Mevel K, Grassiot B, Chételat G, Defer G, Desgranges B, Eustache F
Inserm-EPHE, unité U923, laboratoire de neuropsychologie, GIP Cyceron, université de Caen -Basse-Normandie, and Department of neurology, CHU Côte de Nacre, 14033 Caen cedex, France.
Rev Neurol (Paris). 2010 Nov;166(11):859-72. doi: 10.1016/j.neurol.2010.01.008. Epub 2010 Mar 11.
A "resting state" or "default mode network" has been highlighted in functional neuroimaging studies as a set of brain regions showing synchronized activity at rest or in task-independent cognitive state.
A considerable and increasing number of studies have been conducted over the last few years so as to unravel the cognitive function(s) of this brain network.
This review gives an overview of anatomical, physiological and phenomenological data regarding the default mode network. Different hypotheses have been proposed regarding the role of this network. Several studies have highlighted its involvement in autobiographical memory, prospection, self, attention, and theory of mind. The influence of the attention level and consciousness onto resting state brain network activity has also been discussed. Specific changes have been described in normal aging, Alzheimer's disease (AD) and multiple sclerosis (MS).
These studies altogether contribute to a better definition of the default mode network, in terms of implicated brain structures, subtending mechanisms, and potential cognitive roles. For instance, similarities and relationships were found between self-related brain activity and resting-state activity in regions belonging to this network, namely posterior cingulate and prefrontal areas that may reflect introspective activity experienced, more or less consciously, when the brain is not specifically engaged in a cognitive task. As a whole, the default mode network appears as a non human-specific intrinsic functional network, active all over the life from birth until aging where it is progressively modified, and sensitive to different pathologies including AD and MS. On the other hand, many points remain to be clarified concerning this network, such as the exact part of its activity dedicated to self-related cognitive processes (introspection, imaginary mental scenario based on past autobiographical experiences) and that involved in a sentinel-like attentional process designated to react to possible environmental events. Indeed, it seems that this network is functional even in case of low level of consciousness, i.e., during light sleep. Conversely, a loss of self and environment perception as in coma, deep sleep or anesthesia might modulate its connectivity along the anteroposterior axis, i.e., frontal activity disappearance associated with a parietal reinforcement of connectivity. Since studies aiming at highlighting these points are still uncommon to date, exhaustive and objective explorations are needed to better understand all these resting state processes.
在功能神经影像学研究中，“静息态”或“默认模式网络”被视为一组在静息状态或与任务无关的认知状态下显示同步活动的脑区。
在过去几年中，已经进行了大量且数量不断增加的研究，以揭示这个脑网络的认知功能。
本综述概述了关于默认模式网络的解剖学、生理学和现象学数据。关于这个网络的作用，已经提出了不同的假设。多项研究强调了它在自传体记忆、前瞻性思考、自我、注意力和心理理论方面的参与。还讨论了注意力水平和意识对静息态脑网络活动的影响。在正常衰老、阿尔茨海默病（AD）和多发性硬化症（MS）中已经描述了特定的变化。
这些研究共同有助于从涉及的脑结构、潜在机制和潜在认知作用等方面更好地定义默认模式网络。例如，在属于这个网络的区域，即后扣带回和前额叶区域，发现了自我相关脑活动与静息态活动之间的相似性和关系，这可能反映了大脑在未专门从事认知任务时或多或少有意识地体验到的内省活动。总体而言，默认模式网络似乎是一个非人类特有的内在功能网络，从出生到衰老在整个生命过程中都活跃，并且会逐渐改变，并且对包括AD和MS在内的不同病理状态敏感。另一方面，关于这个网络仍有许多问题有待澄清，例如其活动中专门用于自我相关认知过程（内省、基于过去自传体经历的想象心理场景）的确切部分，以及涉及对可能的环境事件做出反应的类似哨兵的注意力过程的部分。事实上，即使在意识水平较低的情况下，即浅睡眠期间，这个网络似乎也是有功能的。相反，如在昏迷、深度睡眠或麻醉中出现的自我和环境感知丧失可能会调节其沿前后轴的连接性，即额叶活动消失并伴有顶叶连接性增强。由于旨在突出这些要点的研究迄今为止仍然不常见，因此需要进行详尽且客观的探索，以更好地理解所有这些静息态过程。
