BACKGROUND & AIMS: :Regarding the evoked potential (EP) as a superposition of evoked EEG rhythms in several frequency ranges, we investigated the following issue: Are distinct evoked rhythms, in particular the alpha (8-15 Hz) response, related to separable physiological processes? Frequency domain analysis of EPs was used to evaluate results of cross-modality experiments, i.e.: responses to auditory stimuli were simultaneously recorded from the auditory cortex (adequate stimulation) and from the visual cortex (inadequate stimulation). Responses to visual stimuli were recorded from the same sites. The results of these experiments and further measurements (EEG and MEG responses in humans, among them multiple sclerosis patients) are consistent in the following respect: The amplitudes of alpha responses are dependent on whether or not a stimulus applied is adequate. Alpha responses may thus be related mostly to primary sensory processing. In contrast, theta responses (4-7 Hz) were observed for adequate as well as inadequate stimuli. They may be related rather to associative and cognitive processing than to primary sensory processing. Thus frequency responses, in particular the alpha response, are not artificial results of digital filtering, but functionally significant brain responses.

背景与目标： : 关于诱发电位 (EP) 作为诱发EEG节律在几个频率范围内的叠加，我们研究了以下问题: 不同的诱发节律，特别是 α (8-15Hz) 响应是否与可分离的生理过程有关？EPs的频域分析用于评估交叉模式实验的结果，即: 同时从听觉皮层 (适当的刺激) 和视觉皮层 (不充分的刺激) 记录对听觉刺激的反应。从相同的部位记录对视觉刺激的反应。这些实验和进一步测量的结果 (人类的EEG和MEG反应，其中包括多发性硬化症患者) 在以下方面是一致的: α 反应的幅度取决于所施加的刺激是否足够。因此，Alpha反应可能主要与初级感觉处理有关。相反，对于足够和不充分的刺激，观察到theta反应 (4-7Hz)。它们可能与联想和认知加工有关，而不是与主要的感觉加工有关。因此，频率响应 (尤其是alpha响应) 不是数字滤波的人工结果，而是功能上重要的大脑响应。

BACKGROUND & AIMS: :This paper proposes a novel prewhitening eigenspace beamformer suitable for magnetoencephalogram (MEG) source reconstruction when large background brain activities exist. The prerequisite for the method is that control-state measurements, which contain only the contributions from the background interference, be available, and that the covariance matrix of the background interference can be obtained from such control-state measurements. The proposed method then uses this interference covariance matrix to remove the influence of the interference in the reconstruction obtained from the target measurements. A numerical example, as well as applications to two types of MEG data, demonstrates the effectiveness of the proposed method.

背景与目标： : 本文提出了一种新型的预白化特征空间波束形成器，适用于存在大背景脑活动时的脑磁图 (MEG) 源重建。该方法的先决条件是仅包含来自背景干扰的贡献的控制状态测量是可用的，并且可以从这种控制状态测量中获得背景干扰的协方差矩阵。然后，所提出的方法使用此干扰协方差矩阵来消除从目标测量获得的重建中的干扰的影响。一个数值示例以及在两种类型的MEG数据中的应用证明了该方法的有效性。

BACKGROUND & AIMS: :During rest, envelopes of band-limited on-going MEG signals co-vary across the brain in consistent patterns, which have been related to resting-state networks measured with fMRI. To investigate the genesis of such envelope correlations, we consider a whole-brain network model assuming two distinct fundamental scenarios: one where each brain area generates oscillations in a single frequency, and a novel one where each brain area can generate oscillations in multiple frequency bands. The models share, as a common generator of damped oscillations, the normal form of a supercritical Hopf bifurcation operating at the critical border between the steady state and the oscillatory regime. The envelopes of the simulated signals are compared with empirical MEG data using new methods to analyse the envelope dynamics in terms of their phase coherence and stability across the spectrum of carrier frequencies. Considering the whole-brain model with a single frequency generator in each brain area, we obtain the best fit with the empirical MEG data when the fundamental frequency is tuned at 12Hz. However, when multiple frequency generators are placed at each local brain area, we obtain an improved fit of the spatio-temporal structure of on-going MEG data across all frequency bands. Our results indicate that the brain is likely to operate on multiple frequency channels during rest, introducing a novel dimension for future models of large-scale brain activity.

