Center for Mind/Brain Sciences (CIMeC), University of Trento, 38068 Rovereto, Italy.
Proc Natl Acad Sci U S A. 2014 Jan 28;111(4):E417-25. doi: 10.1073/pnas.1317267111. Epub 2014 Jan 13.
Which aspects of our sensory environment enter conscious awareness does not only depend on physical features of the stimulus, but also critically on the so-called current brain state. Results from magnetoencephalography/EEG studies using near-threshold stimuli have consistently pointed to reduced levels of α- (8-12 Hz) power in relevant sensory areas to predict whether a stimulus will be consciously perceived or not. These findings have been mainly interpreted in strictly "local" terms of enhanced excitability of neuronal ensembles in respective cortical regions. The present study aims to introduce a framework that complements this rather local perspective, by stating that the functional connectivity architecture before stimulation will predetermine information flow. Thus, information computed at a local level will be distributed throughout a network, thereby becoming consciously accessible. Data from a previously published experiment on conscious somatosensory near-threshold perception was reanalyzed focusing on the prestimulus period. Analysis of spectral power showed reduced α-power mainly in the contralateral S2 and middle frontal gyrus to precede hits, thus overall supporting the current literature. Furthermore, differences between hits and misses were obtained on global network (graph theoretical) features in the same interval. Most importantly, in accordance with our framework, we could show that the somatosensory cortex is "more efficiently" integrated into a distributed network in the prestimulus period. This finding means that when a relevant sensory stimulus impinges upon the system, it will encounter preestablished pathways for information flow. In this sense, prestimulus functional connectivity patterns form "windows" to conscious perception.
我们的感官环境的哪些方面进入意识不仅取决于刺激的物理特征，还取决于所谓的当前大脑状态。使用近阈值刺激的脑磁图/脑电图研究的结果一致表明，相关感觉区域的α波（8-12 Hz）功率降低可预测刺激是否会被有意识地感知。这些发现主要从相应皮质区域中神经元集合的兴奋性增强的严格“局部”角度来解释。本研究旨在引入一个框架，通过指出刺激前的功能连接结构将预先确定信息流，从而补充这种相当局部的观点。因此，在局部水平上计算的信息将在网络中传播，从而变得可以有意识地访问。对先前发表的关于有意识的体感近阈值感知的实验数据进行了重新分析，重点是刺激前的时期。对光谱功率的分析表明，在击中之前，主要在对侧 S2 和中额回中出现α波功率降低，因此总体上支持当前文献。此外，在同一间隔内还获得了命中和未命中之间的全局网络（图论）特征差异。最重要的是，根据我们的框架，我们可以证明在刺激前时期，体感皮层被更有效地整合到分布式网络中。这一发现意味着，当一个相关的感觉刺激作用于系统时，它将遇到预先建立的信息流路径。从这个意义上说，刺激前的功能连接模式形成了意识感知的“窗口”。
