Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Sapienza University of Rome, Via A. Borelli 50, 00161, Rome, Italy.
Department of Neurology and Psychiatry, Sapienza University of Rome, Viale dell'Universit_a 30, 00185, Rome, Italy.
Brain Imaging Behav. 2018 Apr;12(2):467-476. doi: 10.1007/s11682-017-9715-x.
The anticorrelations in fMRI measurements are still not well characterized, but some new evidences point to a possible physiological role. We explored the topology of functional brain networks characterized by negative edgess and their possible alterations in schizophrenia, using functional images of 8 healthy subjects and 8 schizophrenic patients in a resting state condition. In order to minimize the insertion of artifactual negative correlations, the preprocessing of images was carried out by the CompCorr procedure, and the results compared with the Global Signal Regression (GSR) procedure. The degree distribution, the centrality, the efficiency and the rich-club behavior were used to characterize the functional brain network with negative links of healthy controls in comparison with schizophrenic patients. The results show that functional brain networks with both positive and negative values have a truncated power-law degree distribution. Moreover, although functional brain networks characterized by negative values have not small-world topology, they show a specific disassortative configuration: the more connected nodes tend to have fewer connections between them. This feature is lost using the GSR procedure. Finally, the comparison with schizophrenic patients showed a decreased (local and global) efficiency associated to a decreased connectivity among central nodes. As a conclusion, functional brain networks characterized by negative values, despite lacking a well defined topology, show specific features, different from random, and indicate an implication in the alterations associated to schizophrenia.
功能磁共振成像测量中的负相关仍然没有很好地描述，但一些新的证据指向可能的生理作用。我们使用 8 名健康受试者和 8 名精神分裂症患者在静息状态下的功能图像，探索了具有负边的功能脑网络的拓扑结构及其在精神分裂症中的可能改变。为了最大限度地减少人为负相关的插入，对图像进行了 CompCorr 处理，结果与全局信号回归（GSR）过程进行了比较。使用度分布、中心性、效率和富俱乐部行为来描述具有负连接的健康对照组与精神分裂症患者的功能脑网络。结果表明，具有正、负值的功能脑网络具有截断幂律度分布。此外，尽管功能脑网络具有负数值，但没有小世界拓扑结构，但它们显示出特定的非聚类配置：连接越多的节点之间的连接越少。使用 GSR 过程会丢失此特征。最后，与精神分裂症患者的比较显示与中央节点之间连接减少相关的局部和全局效率降低。总之，尽管具有负数值的功能脑网络缺乏明确的拓扑结构，但具有与随机不同的特定特征，并表明与精神分裂症相关的改变的相关性。