背景与目标： : 在休息期间，带受限的持续MEG信号的包络以一致的模式在整个大脑中共同变化，这与用fMRI测量的静息状态网络有关。为了研究这种包络相关性的起源，我们考虑了一个全脑网络模型，假设有两种不同的基本情况: 一种是每个大脑区域在单个频率中产生振荡，而一种是每个大脑区域可以在多个频率中产生振荡的新颖频带。作为阻尼振荡的常见生成器，这些模型共享在稳态和振荡状态之间的临界边界处运行的超临界Hopf分叉的正常形式。使用新方法将模拟信号的包络与经验MEG数据进行比较，以根据其在载波频谱上的相位相干性和稳定性来分析包络动力学。考虑到在每个大脑区域具有单个频率发生器的全脑模型，当基频调谐到12Hz时，我们获得了与经验MEG数据的最佳拟合。但是，当在每个局部大脑区域放置多个频率发生器时，我们获得了对所有频带上正在进行的MEG数据的时空结构的改进拟合。我们的结果表明，大脑在休息期间可能会在多个频率通道上运行，从而为未来的大规模大脑活动模型引入了新的维度。

BACKGROUND & AIMS: :A method for the modeling of human movement-related cortical activity from combined electroencephalography (EEG) and magnetoencephalography (MEG) data is proposed. This method includes a subject's multi-compartment head model (scalp, skull, dura mater, cortex) constructed from magnetic resonance images, multi-dipole source model, and a regularized linear inverse source estimate based on boundary element mathematics. Linear inverse source estimates of cortical activity were regularized by taking into account the covariance of background EG and MEG sensor noise. EEG (121 sensors) and MEG (43 sensors) data were recorded in separate sessions whereas normal subjects executed voluntary right one-digit movements. Linear inverse source solution of EEG, MEG, and EEG-MEG data were quantitatively evaluated by using three performance indexes. The first two indexes (Dipole Localization Error [DLE] and Spatial Dispersion [SDis]) were used to compute the localization power for the source solutions obtained. Such indexes were based on the information provided by the column of the resolution matrix (i.e., impulse response). Ideal DLE values tend to zero (the source current was correctly retrieved by the procedure). In contrast, high DLE values suggest severe mislocalization in the source reconstruction. A high value of SDis at a source space point mean that such a source will be retrieved by a large area with the linear inverse source estimation. The remaining performance index assessed the quality of the source solution based on the information provided by the rows of the resolution matrix R, i.e., resolution kernels. The i-th resolution kernels of the matrix R describe how the estimation of the i-th source is distorted by the concomitant activity of all other sources. A statistically significant lower dipole localization error was observed and lower spatial dispersion in source solutions produced by combined EEG-MEG data than from EEG and MEG data considered separately (P < 0.05). These effects were not due to an increased number of sensors in the combined EEG-MEG solutions. They result from the independence of source information conveyed by the multimodal measurements. From a physiological point of view, the linear inverse source solution of EEG-MEG data suggested a contralaterally preponderant bilateral activation of primary sensorimotor cortex from the preparation to the execution of the movement. This activation was associated with that of the supplementary motor area. The activation of bilateral primary sensorimotor cortical areas was greater during the processing of afferent information related to the ongoing movement than in the preparation for the motor act. In conclusion, the linear inverse source estimate of combined MEG and EEG data improves the estimate of movement-related cortical activity.

背景与目标： : 提出了一种根据脑电图 (EEG) 和脑磁图 (MEG) 数据对人体运动相关皮质活动进行建模的方法。该方法包括由磁共振图像构建的受试者的多隔室头部模型 (头皮，头骨，硬脑膜，皮质)，多偶极子源模型以及基于边界元数学的正则化线性逆源估计。通过考虑背景EG和MEG传感器噪声的协方差，对皮质活动的线性逆源估计进行了正则化。EEG (121传感器) 和MEG (43传感器) 数据在单独的会话中记录，而正常受试者执行自愿的右一位运动。通过使用三个性能指标定量评估EEG，MEG和eeg-meg数据的线性逆源解。前两个指标 (偶极定位误差 [DLE] 和空间色散 [SDis]) 用于计算获得的源解的定位能力。此类索引基于分辨率矩阵列提供的信息 (即冲动响应)。理想的DLE值趋于零 (通过该过程正确检索了源电流)。相反，较高的DLE值表明源重建过程中存在严重的错误定位。在源空间点处的高SDis值意味着该源将通过线性逆源估计被大面积检索。剩余性能指标根据解析矩阵R的行 (即解析内核) 提供的信息评估源解决方案的质量。矩阵R的第i个分辨率内核描述了第i个源的估计如何因所有其他源的伴随活动而失真。与单独考虑的EEG和MEG数据相比，在由组合eeg-meg数据产生的源溶液中，观察到具有统计学意义的较低偶极子定位误差和较低的空间色散 (P <0.05)。这些影响不是由于组合eeg-meg溶液中传感器数量的增加所致。它们是由多模式测量所传达的源信息的独立性引起的。从生理学的角度来看，eeg-meg数据的线性逆源解决方案表明，从准备到执行运动，主要感觉运动皮层的双向激活对侧优势。这种激活与补充运动区的激活有关。在处理与正在进行的运动有关的传入信息时，双侧初级感觉运动皮层区域的激活要比准备运动动作时更大。总之，结合MEG和EEG数据的线性逆源估计改善了与运动相关的皮层活动的估计。

