Young Calvin K, Ruan Ming, McNaughton Neil
Department of Psychology and Brain Health Research Centre, University of Otago, Dunedin, New Zealand.
Wuhan Asia Heart Hospital, Wuhan, China.
Front Syst Neurosci. 2017 Sep 29;11:72. doi: 10.3389/fnsys.2017.00072. eCollection 2017.
Algorithms for estimating directed connectivity have become indispensable to further understand the neurodynamics between functionally coupled brain areas. The evaluation of directed connectivity on the propagation of brain activity has largely been based on simulated data or toy models, where various hidden properties of neurophysiological data may not be fully recapitulated. In this study, directionality was unequivocally manipulated in the freely moving rat in a unique dataset, where normal oscillatory interactions between the supramammillary nucleus (SuM) and hippocampus (HPC) were attenuated by temporary medial septal (MS) inactivation, and replaced by electrical stimulation of the fornix to evaluate the performance of several directed connectivity assessment methods. The directed transfer function, partial directed coherence, directed coherence, pair-wise Geweke-Granger causality, phase slope index, and phase transfer entropy, all found SuM to HPC theta propagation when the MS is inactivated, and HPC activity was driven by peaks of simultaneously recorded SuM theta. As expected from theoretical expectations and simulated data, signal features including coupling strength, signal-to-noise ratio, and stationarity all weakly affected directed connectivity measures. We conclude that all the examined directed connectivity estimates correctly identify artificially imposed uni-directionality of brain oscillations in freely moving animals. Non-auto-regressive modeling based methods appear to be the most robust, and are least affected by inherent features in data such as signal-to-noise ratio and stationarity.
用于估计定向连通性的算法对于进一步理解功能耦合脑区之间的神经动力学已变得不可或缺。对脑活动传播的定向连通性评估很大程度上基于模拟数据或简化模型，而神经生理数据的各种隐藏特性可能无法在其中得到充分体现。在本研究中，在一个独特的数据集中，对自由活动大鼠的方向性进行了明确操控，其中通过暂时内侧隔区（MS）失活减弱了乳头体上核（SuM）与海马体（HPC）之间的正常振荡相互作用，并用穹窿的电刺激取而代之，以评估几种定向连通性评估方法的性能。定向传递函数、偏定向相干性、定向相干性、成对的盖维克 - 格兰杰因果关系、相位斜率指数和相位转移熵，在MS失活时均发现存在从SuM到HPC的θ波传播，且HPC活动由同时记录的SuM θ波峰值驱动。正如理论预期和模拟数据所表明的，包括耦合强度、信噪比和平稳性在内的信号特征对定向连通性测量的影响均较弱。我们得出结论，所有检测的定向连通性估计方法均能正确识别自由活动动物中人为施加的脑振荡单向性。基于非自回归建模的方法似乎最为稳健，且受数据中诸如信噪比和平稳性等固有特征的影响最小。
