Department of Neurology & Stroke, And Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
Department of Neurology & Stroke, And Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany; Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland.
Neuroimage. 2020 Jul 1;214:116761. doi: 10.1016/j.neuroimage.2020.116761. Epub 2020 Mar 18.
Instantaneous phase of brain oscillations in electroencephalography (EEG) is a measure of brain state that is relevant to neuronal processing and modulates evoked responses. However, determining phase at the time of a stimulus with standard signal processing methods is not possible due to the stimulus artifact masking the future part of the signal. Here, we quantify the degree to which signal-to-noise ratio and instantaneous amplitude of the signal affect the variance of phase estimation error and the precision with which "ground truth" phase is even defined, using both the variance of equivalent estimators and realistic simulated EEG data with known synthetic phase. Necessary experimental conditions are specified in which pre-stimulus phase estimation is meaningfully possible based on instantaneous amplitude and signal-to-noise ratio of the oscillation of interest. An open source toolbox is made available for causal (using pre-stimulus signal only) phase estimation along with a EEG dataset consisting of recordings from 140 participants and a best practices workflow for algorithm optimization and benchmarking. As an illustration, post-hoc sorting of open-loop transcranial magnetic stimulation (TMS) trials according to pre-stimulus sensorimotor μ-rhythm phase is performed to demonstrate modulation of corticospinal excitability, as indexed by the amplitude of motor evoked potentials.
脑电（EEG）中脑振荡的瞬时相位是一种与神经元处理相关的脑状态度量，可调节诱发反应。然而，由于刺激伪影掩盖了信号的未来部分，使用标准信号处理方法在刺激时确定相位是不可能的。在这里，我们使用等效估计量的方差和具有已知合成相位的现实模拟 EEG 数据，量化了信噪比和信号瞬时幅度对相位估计误差方差以及“真实”相位定义精度的影响程度。指定了必要的实验条件，基于感兴趣的振荡的瞬时幅度和信噪比，可以有意义地进行刺激前相位估计。提供了一个开源工具箱，用于进行因果（仅使用刺激前信号）相位估计，并提供了一个包含 140 名参与者记录的 EEG 数据集和一个用于算法优化和基准测试的最佳实践工作流程。作为说明，根据刺激前感觉运动 μ 节律相位对开环经颅磁刺激（TMS）试验进行事后分类，以证明运动诱发电位幅度作为皮质脊髓兴奋性的指标的调制。
