Fakhraei Leila, Francoeur Miranda, Balasubramani Pragathi P, Tang Tianzhi, Hulyalkar Sidharth, Buscher Nathalie, Mishra Jyoti, Ramanathan Dhakshin S
Mental Health Service, VA San Diego Healthcare System., La Jolla, CA 92161, USA.
Department of Psychiatry, UC San Diego, La Jolla, CA 92093, USA.
Cereb Cortex Commun. 2021 May 5;2(2):tgab034. doi: 10.1093/texcom/tgab034. eCollection 2021.
The default-mode network (DMN) in humans consists of a set of brain regions that, as measured with functional magnetic resonance imaging (fMRI), show both intrinsic correlations with each other and suppression during externally oriented tasks. Resting-state fMRI studies have previously identified similar patterns of intrinsic correlations in overlapping brain regions in rodents (A29C/posterior cingulate cortex, parietal cortex, and medial temporal lobe structures). However, due to challenges with performing rodent behavior in an MRI machine, it is still unclear whether activity in rodent DMN regions are suppressed during externally oriented visual tasks. Using distributed local field potential measurements in rats, we have discovered that activity in DMN brain regions noted above show task-related suppression during an externally oriented visual task at alpha and low beta-frequencies. Interestingly, this suppression (particularly in posterior cingulate cortex) was linked with improved performance on the task. Using electroencephalography recordings from a similar task in humans, we identified a similar suppression of activity in posterior cingulate cortex at alpha/low beta-frequencies. Thus, we have identified a common electrophysiological marker of DMN suppression in both rodents and humans. This observation paves the way for future studies using rodents to probe circuit-level functioning of DMN function.
Here we show that alpha/beta frequency oscillations in rats show key features of DMN activity, including intrinsic correlations between DMN brain regions, task-related suppression, and interference with attention/decision-making. We found similar task-related suppression at alpha/low beta-frequencies of DMN activity in humans.
人类的默认模式网络（DMN）由一组脑区组成，通过功能磁共振成像（fMRI）测量发现，这些脑区彼此之间存在内在相关性，并且在外部导向任务期间会受到抑制。静息态fMRI研究此前已在啮齿动物的重叠脑区（A29C/后扣带回皮层、顶叶皮层和内侧颞叶结构）中发现了类似的内在相关性模式。然而，由于在MRI机器中对啮齿动物进行行为测试存在挑战，目前尚不清楚在外部导向的视觉任务期间，啮齿动物DMN区域的活动是否会受到抑制。通过对大鼠进行分布式局部场电位测量，我们发现上述DMN脑区的活动在外部导向的视觉任务期间，在α和低β频率下表现出与任务相关的抑制。有趣的是，这种抑制（尤其是在后扣带回皮层）与任务表现的改善有关。通过对人类进行类似任务的脑电图记录，我们在人类后扣带回皮层中也发现了α/低β频率下类似的活动抑制。因此，我们在啮齿动物和人类中都发现了DMN抑制的一个共同电生理标志物。这一观察结果为未来利用啮齿动物研究DMN功能的电路水平功能铺平了道路。
我们在此表明，大鼠的α/β频率振荡表现出DMN活动的关键特征，包括DMN脑区之间的内在相关性、与任务相关的抑制以及对注意力/决策的干扰。我们在人类中也发现了DMN活动在α/低β频率下类似的与任务相关的抑制。