BACKGROUND & AIMS: :Source modelling in magnetoencephalography (MEG) requires precise co-registration of the sensor array and the anatomical structure of the measured individual's head. In conventional MEG, the positions and orientations of the sensors relative to each other are fixed and known beforehand, requiring only localization of the head relative to the sensor array. Since the sensors in on-scalp MEG are positioned on the scalp, locations of the individual sensors depend on the subject's head shape and size. The positions and orientations of on-scalp sensors must therefore be measured at every recording. This can be achieved by inverting conventional head localization, localizing the sensors relative to the head - rather than the other way around. In this study we present a practical method for localizing sensors using magnetic dipole-like coils attached to the subject's head. We implement and evaluate the method in a set of on-scalp MEG recordings using a 7-channel on-scalp MEG system based on high critical temperature superconducting quantum interference devices (high-Tc SQUIDs). The method allows individually localizing the sensor positions, orientations, and responsivities with high accuracy using only a short averaging time (≤ 2 ​mm, < 3° and < 3%, respectively, with 1-s averaging), enabling continuous sensor localization. Calibrating and jointly localizing the sensor array can further improve the accuracy of position and orientation (< 1 ​mm and < 1°, respectively, with 1-s coil recordings). We demonstrate source localization of on-scalp recorded somatosensory evoked activity based on co-registration with our method. Equivalent current dipole fits of the evoked responses corresponded well (within 4.2 ​mm) with those based on a commercial, whole-head MEG system.

背景与目标： : 脑磁图 (MEG) 中的源建模需要对传感器阵列和被测个体头部的解剖结构进行精确的配准。在传统的MEG中，传感器相对于彼此的位置和取向是固定的并且预先知道的，仅需要将头部相对于传感器阵列定位。由于头皮上的MEG中的传感器位于头皮上，因此各个传感器的位置取决于对象的头部形状和大小。因此，必须在每次记录时测量头皮上传感器的位置和方向。这可以通过反转传统的头部定位来实现，从而相对于头部定位传感器，而不是相反。在这项研究中，我们提出了一种实用的方法，该方法使用附着在受试者头部的类偶极子线圈来定位传感器。我们使用基于高临界温度超导量子干涉设备 (高Tc SQUIDs) 的7通道头皮上MEG系统在一组头皮上MEG记录中实施和评估该方法。该方法允许仅使用短平均时间 (分别 ≤ 2毫米、 <3 ° 和 <3%，具有1-s平均) 以高精度单独地定位传感器位置、取向和响应性，从而实现连续的传感器定位。校准和联合定位传感器阵列可以进一步提高位置和方向的精度 (分别为 <1毫米和 <1 °，具有1-s线圈记录)。我们基于与我们的方法的共同配准，证明了头皮上记录的体感诱发活动的源定位。诱发响应的等效电流偶极子拟合与基于商业全头MEG系统的等效电流偶极子拟合非常一致 (在4.2毫米内)。

BACKGROUND & AIMS: :Crossmodal associations form a fundamental aspect of our daily lives. In this study we investigated the neural correlates of crossmodal association in early sensory cortices using magnetoencephalography (MEG). We used a paired associate recognition paradigm in which subjects were tested after multiple training sessions over a span of four weeks. Subjects had to learn 12 abstract, nonlinguistic, pairs of auditory and visual objects that consisted of crossmodal (visual-auditory, VA; auditory-visual, AV) and unimodal (visual-visual, VV; auditory-auditory, AA) paired items. Visual objects included abstract, non-nameable, fractal-like images, and auditory objects included abstract tone sequences. During scanning, subjects were shown the first item of a pair (S1), followed by a delay, then the simultaneous presentation of a visual and auditory stimulus (S2). Subjects were instructed to indicate whether either of the S2 stimuli contained the correct paired associate of S1. Synthetic aperture magnetometry (SAMspm), a minimum variance beamformer, was then used to assess source power differences between the crossmodal conditions and their corresponding unimodal conditions (i.e., AV-AA and VA-VV) in the beta (15-30 Hz) and low gamma frequencies (31-54 Hz) during the S1 period. We found greater power during S1 in the corresponding modality-specific association areas for crossmodal compared with unimodal stimuli. Thus, even in the absence of explicit sensory input, the retrieval of well-learned, crossmodal pairs activate sensory areas associated with the corresponding modality. These findings support theories which posit that modality-specific regions of cortex are involved in the storage and retrieval of sensory-specific items from long-term memory.

