Becker Robert, Knock Stuart, Ritter Petra, Jirsa Viktor
Functional Brain Mapping Lab, University of Geneva, Geneva, Switzerland.
Institut de Neurosciences des Systèmes, Aix Marseille Université, Marseille, France.
PLoS Comput Biol. 2015 Sep 3;11(9):e1004352. doi: 10.1371/journal.pcbi.1004352. eCollection 2015 Sep.
Oscillations are ubiquitous phenomena in the animal and human brain. Among them, the alpha rhythm in human EEG is one of the most prominent examples. However, its precise mechanisms of generation are still poorly understood. It was mainly this lack of knowledge that motivated a number of simultaneous electroencephalography (EEG) - functional magnetic resonance imaging (fMRI) studies. This approach revealed how oscillatory neuronal signatures such as the alpha rhythm are paralleled by changes of the blood oxygenation level dependent (BOLD) signal. Several such studies revealed a negative correlation between the alpha rhythm and the hemodynamic BOLD signal in visual cortex and a positive correlation in the thalamus. In this study we explore the potential generative mechanisms that lead to those observations. We use a bursting capable Stefanescu-Jirsa 3D (SJ3D) neural-mass model that reproduces a wide repertoire of prominent features of local neuronal-population dynamics. We construct a thalamo-cortical network of coupled SJ3D nodes considering excitatory and inhibitory directed connections. The model suggests that an inverse correlation between cortical multi-unit activity, i.e. the firing of neuronal populations, and narrow band local field potential oscillations in the alpha band underlies the empirically observed negative correlation between alpha-rhythm power and fMRI signal in visual cortex. Furthermore the model suggests that the interplay between tonic and bursting mode in thalamus and cortex is critical for this relation. This demonstrates how biophysically meaningful modelling can generate precise and testable hypotheses about the underpinnings of large-scale neuroimaging signals.
振荡是动物和人类大脑中普遍存在的现象。其中，人类脑电图中的阿尔法节律是最突出的例子之一。然而，其精确的产生机制仍知之甚少。正是这种知识的匮乏推动了一些同步脑电图（EEG）-功能磁共振成像（fMRI）研究。这种方法揭示了诸如阿尔法节律等振荡神经元特征是如何与血氧水平依赖（BOLD）信号的变化并行的。几项此类研究揭示了视觉皮层中阿尔法节律与血液动力学BOLD信号之间的负相关以及丘脑的正相关。在本研究中，我们探讨导致这些观察结果的潜在生成机制。我们使用了一个能够产生爆发的斯特凡内斯库-吉尔萨3D（SJ3D）神经团块模型，该模型再现了局部神经元群体动力学的大量突出特征。我们构建了一个由耦合的SJ3D节点组成的丘脑-皮层网络，考虑了兴奋性和抑制性定向连接。该模型表明，皮层多单元活动（即神经元群体的放电）与阿尔法波段的窄带局部场电位振荡之间的负相关是视觉皮层中阿尔法节律功率与fMRI信号之间经验性观察到的负相关的基础。此外，该模型表明丘脑和皮层中紧张性和爆发模式之间的相互作用对于这种关系至关重要。这证明了具有生物物理意义的建模如何能够生成关于大规模神经成像信号基础的精确且可测试的假设。
