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。

BACKGROUND & AIMS: :A rapidly growing number of neuromagnetic studies focus on the analysis of auditory steady-state responses (ASSR) in relation to a diverse array of factors including age, selective attention, and presence of psychopathology. The objectives of these studies require accurate spatio-temporal estimation of the underlying neural generators, a challenging task due to the relatively low signal strength and high correlation between bilateral auditory cortical sources. This paper evaluates the performance of two beamforming schemes that can potentially overcome such difficulties: 1) the linearly constrained minimum variance beamformer with partial sensor coverage (LCMV-PSC), and 2) the multiple constrained minimum-variance beamformer with coherent source region suppression (MCMV-CSRS). Simulation experiments are conducted to assess the impact of source parameters on the reconstruction accuracy. The results indicate that the LCMV-PSC method is prone to localization errors that essentially occur along medio-lateral directions, increase with source depth, and are associated to amplitude and phase distortions of the estimated time courses of activity. Comparatively, the MCMV-CSRS method exhibits precise localization and minimal amplitude and phase distortion for a broad range of relative interferer's positions within the suppression region. The results from the numerical experiments are validated on real magnetoencephalographic (MEG) data collected from a 40-Hz ASSR paradigm.

背景与目标： : 越来越多的神经磁学研究专注于分析听觉稳态反应 (ASSR) 与各种因素有关，包括年龄，选择性注意和精神病理学的存在。这些研究的目标需要对潜在的神经发生器进行准确的时空估计，这是一项艰巨的任务，因为信号强度相对较低且双边听觉皮层源之间的相关性较高。本文评估了两种可能克服此类困难的波束形成方案的性能: 1) 具有部分传感器覆盖的线性约束最小方差波束形成器 (lcmv-psc)，以及2) 具有相干源区抑制的多重约束最小方差波束形成器 (mcmv-csrs)。进行了仿真实验，以评估源参数对重建精度的影响。结果表明，lcmv-psc方法容易发生定位误差，这些误差基本上沿中横向方向发生，随着源深度的增加而增加，并且与估计的活动时间过程的幅度和相位失真有关。相比之下，MCMV-CSRS方法在抑制区域内的相对干扰源位置范围很广，表现出精确的定位以及最小的幅度和相位失真。数值实验的结果已在从40Hz ASSR范例收集的真实脑磁图 (MEG) 数据上进行了验证。

BACKGROUND & AIMS: :A number of brain imaging techniques have been developed in order to investigate brain function and to develop diagnostic tools for various brain disorders. Each modality has strengths as well as weaknesses compared to the others. Recent work has explored how multiple modalities can be integrated effectively so that they complement one another while maintaining their individual strengths. Bayesian inference employing Markov Chain Monte Carlo (MCMC) techniques provides a straightforward way to combine disparate forms of information while dealing with the uncertainty in each. In this paper we introduce methods of Bayesian inference as a way to integrate different forms of brain imaging data in a probabilistic framework. We formulate Bayesian integration of magnetoencephalography (MEG) data and functional magnetic resonance imaging (fMRI) data by incorporating fMRI data into a spatial prior. The usefulness and feasibility of the method are verified through testing with both simulated and empirical data.

背景与目标： : 已经开发了许多脑成像技术，以研究脑功能并开发针对各种脑部疾病的诊断工具。与其他方式相比，每种方式都有优点和缺点。最近的工作探讨了如何有效地整合多种模式，以便它们在保持各自优势的同时相互补充。采用马尔可夫链蒙特卡洛 (MCMC) 技术的贝叶斯推理提供了一种简单的方法来组合不同形式的信息，同时处理每种信息中的不确定性。在本文中，我们介绍了贝叶斯推理方法，作为在概率框架中集成不同形式的大脑成像数据的一种方法。通过将fMRI数据合并到空间先验中，我们制定了脑磁图 (MEG) 数据和功能磁共振成像 (fMRI) 数据的贝叶斯集成。通过模拟和经验数据的测试，验证了该方法的有效性和可行性。

BACKGROUND & AIMS: :The recent decade has seen a shift from artificial and environmentally deprived experiments in neuroscience to real-life studies on multiple brains in interaction, coordination and synchrony. In these new interpersonal synchrony experiments, there has been a growing trend to employ naturalistic social interactions to evaluate mechanisms underlying synchronous neuronal communication. Here, we emphasize the importance of integrating the assessment of neural synchrony with measurement of nonverbal behavioral synchrony as expressed in various social contexts: relaxed social interactions, planning a joint pleasurable activity, conflict discussion, invocation of trauma, or support giving and assess the integration of neural and behavioral synchrony across developmental stages and psychopathological conditions. We also showcase the advantages of magnetoencephalography neuroimaging as a promising tool for studying interactive neural synchrony and consider the challenge of ecological validity at the expense of experimental rigor. We review recent evidence of rhythmic information flow between brains in interaction and conclude with addressing state-of-the-art developments that may contribute to advance research on brain-to-brain coordination to the next level.