背景与目标： : 跨模联想构成了我们日常生活的一个基本方面。在这项研究中，我们使用脑磁图 (MEG) 研究了早期感觉皮层中跨足结合的神经相关性。我们使用了配对的关联识别范例，在该范例中，受试者在四个星期的多次训练后进行了测试。受试者必须学习12对抽象的，非语言的，对的听觉和视觉对象，这些对象由交叉 (视觉-听觉，VA; 听觉-视觉，AV) 和单峰 (视觉-视觉，VV; 听觉-听觉，AA) 组成配对项目。视觉对象包括抽象的，不可命名的，类似分形的图像，听觉对象包括抽象的音调序列。在扫描过程中，向受试者显示一对中的第一项 (S1)，然后是延迟，然后是视觉和听觉刺激的同时呈现 (S2)。指示受试者指示S2刺激中的任何一个是否包含s1的正确配对关联。然后使用最小方差波束形成器合成孔径磁力计 (SAMspm) 来评估跨模条件与其相应的单峰条件 (即，av-aa和va-vv) 在S1期间的 β (15-30Hz) 和低伽马频率 (31-54Hz)。与单峰刺激相比，我们在S1期间在相应的模态特定关联区域中发现了更大的力量。因此，即使在没有明确的感觉输入的情况下，学习良好的交叉对的检索也会激活与相应模态相关的感觉区域。这些发现支持理论，这些理论认为皮质的形态特定区域参与了长期记忆中感觉特定项目的存储和检索。

BACKGROUND & AIMS: :Modulation of the ~20-Hz brain rhythm has been used to evaluate the functional state of the sensorimotor cortex both in healthy subjects and patients, such as stroke patients. The ~20-Hz brain rhythm can be detected by both magnetoencephalography (MEG) and electroencephalography (EEG), but the comparability of these methods has not been evaluated. Here, we compare these two methods in the evaluating of ~20-Hz activity modulation to somatosensory stimuli. Rhythmic ~20-Hz activity during separate tactile and proprioceptive stimulation of the right and left index finger was recorded simultaneously with MEG and EEG in twenty-four healthy participants. Both tactile and proprioceptive stimulus produced a clear suppression at 300-350 ​ms followed by a subsequent rebound at 700-900 ​ms after stimulus onset, detected at similar latencies both with MEG and EEG. The relative amplitudes of suppression and rebound correlated strongly between MEG and EEG recordings. However, the relative strength of suppression and rebound in the contralateral hemisphere (with respect to the stimulated hand) was significantly stronger in MEG than in EEG recordings. Our results indicate that MEG recordings produced signals with higher signal-to-noise ratio than EEG, favoring MEG as an optimal tool for studies evaluating sensorimotor cortical functions. However, the strong correlation between MEG and EEG results encourages the use of EEG when translating studies to clinical practice. The clear advantage of EEG is the availability of the method in hospitals and bed-side measurements at the acute phase.

背景与目标： : 〜20hz脑节律的调节已用于评估健康受试者和患者 (例如中风患者) 的感觉运动皮层的功能状态。可以通过脑磁图 (MEG) 和脑电图 (EEG) 检测〜20 hz的脑节律，但是尚未评估这些方法的可比性。在这里，我们比较了这两种方法来评估〜20hz活动调制对体感刺激的影响。在24名健康参与者中，与MEG和EEG同时记录了左右食指分别进行触觉和本体感受刺激期间的节律性〜20hz活动。触觉和本体感受刺激在300-350毫秒产生明显的抑制，随后在刺激开始后700-900毫秒产生反弹，在MEG和EEG的相似潜伏期检测到。抑制和反弹的相对幅度在MEG和EEG记录之间密切相关。然而，在MEG中，对侧半球 (相对于受刺激的手) 的抑制和反弹的相对强度明显强于EEG记录。我们的结果表明，MEG记录产生的信号比EEG具有更高的信噪比，这有利于MEG作为评估感觉运动皮层功能的研究的最佳工具。然而，MEG和EEG结果之间的强相关性鼓励在将研究转化为临床实践时使用EEG。EEG的明显优势是该方法在医院中的可用性以及急性期的床侧测量。

