Globally coherent patterns of phase can be obscured by analysis techniques that aggregate brain activity measures across-trials, whether prior to source localization or for estimating inter-areal coherence. We analyzed, at single-trial level, whole head MEG recorded during an observer-triggered apparent motion task. Episodes of globally coherent activity occurred in the delta, theta, alpha and beta bands of the signal in the form of large-scale waves, which propagated with a variety of velocities. Their mean speed at each frequency band was proportional to temporal frequency, giving a range of 0.06 to 4.0 m/s, from delta to beta. The wave peaks moved over the entire measurement array, during both ongoing activity and task-relevant intervals; direction of motion was more predictable during the latter. A large proportion of the cortical signal, measurable at the scalp, exists as large-scale coherent motion. We argue that the distribution of observable phase velocities in MEG is dominated by spatial filtering considerations in combination with group velocity of cortical activity. Traveling waves may index processes involved in global coordination of cortical activity.
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机译：可以通过汇总跨试验的大脑活动度量的分析技术来掩盖全局一致的阶段模式，无论是在进行源定位之前还是为了估计区域间的一致性。我们在一次试验中分析了观察者触发的明显运动任务期间记录的整个头部MEG。全球相干活动的发作以大范围波的形式出现在信号的δ，θ，α和β带中，并以各种速度传播。它们在每个频带的平均速度与时间频率成正比，从delta到beta，范围为0.06到4.0 m / s。在持续的活动和与任务相关的时间间隔内，波峰在整个测量阵列中移动；在后者期间，运动方向更容易预测。皮层信号的大部分（在头皮处可测量）以大规模相干运动的形式存在。我们认为，MEG中可观察到的相速度的分布主要受空间滤波考虑因素和皮层活动群速度的影响。行波可以索引参与皮层活动全球协调的过程。
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