背景与目标： : 最近十年，从神经科学领域的人工和环境剥夺实验转变为对多个大脑在相互作用，协调和同步方面的现实研究。在这些新的人际同步实验中，越来越多的趋势是采用自然社会互动来评估同步神经元交流的机制。在这里，我们强调将神经同步性评估与在各种社会环境中表达的非语言行为同步性测量相结合的重要性: 轻松的社会互动，计划共同的愉悦活动，冲突讨论，创伤的调用，或支持给予和评估跨发育阶段和心理病理条件的神经和行为同步性的整合。我们还展示了脑磁图神经成像作为研究交互式神经同步的有前途的工具的优势，并考虑了以实验严谨性为代价的生态有效性挑战。我们回顾了大脑之间相互作用的节奏信息流的最新证据，并以解决最新的发展作为结论，这些发展可能有助于将脑对脑协调的研究推向新的水平。

BACKGROUND & AIMS: :Abstract We describe a comprehensive linear approach to the problem of imaging brain activity with high temporal as well as spatial resolution based on combining EEG and MEG data with anatomical constraints derived from MRI images. The "inverse problem" of estimating the distribution of dipole strengths over the cortical surface is highly underdetermined, even given closely spaced EEG and MEG recordings. We have obtained much better solutions to this problem by explicitly incorporating both local cortical orientation as well as spatial covariance of sources and sensors into our formulation. An explicit polygonal model of the cortical manifold is first constructed as follows: (1) slice data in three orthogonal planes of section (needle-shaped voxels) are combined with a linear deblurring technique to make a single high-resolution 3-D image (cubic voxels), (2) the image is recursively flood-filled to determine the topology of the gray-white matter border, and (3) the resulting continuous surface is refined by relaxing it against the original 3-D gray-scale image using a deformable template method, which is also used to computationally flatten the cortex for easier viewing. The explicit solution to an error minimization formulation of an optimal inverse linear operator (for a particular cortical manifold, sensor placement, noise and prior source covariance) gives rise to a compact expression that is practically computable for hundreds of sensors and thousands of sources. The inverse solution can then be weighted for a particular (averaged) event using the sensor covariance for that event. Model studies suggest that we may be able to localize multiple cortical sources with spatial resolution as good as PET with this technique, while retaining a much finer grained picture of activity over time.

背景与目标： : 摘要我们描述了一种综合的线性方法，该方法基于将EEG和MEG数据与从MRI图像得出的解剖约束相结合的方法，来解决具有高时间和空间分辨率的脑活动成像问题。即使在紧密间隔的EEG和MEG记录下，估计偶极子强度在皮层表面上的分布的 “反问题” 也被高度低估。通过将局部皮层方向以及源和传感器的空间协方差明确地结合到我们的配方中，我们已经获得了更好的解决方案。首先构造皮质流形的显式多边形模型如下 :( 1) 将三个正交截面平面 (针状体素) 中的切片数据与线性去模糊技术相结合，以制作单个高分辨率3-D图像 (立方体素)，(2) 对图像进行递归泛洪填充，以确定灰白色物质边界的拓扑，并且 (3) 通过使用可变形模板方法将其相对于原始的3-D灰度图像进行松弛来细化所得的连续表面，它还用于计算使皮层变平，以便于查看。最佳逆线性算子 (对于特定的皮质流形，传感器放置，噪声和先验源协方差) 的误差最小化公式的显式解决方案产生了紧凑的表达式，对于数百个传感器和数千个传感器实际上是可计算的源。然后可以使用针对该事件的传感器协方差对特定 (平均) 事件加权逆解。模型研究表明，使用这种技术，我们可能能够以与PET一样好的空间分辨率定位多个皮质源，同时随着时间的推移保留更精细的活动图景。