BACKGROUND & AIMS: :Magnetoencephalography (MEG) provides millisecond-scale temporal resolution for noninvasive mapping of human brain functions, but the problem of reconstructing the underlying source currents from the extracranial data has no unique solution. Several distributed source estimation methods based on different prior assumptions have been suggested for the resolution of this inverse problem. Recently, a hierarchical Bayesian generalization of the traditional minimum norm estimate (MNE) was proposed, in which the variance of distributed current at each cortical location is considered as a random variable and estimated from the data using the variational Bayesian (VB) framework. Here, we introduce an alternative scheme for performing Bayesian inference in the context of this hierarchical model by using Markov chain Monte Carlo (MCMC) strategies. In principle, the MCMC method is capable of numerically representing the true posterior distribution of the currents whereas the VB approach is inherently approximative. We point out some potential problems related to hyperprior selection in the previous work and study some possible solutions. A hyperprior sensitivity analysis is then performed, and the structure of the posterior distribution as revealed by the MCMC method is investigated. We show that the structure of the true posterior is rather complex with multiple modes corresponding to different possible solutions to the source reconstruction problem. We compare the results from the VB algorithm to those obtained from the MCMC simulation under different hyperparameter settings. The difficulties in using a unimodal variational distribution as a proxy for a truly multimodal distribution are also discussed. Simulated MEG data with realistic sensor and source geometries are used in performing the analyses.

背景与目标： : 脑磁图 (MEG) 为人脑功能的非侵入性映射提供了毫秒级的时间分辨率，但是从颅外数据重建潜在的源电流的问题没有唯一的解决方案。为了解决此逆问题，已经提出了几种基于不同先验假设的分布式源估计方法。最近，提出了传统最小范数估计 (MNE) 的分层贝叶斯泛化，其中将每个皮质位置处的分布电流的方差视为随机变量，并使用变分贝叶斯 (VB) 框架从数据中进行估计。在这里，我们介绍了一种替代方案，用于通过使用马尔可夫链蒙特卡洛 (MCMC) 策略在此层次模型的背景下执行贝叶斯推理。原则上，MCMC方法能够数值表示电流的真实后验分布，而VB方法本质上是近似的。我们指出了先前工作中与超先验选择有关的一些潜在问题，并研究了一些可能的解决方案。然后进行超先验敏感性分析，并研究通过MCMC方法揭示的后验分布的结构。我们证明，真实后验的结构相当复杂，具有多种模式，对应于源重建问题的不同可能解决方案。我们将VB算法的结果与在不同超参数设置下从MCMC仿真中获得的结果进行了比较。还讨论了使用单峰变分分布作为真正的多峰分布的代理的困难。使用具有真实传感器和源几何形状的模拟MEG数据进行分析。

BACKGROUND & AIMS: :Oscillatory brain activity in the alpha band (8-13 Hz) is modulated by cognitive events. Such modulation is reflected in a decrease of alpha (event-related desynchronization; ERD) with high cognitive load, or an increase (event-related synchronization) with low cognitive demand or with active inhibition of distractors. We used magnetoencephalography to investigate the pattern of prefrontal and parieto-occipital alpha modulation related to two variants of visual working memory task (delayed matching-to-sample) with and without a distractor. We tested nonmedicated, nondepressed patients suffering obsessive-compulsive disorder (OCD), and pair-matched healthy controls. The level of event-related alpha as a function of time was estimated using the temporal-spectral evolution technique. The results in OCD patients indicated: (1) a lower level of prestimulus (reference) alpha when compared to controls, (2) a task-phase specific reduction in event-related alpha ERD in particular for delayed matching-to-sample task with distractor, (3) no significant correlations between the pattern of modulation in prefrontal and parietal-occipital alpha oscillatory activity. Despite showing an abnormally low alpha modulation, the OCD patients' performance accuracy was normal. The results suggest a relationship of alpha oscillations and the underlying thalamocortical network to etiology of OCD and an involvement of a compensatory mechanism related to effortful inhibition of extrinsic and intrinsic interference.

背景与目标： : α 波段 (8-13Hz) 的脑振荡活动受认知事件的调节。这种调制反映在具有高认知负荷的alpha降低 (事件相关的去同步; ERD)，或具有低认知需求或主动抑制干扰物的增加 (事件相关的同步)。我们使用脑磁图研究了有和没有干扰物的视觉工作记忆任务 (延迟匹配样本) 的两种变体相关的前额叶和顶枕alpha调制模式。我们测试了患有强迫症 (OCD) 的非药物，非抑郁症患者以及配对的健康对照。使用时间光谱演化技术估算事件相关alpha的水平随时间的变化。强迫症患者的结果表明 :( 1) 与对照组相比，刺激前 (参考) α 水平较低，(2) 事件相关的 α ERD的任务阶段特异性降低，特别是对于延迟匹配样本任务与分心器，(3) 前额叶的调节模式与顶叶-枕叶 α 振荡活动之间无显着相关性。尽管显示出异常低的 α 调制，但强迫症患者的表现准确性正常。结果表明，α 振荡和潜在的丘脑皮层网络与OCD的病因之间存在关系，并且参与了与努力抑制外在和内在干扰有关的补偿机制。

