Theoretical and Computational Neuroscience Group, Center for Brain and Cognition, Universitat Pompeu Fabra, Barcelona, Spain.
Pharmacopsychiatry. 2012 May;45 Suppl 1:S57-64. doi: 10.1055/s-0032-1309001. Epub 2012 May 7.
During rest, the brain exhibits slow hemodynamic fluctuations (<0.1 Hz) that are correlated across spatially segregated brain regions, defining functional networks. Resting-state functional networks of people with schizophrenia were found to have graph properties that differ from those of control subjects. Namely, functional graphs from patients exhibit reduced small-worldness, increased hierarchy, lower clustering, improved efficiency and greater robustness. Notably, most of these parameters correlate with patients' cognitive performance.To test if a brain-wide coupling deficit could be at the origin of such network reorganization, we use a model of resting-state activity where the coupling strength can be manipulated. For a range of coupling values, the simulated functional graphs obtained were characterized using graph theory.For a coupling range, simulated graphs shared properties of healthy resting-state functional graphs. On decreasing the coupling strength, the resultant functional graphs exhibited a topological reorganization, in the same way as described in schizophrenia.This work shows how complex functional graph alterations reported in schizophrenia can be accounted for by a decrease in the structural coupling strength. These results are corroborated by reports of lower white matter density in schizophrenia.
在休息时，大脑会表现出缓慢的血液动力学波动（<0.1Hz），这些波动在空间上分隔的大脑区域之间相关，从而定义了功能网络。研究发现，精神分裂症患者的静息态功能网络具有与对照组不同的图性质。具体来说，患者的功能图表现出降低的小世界性、增加的层级结构、降低的聚类、提高的效率和更大的鲁棒性。值得注意的是，这些参数中的大多数与患者的认知表现相关。为了测试大脑广泛的耦合缺陷是否可能是这种网络重组的原因，我们使用了一种静息态活动模型，其中可以操纵耦合强度。对于一系列耦合值，使用图论对模拟得到的功能图进行了特征描述。对于一定的耦合范围，模拟的功能图具有健康静息状态功能图的属性。随着耦合强度的降低，所得的功能图表现出拓扑结构的重组，与精神分裂症中描述的方式相同。这项工作表明，通过降低结构耦合强度，如何解释精神分裂症中报道的复杂功能图改变。这些结果得到了精神分裂症中白质密度降低的报道的支持。
