Weaver Kurt E, Wander Jeremiah D, Ko Andrew L, Casimo Kaitlyn, Grabowski Thomas J, Ojemann Jeffrey G, Darvas Felix
University of Washington, Department of Radiology, USA; University of Washington, Graduate Program in Neuroscience, USA; University of Washington, Integrated Brain Imaging Center, USA.
University of Washington, Department of Bioengineering, USA.
Neuroimage. 2016 Mar;128:238-251. doi: 10.1016/j.neuroimage.2015.12.043. Epub 2015 Dec 30.
Functional imaging investigations into the brain's resting state interactions have yielded a wealth of insight into the intrinsic and dynamic neural architecture supporting cognition and behavior. Electrophysiological studies however have highlighted the fact that synchrony across large-scale cortical systems is composed of spontaneous interactions occurring at timescales beyond the traditional resolution of fMRI, a feature that limits the capacity of fMRI to draw inference on the true directional relationship between network nodes. To approach the question of directionality in resting state signals, we recorded resting state functional MRI (rsfMRI) and electrocorticography (ECoG) from four human subjects undergoing invasive epilepsy monitoring. Using a seed-point based approach, we employed phase-amplitude coupling (PAC) and biPhase Locking Values (bPLV), two measures of cross-frequency coupling (CFC) to explore both outgoing and incoming connections between the seed and all non-seed, site electrodes. We observed robust PAC between a wide range of low-frequency phase and high frequency amplitude estimates. However, significant bPLV, a CFC measure of phase-phase synchrony, was only observed at specific narrow low and high frequency bandwidths. Furthermore, the spatial patterns of outgoing PAC connectivity were most closely associated with the rsfMRI connectivity maps. Our results support the hypothesis that PAC is relatively ubiquitous phenomenon serving as a mechanism for coordinating high-frequency amplitudes across distant neuronal assemblies even in absence of overt task structure. Additionally, we demonstrate that the spatial distribution of a seed-point rsfMRI sensorimotor network is strikingly similar to specific patterns of directional PAC. Specifically, the high frequency activities of distal patches of cortex owning membership in a rsfMRI sensorimotor network were most likely to be entrained to the phase of a low frequency rhythm engendered from the neural populations at the seed-point, suggestive of greater directional coupling from the seed out to the site electrodes.
对大脑静息状态交互作用的功能成像研究，已经在支持认知和行为的内在动态神经结构方面产生了丰富的见解。然而，电生理学研究强调了这样一个事实，即大规模皮层系统中的同步性是由发生在功能性磁共振成像（fMRI）传统分辨率之外的时间尺度上的自发交互作用组成的，这一特征限制了fMRI推断网络节点之间真正方向关系的能力。为了解决静息状态信号中的方向性问题，我们记录了四名接受侵入性癫痫监测的人类受试者的静息状态功能磁共振成像（rsfMRI）和皮层脑电图（ECoG）。我们采用基于种子点的方法，运用相位-振幅耦合（PAC）和双相位锁定值（bPLV）这两种交叉频率耦合（CFC）测量方法，来探索种子点与所有非种子点部位电极之间的传出和传入连接。我们观察到在广泛的低频相位和高频振幅估计之间存在强大的PAC。然而，显著的bPLV（一种相位-相位同步的CFC测量方法）仅在特定的狭窄低频和高频带宽处被观察到。此外，传出PAC连接的空间模式与rsfMRI连接图谱最为密切相关。我们的结果支持这样一种假设，即PAC是一种相对普遍的现象，即使在没有明显任务结构的情况下，它也是协调远距离神经元集合之间高频振幅的一种机制。此外，我们证明了种子点rsfMRI感觉运动网络的空间分布与特定的方向性PAC模式惊人地相似。具体而言，属于rsfMRI感觉运动网络的皮层远端区域的高频活动最有可能被种子点神经群体产生的低频节律的相位所夹带，这表明从种子点到部位电极存在更大的方向耦合。