BACKGROUND & AIMS: :The pericentral primary sensorimotor cortices generate the "mu rhythm" with a distinct spectral signature exhibiting two peaks, generated predominantly anterior (20 Hz) or posterior (10 Hz) to the central sulcus; it defines a "background" network state upon which somatosensory inputs will impinge. We used the high spatiotemporal resolution of magnetoencephalography to analyze the perturbation dynamics of these cortical rhythms in response to a series of paired electric median nerve stimuli: single trials were sorted off-line according to increasing power of the 10- or 20-Hz rebounds which occurred 300-600 ms after the first stimulus; using subaverages formed from the upper and lower 20% of this distribution, we analyzed somatosensory evoked fields (SEF) and power modifications caused by the second stimulus in the pair. We report three key findings: (1) the power level of rhythm rebounds triggered by the first stimulus predicted the rebound strength after the second stimulus applied 600 ms later; yet, it was uncorrelated across the 2.4-s interval separating subsequent stimulus pairs. (2) Conventional averaging camouflages substantial trial-to-trial variations of rhythm dynamics including, for example, even non-occurrences of rhythm rebounds. (3) For six of the seven subjects, the background rhythm power did not affect any SEF component; for the subject with the strongest rhythms only intracortically generated deflections (peaking after the thalamocortical input component N20m) varied as function of pre-stimulus 10- or 20-Hz power. Thus, the perturbation dynamics of the pericentral mu rhythm exhibits a significant intertrial variance, which becomes effective mainly at a time scale larger than 600 ms.

背景与目标： : 中心周围的初级感觉运动皮层产生 “mu节律”，具有明显的光谱特征，显示出两个峰，这些峰主要在中央沟的前 (20Hz) 或后 (10Hz) 产生; 它定义了一个 “背景” 网络状态，体感输入将在此状态上冲击。我们使用脑磁图的高时空分辨率来分析这些皮层节律对一系列成对的正中神经电刺激的扰动动力学: 根据10或20Hz反弹的功率增加，对单个试验进行离线排序，发生在第一次刺激后300-600毫秒; 使用由该分布的上下20% 形成的子平均值，我们分析了由该对中的第二刺激引起的体感诱发场 (SEF) 和功率修改。我们报告了三个关键发现 :( 1) 由第一个刺激触发的节奏反弹的力量水平预测了第二个刺激后600毫秒后施加的反弹强度; 然而，在分隔随后的刺激对的2.4-s间隔中，它是不相关的。(2) 传统的平均掩盖了节奏动力学的大量试验到试验的变化，例如，甚至不出现节奏反弹。(3) 对于七个受试者中的六个，背景节奏力量不影响任何SEF分量; 对于节奏最强的受试者，仅在室内产生的偏转 (在丘脑皮层输入分量N20m之后达到峰值) 随刺激前10或20Hz功率的变化而变化。因此，中心周围mu节律的扰动动力学表现出明显的试验间方差，这主要在大于600 ms的时间尺度上变得有效。

BACKGROUND & AIMS: :We present the design of a low-cost system for recording galvanic skin conductance responses (SCRs) from humans in a magnetically shielded room (MSR) simultaneously to magnetoencephalography (MEG). Such a system was so far not available to the MEG community. Its availability is of utmost importance for neuroscience, since it will allow the concurrent assessment of the autonomic and central nervous system activity. The overall system design optimizes high signal to noise ratio (SNR) of SCRs and achieves minimal distortion of the MEG signal. Its development was based on a fiber-optic transformer, with voltage to optical transduction inside the MSR and demodulation outside the MSR. The system was calibrated and tested inside the MEG environment by using a 151-channel CTF whole head system (VSM MedTech Ltd.). MEG measurements were recorded simultaneously to SCRs from five healthy participants to test whether the developed system does not generate artifacts in the MEG data. Two measurements were performed for each participant; one without the system in the MSR, and one with the system in the MSR, connected to the participant and in operation. The data were analyzed using the time and frequency domains in separate statistical analysis. No significant differences were observed between the two sessions for any statistic index. Our results show that the system allows high quality simultaneous recordings of SCRs and MEG signals in the MSR, and can therefore be used as routine addendum to neuroscience experiments.

