Salvador Raymond, Suckling John, Schwarzbauer Christian, Bullmore Ed
Brain Mapping Unit and Wolfson Brain Imaging Centre, Department of Psychiatry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QQ, UK.
Philos Trans R Soc Lond B Biol Sci. 2005 May 29;360(1457):937-46. doi: 10.1098/rstb.2005.1645.
We explored properties of whole brain networks based on multivariate spectral analysis of human functional magnetic resonance imaging (fMRI) time-series measured in 90 cortical and subcortical subregions in each of five healthy volunteers studied in the (no-task) resting state. We note that undirected graphs representing conditional independence between multivariate time-series can be more readily approached in the frequency domain than the time domain. Estimators of partial coherency and normalized partial mutual information phi, an integrated measure of partial coherence over an arbitrary frequency band, are applied. Using these tools, we replicate the prior observations that bilaterally homologous brain regions tend to be strongly connected and functional connectivity is generally greater at low frequencies [0.0004, 0.1518 Hz]. We also show that long-distance intrahemispheric connections between regions of prefrontal and parietal cortex were more salient at low frequencies than at frequencies greater than 0.3 Hz, whereas many local or short-distance connections, such as those comprising segregated dorsal and ventral paths in posterior cortex, were also represented in the graph of high-frequency connectivity. We conclude that the partial coherency spectrum between a pair of human brain regional fMRI time-series depends on the anatomical distance between regions: long-distance (greater than 7 cm) edges represent conditional dependence between bilaterally symmetric neocortical regions, and between regions of prefrontal and parietal association cortex in the same hemisphere, are predominantly subtended by low-frequency components.
我们基于对五名健康志愿者在（无任务）静息状态下于90个皮质和皮质下亚区域测量的人类功能磁共振成像（fMRI）时间序列进行多变量频谱分析，探索了全脑网络的特性。我们注意到，在频域中比在时域中更容易处理表示多变量时间序列之间条件独立性的无向图。应用了偏相干性估计器和归一化偏互信息phi，phi是在任意频带上的偏相干性综合度量。使用这些工具，我们重复了先前的观察结果，即双侧同源脑区往往紧密相连，并且在低频[0.0004, 0.1518 Hz]时功能连接性通常更强。我们还表明，前额叶和顶叶皮质区域之间的长距离半球内连接在低频时比在高于0.3 Hz的频率时更显著，而许多局部或短距离连接，例如后皮质中包括分离的背侧和腹侧路径的连接，也在高频连接图中有所体现。我们得出结论，一对人类脑区fMRI时间序列之间的偏相干性频谱取决于区域之间的解剖距离：长距离（大于7厘米）的边表示双侧对称新皮质区域之间以及同一半球内前额叶和顶叶联合皮质区域之间的条件依赖性，主要由低频成分支撑。
