Sun Felice T, Miller Lee M, D'Esposito Mark
Helen Wills Neuroscience Institute, University of California, Berkeley, 94720, USA.
Neuroimage. 2005 Oct 15;28(1):227-37. doi: 10.1016/j.neuroimage.2005.05.043. Epub 2005 Jul 12.
We present a novel method to measure relative latencies between functionally connected regions using phase-delay of functional magnetic resonance imaging data. Derived from the phase component of coherency, this quantity estimates the linear delay between two time-series. In conjunction with coherence, derived from the magnitude component of coherency, phase-delay can be used to examine the temporal properties of functional networks. In this paper, we apply coherence and phase-delay methods to fMRI data in order to investigate dynamics of the motor network during task and rest periods. Using the supplementary motor area (SMA) as a reference region, we calculated relative latencies between the SMA and other regions within the motor network including the dorsal premotor cortex (PMd), primary motor cortex (M1), and posterior parietal cortex (PPC). During both the task and rest periods, we measured significant delays that were consistent across subjects. Specifically, we found significant delays between the SMA and the bilateral PMd, bilateral M1, and bilateral PPC during the task condition. During the rest condition, we found that the temporal dynamics of the network changed relative to the task period. No significant delays were measured between the SMA and the left PM and left M1; however, the right PM, right M1, and bilateral PPC were significantly delayed with respect to the SMA. Additionally, we observed significant map-wise differences in the dynamics of the network at task compared to the network at rest. These differences were observed in the interaction between the SMA and the left M1, left superior frontal gyrus, and left middle frontal gyrus. These temporal measurements are important in determining how regions within a network interact and provide valuable information about the sequence of cognitive processes within a network.
我们提出了一种使用功能磁共振成像数据的相位延迟来测量功能连接区域之间相对延迟的新方法。该量从相干性的相位分量导出，估计两个时间序列之间的线性延迟。结合从相干性的幅度分量导出的相干性，相位延迟可用于检查功能网络的时间特性。在本文中，我们将相干性和相位延迟方法应用于功能磁共振成像数据，以研究任务期和休息期运动网络的动态变化。以辅助运动区（SMA）作为参考区域，我们计算了SMA与运动网络内其他区域之间的相对延迟，这些区域包括背侧运动前皮层（PMd）、初级运动皮层（M1）和顶叶后皮层（PPC）。在任务期和休息期，我们测量到了受试者间一致的显著延迟。具体而言，我们发现在任务状态下，SMA与双侧PMd、双侧M1和双侧PPC之间存在显著延迟。在休息状态下，我们发现网络的时间动态相对于任务期发生了变化。在SMA与左侧PMd和左侧M1之间未测量到显著延迟；然而，右侧PMd、右侧M1和双侧PPC相对于SMA有显著延迟。此外，我们观察到任务时网络动态与休息时网络动态在图谱上存在显著差异。这些差异在SMA与左侧M1、左侧额上回和左侧额中回之间的相互作用中观察到。这些时间测量对于确定网络内区域如何相互作用以及提供有关网络内认知过程序列的有价值信息非常重要。