背景与目标： : 我们介绍了一种低成本系统的设计，该系统用于同时记录磁屏蔽室 (MSR) 中人类的皮肤电传导响应 (scr) 到脑磁图 (MEG)。到目前为止，MEG社区还没有这样的系统。它的可用性对于神经科学至关重要，因为它将允许同时评估自主神经和中枢神经系统的活动。整个系统设计优化了scr的高信噪比 (SNR)，并实现了MEG信号的最小失真。它的开发基于光纤变压器，在MSR内部具有电压到光转换，在MSR外部具有解调功能。通过使用151通道CTF整体头系统 (VSM MedTech Ltd.) 在MEG环境内对系统进行了校准和测试。MEG测量值同时记录到来自五个健康参与者的scr中，以测试开发的系统是否不会在MEG数据中生成伪像。对每个参与者进行了两次测量; 一个在MSR中没有系统，一个在MSR中没有系统，连接到参与者并正在运行。在单独的统计分析中使用时域和频域对数据进行分析。对于任何统计指标，两次会议之间均未观察到显着差异。我们的结果表明，该系统可以在MSR中高质量同时记录scr和MEG信号，因此可以用作神经科学实验的常规附录。

BACKGROUND & AIMS: -2

背景与目标： -2

BACKGROUND & AIMS: :Beamformers are applied for estimating spatiotemporal characteristics of neuronal sources underlying measured MEG/EEG signals. Several MEG analysis toolboxes include an implementation of a linearly constrained minimum-variance (LCMV) beamformer. However, differences in implementations and in their results complicate the selection and application of beamformers and may hinder their wider adoption in research and clinical use. Additionally, combinations of different MEG sensor types (such as magnetometers and planar gradiometers) and application of preprocessing methods for interference suppression, such as signal space separation (SSS), can affect the results in different ways for different implementations. So far, a systematic evaluation of the different implementations has not been performed. Here, we compared the localization performance of the LCMV beamformer pipelines in four widely used open-source toolboxes (MNE-Python, FieldTrip, DAiSS (SPM12), and Brainstorm) using datasets both with and without SSS interference suppression. We analyzed MEG data that were i) simulated, ii) recorded from a static and moving phantom, and iii) recorded from a healthy volunteer receiving auditory, visual, and somatosensory stimulation. We also investigated the effects of SSS and the combination of the magnetometer and gradiometer signals. We quantified how localization error and point-spread volume vary with the signal-to-noise ratio (SNR) in all four toolboxes. When applied carefully to MEG data with a typical SNR (3-15 ​dB), all four toolboxes localized the sources reliably; however, they differed in their sensitivity to preprocessing parameters. As expected, localizations were highly unreliable at very low SNR, but we found high localization error also at very high SNRs for the first three toolboxes while Brainstorm showed greater robustness but with lower spatial resolution. We also found that the SNR improvement offered by SSS led to more accurate localization.

背景与目标： : 波束形成器用于估计测量的MEG/EEG信号基础的神经元源的时空特征。几个MEG分析工具箱包括线性约束最小方差 (LCMV) 波束形成器的实现。但是，实施方式及其结果的差异使波束形成器的选择和应用变得复杂，并可能阻碍其在研究和临床使用中的广泛采用。此外，不同MEG传感器类型 (例如磁力计和平面梯度计) 的组合以及用于干扰抑制的预处理方法 (例如信号空间分离 (SSS)) 的应用可以针对不同的实现以不同的方式影响结果。到目前为止，尚未对不同的实现进行系统的评估。在这里，我们使用具有和不具有SSS干扰抑制的数据集，在四个广泛使用的开源工具箱 (MNE-Python，FieldTrip，DAiSS (SPM12) 和Brainstorm) 中比较了LCMV波束形成器管道的本地化性能。我们分析了MEG数据，这些数据是i) 模拟的，ii) 从静态和移动的幻影记录的，以及iii) 从接受听觉，视觉和体感刺激的健康志愿者记录的。我们还研究了SSS的影响以及磁力计和梯度计信号的组合。我们在所有四个工具箱中量化了定位误差和点扩展体积如何随信噪比 (SNR) 变化。当以典型的SNR (3-15 dB) 仔细应用于MEG数据时，所有四个工具箱都可靠地定位了源; 但是，它们对预处理参数的敏感性不同。如预期的那样，在非常低的SNR下定位是非常不可靠的，但是我们发现前三个工具箱在非常高的SNR下定位误差也很高，而Brainstorm显示出更高的鲁棒性，但空间分辨率较低。我们还发现，SSS提供的SNR改进导致了更准确的定位。

BACKGROUND & AIMS: :Magnetoencephalography (MEG) power topography may be useful for obtaining discriminative brain activity patterns that can distinguish depressed patients from healthy control subjects at the individual level. However, the application is still limited due to the lack of adequate analysis strategies to remove artifacts from the MEG signals. In this study, the multichannel matching pursuit (MMP) method was designed; in this technique, a linear decomposition method that provides components by iteratively reanalysing a residual signal after removing previously found components,. Forty-four subjects, half depressed patients and half healthy subjects, were recruited for MEG scanning whilst watching a video of sad faces. MMP was implemented to manage multichannel, multi-trial MEG signals. The representative post-MMP analysis signals were utilised to calculate the power topography over the whole brain and designed as inputs for a Support Vector Machine (SVM) classifier. A statistically significant discriminative accuracy of 86% (p=0.002) after a permutation test was achieved. Comparing the system classification performance to that of the ensemble averaging method and the established Independent Component Analysis (ICA), we demonstrated the ability of MMP to represent critical MEG information and, in turn, to mark the abnormality of oscillatory activities under negative stimuli using images of sad faces.

