Institut de Neurosciences de la Timone UMR 7289, Aix Marseille Université, CNRS, Marseille 13005, France.
Department of Neuroscience, Neurological Clinic, University of Padua, Padua, Italy; Padova Neuroscience Center, University of Padua, Padua, Italy.
Neuroimage Clin. 2021;32:102812. doi: 10.1016/j.nicl.2021.102812. Epub 2021 Sep 11.
Beyond causing local ischemia and cell damage at the site of injury, stroke strongly affects long-range anatomical connections, perturbing the functional organization of brain networks. Several studies reported functional connectivity abnormalities parallelling both behavioral deficits and functional recovery across different cognitive domains. FC alterations suggest that long-range communication in the brain is altered after stroke. However, standard FC analyses cannot reveal the directionality and time scale of inter-areal information transfer. We used resting-state fMRI and covariance-based Granger causality analysis to quantify network-level information transfer and its alteration in stroke. Two main large-scale anomalies were observed in stroke patients. First, inter-hemispheric information transfer was significantly decreased with respect to healthy controls. Second, stroke caused inter-hemispheric asymmetries, as information transfer within the affected hemisphere and from the affected to the intact hemisphere was significantly reduced. Both anomalies were more prominent in resting-state networks related to attention and language, and they correlated with impaired performance in several behavioral domains. Overall, our findings support the hypothesis that stroke provokes asymmetries between the affected and spared hemisphere, with different functional consequences depending on which hemisphere is lesioned.
除了在损伤部位引起局部缺血和细胞损伤外，中风还强烈影响远距离解剖连接，扰乱大脑网络的功能组织。几项研究报告称，功能连接异常与不同认知领域的行为缺陷和功能恢复平行。FC 改变表明中风后大脑的长程通讯发生了改变。然而，标准的 FC 分析不能揭示大脑区域之间信息传递的方向性和时间尺度。我们使用静息态 fMRI 和基于协方差的格兰杰因果分析来量化中风患者的网络级信息传递及其变化。在中风患者中观察到两个主要的大规模异常。首先，与健康对照组相比，半球间的信息传递明显减少。其次，中风导致了半球间的不对称，因为受影响半球内的信息传递以及从受影响半球到未受影响半球的信息传递明显减少。这两种异常在与注意力和语言相关的静息态网络中更为突出，并且与多个行为领域的受损表现相关。总的来说，我们的发现支持这样一种假设，即中风引起受影响和未受影响半球之间的不对称，而功能后果取决于哪个半球受损。
