, activity in the DMN network showed an initial time-lag where neither the EMN nor the DMN was active, after which the DMN was up-regulated. Studying network dynamics in alternating passive and active periods may provide new insights into brain network interaction and regulation.
使用 fMRI，Hugdahl 等人（2015 年）报告了在主动任务处理过程中存在一个一般领域的皮质网络，该网络与正在处理的认知任务无关。他们将这个网络命名为外在模式网络（EMN）。EMN 预计与经典的默认模式网络（DMN）呈负相关或反相关，通常在休息期间观察到，因此，当没有任务处理需求时，EMN 应该下调，DMN 应该上调，而当需求从休息转变为任务处理时，情况应该相反。这需要交替进行任务处理和休息，并在需求从主动转变为被动或反之亦然时连续分析数据。我们特别感兴趣的是网络在条件之间的关键转换点如何相互作用。为此，我们在标准 fMRI 块设计中使用了具有多种认知需求的听觉任务。任务呈现（ON）块与数量相等的任务缺失或休息（OFF）块交替出现，以捕获随时间和变化的环境需求的网络动态。为此，我们指定了每个块的起始时间，并使用有限脉冲响应函数（FIR）作为基础函数来估计 fMRI-BOLD 响应。在活动（ON）块期间，结果显示 EMN 网络的活动初始快速出现，并且在整个期间保持不变，并且在 OFF 块的第一个扫描期间消失。在 OFF 块期间，DMN 网络的活动显示出初始的时间滞后，在此期间 EMN 和 DMN 都不活跃，之后 DMN 被上调。研究交替的被动和主动时期的网络动态可能为大脑网络相互作用和调节提供新的见解。