背景与目标： : 脑磁图 (MEG) 功率地形图可能有助于获得可区分的大脑活动模式，从而在个体水平上区分抑郁症患者与健康对照受试者。但是，由于缺乏足够的分析策略来消除MEG信号中的伪像，因此应用仍然受到限制。在这项研究中，设计了多通道匹配追踪 (MMP) 方法; 在这种技术中，一种线性分解方法，该方法通过在删除先前找到的组件后迭代重新分析残余信号来提供组件。招募了44名受试者 (一半是抑郁症患者，一半是健康受试者) 进行MEG扫描，同时观看了悲伤面孔的视频。实施MMP来管理多通道、多试验的MEG信号。代表性的MMP后分析信号用于计算整个大脑的功率拓扑，并设计为支持向量机 (SVM) 分类器的输入。在置换测试后，86% 的统计学显著判别准确性 (p = 0.002) 被实现。将系统分类性能与集成平均方法和已建立的独立分量分析 (ICA) 进行比较，我们证明了MMP表示关键MEG信息的能力，进而可以使用图像标记负刺激下振荡活动的异常悲伤的面孔。

BACKGROUND & AIMS: :The expression of the different protein kinase C (PKC) isozymes in various states of differentiation of the human megakaryoblastic leukaemia cell line MEG-01 were analysed using thermocycle amplification of mRNA and immunoblotting. MEG-01 expressed mRNAs of PKC alpha, -beta I, -beta II, -delta, -epsilon, -eta, -theta and -zeta, but not PKC gamma. At the protein molecule level, MEG-01 was observed to express PKC alpha, -beta I, -beta II,- epsilon, -theta and -zeta, but lack -gamma, -delta and -eta. When differentiation of MEG-01 was induced by 100 nm 12-O-tetradecanoyl-phorbol-13-acetate (TPA), rapid translocation from cytosol to membrane fraction and down-regulation of PKC alpha, -epsilon and -theta was observed in 1-2h. On the other hand, PKC beta I and -beta II were observed to translocate not only to the membrane fraction but also to the cytoskeletal fraction in a different manner, and their down-regulation, especially beta II, was very slow. The myristoylated, alanine-rich C kinase substrate (MARCKS) in the membrane fraction of MEG-01 cells was observed to decrease gradually throughout the differentiation process. Additionally, time-course study of TPA treatment indicated that incubation of the cells for 30 min is sufficient for differentiation. These results strongly suggest that the activation of PKC alpha, -epsilon and -theta is involved in the initiation of differentiation, and that PKC beta I and -beta II have important roles in the maintenance of differentiation. Although PKC zeta was resistant to TPA treatment and its translocation was reduced, the amount of this isozyme in the cytosol fraction decreased throughout the differentiation process.

背景与目标： : 使用mRNA的热循环扩增和免疫印迹分析了不同蛋白激酶C (PKC) 同工酶在人巨核细胞白血病细胞系MEG-01的各种分化状态中的表达。MEG-01表达PKC α 、-β I、-β II、-δ 、-ε 、-eta、-θ 和-ζ 的mrna，但不表达PKC γ。在蛋白质分子水平上，观察到MEG-01表达PKC α，-β I，-β II，-ε，-θ 和-ζ，但缺少-γ，-δ 和-ζ。当100 nm 12 O-tetradecanoyl-phorbol-13-acetate (TPA) 诱导MEG-01分化时，在1-2小时内观察到从细胞质到膜级分的快速转运以及PKC α，-ε 和-θ 的下调。另一方面，观察到PKC beta I和-beta II不仅以不同的方式易位到膜部分，而且还易位到细胞骨架部分，并且它们的下调，尤其是beta II，非常缓慢。在整个分化过程中，观察到MEG-01细胞膜级分中的肉豆蔻基化，富含丙氨酸的C激酶底物 (MARCKS) 逐渐减少。此外，TPA处理的时程研究表明，将细胞孵育30分钟足以分化。这些结果强烈表明，PKC α，-ε 和-θ 的激活参与了分化的启动，并且PKC β I和-β II在维持分化中起重要作用。尽管PKC zeta对TPA处理具有抗性，并且其易位减少，但在整个分化过程中，胞质溶胶级分中该同工酶的数量减少了。