BACKGROUND & AIMS: :Brain-computer interfaces (BCIs) allow for communicating intentions by mere brain activity, not involving muscles. Thus, BCIs may offer patients who have lost all voluntary muscle control the only possible way to communicate. Many recent studies have demonstrated that BCIs based on electroencephalography (EEG) can allow healthy and severely paralyzed individuals to communicate. While this approach is safe and inexpensive, communication is slow. Magnetoencephalography (MEG) provides signals with higher spatiotemporal resolution than EEG and could thus be used to explore whether these improved signal properties translate into increased BCI communication speed. In this study, we investigated the utility of an MEG-based BCI that uses voluntary amplitude modulation of sensorimotor mu and beta rhythms. To increase the signal-to-noise ratio, we present a simple spatial filtering method that takes the geometric properties of signal propagation in MEG into account, and we present methods that can process artifacts specifically encountered in an MEG-based BCI. Exemplarily, six participants were successfully trained to communicate binary decisions by imagery of limb movements using a feedback paradigm. Participants achieved significant mu rhythm self control within 32 min of feedback training. For a subgroup of three participants, we localized the origin of the amplitude modulated signal to the motor cortex. Our results suggest that an MEG-based BCI is feasible and efficient in terms of user training.

背景与目标： : 脑机接口 (BCIs) 允许仅通过大脑活动来传达意图，而不涉及肌肉。因此，BCIs可能为失去所有自愿肌肉控制的患者提供唯一可能的交流方式。最近的许多研究表明，基于脑电图 (EEG) 的bci可以使健康和严重瘫痪的人进行交流。虽然这种方法既安全又便宜，但通信速度很慢。脑磁图 (MEG) 提供的信号具有比EEG更高的时空分辨率，因此可以用于探索这些改善的信号特性是否转化为提高的BCI通信速度。在这项研究中，我们调查了基于MEG的BCI的效用，该BCI使用感觉运动mu和 β 节律的自愿幅度调制。为了提高信噪比，我们提出了一种简单的空间滤波方法，该方法考虑了MEG中信号传播的几何特性，并且提出了可以处理基于MEG的BCI中特异性遇到的伪像的方法。例如，成功地训练了六名参与者，以使用反馈范例通过肢体运动的图像来传达二元决策。参与者在反馈训练的32分钟内实现了显着的mu节奏自我控制。对于三个参与者的亚组，我们将调幅信号的起源定位到运动皮层。我们的结果表明，基于MEG的BCI在用户培训方面是可行且有效的。

BACKGROUND & AIMS: :Recording fetal magnetoencephalographic (fMEG) signals in-utero is a demanding task due to biological interference, especially maternal and fetal magnetocardiographic (MCG) signals. A method based on orthogonal projection of MCG signal space vectors (OP) was evaluated and compared with independent component analysis (ICA). The evaluation was based on MCG amplitude reduction and signal-to-noise ratio of fetal brain signals using exemplary datasets recorded during ongoing studies related to auditory evoked fields. The results indicate that the OP method is the preferable approach for attenuation of MCG and for preserving the fetal brain signals in fMEG recordings.

背景与目标： : 由于生物干扰，尤其是母体和胎儿的心磁图 (MCG) 信号，在子宫内记录胎儿脑磁图 (fMEG) 信号是一项艰巨的任务。评估了一种基于MCG信号空间向量 (OP) 正交投影的方法，并将其与独立分量分析 (ICA) 进行了比较。评估基于MCG振幅降低和胎儿大脑信号的信噪比，使用正在进行的与听觉诱发场相关的研究中记录的示例性数据集进行评估。结果表明，OP方法是衰减MCG并在fMEG记录中保留胎儿大脑信号的首选方法。

BACKGROUND & AIMS: :Although a nonspecific cephalic sensation, the so-called "cephalic aura," is a common sensory aura, particularly in frontal lobe seizures, but is rarely is the entire sensory seizure event. The unusual presentation of cephalic sensations in isolation representing supplementary motor area (SMA) seizures, which are commonly unaccompanied by ictal electroencephalography (EEG) changes, can easily lead to misdiagnosis of nonepileptic psychogenic seizures. We illustrate the case of a 36-year-old male patient with frontal lobe epilepsy who presented with isolated cephalic auras described as a nonvertiginous sense of head movement without observable clinical signs after his habitual partial motor seizures were controlled with pharmacotherapy. Video/EEG recordings showed no recognizable epileptic discharges time-locked to the onset of the isolated cephalic auras. Ictal magnetoencephalography (MEG) with synthetic aperture magnetometry-kurtosis (SAM(g(2))) analysis demonstrated the SMA onset of the cephalic auras; thus, MEG was essential in differentiating these isolated auras from nonepileptic psychogenic events.

背景与目标： : 尽管一种非特异性的头颅感觉，即所谓的 “头颅先兆”，是一种常见的感觉先兆，特别是在额叶癫痫发作中，但很少是整个感觉发作事件。隔离地代表辅助运动区 (SMA) 癫痫发作的头部感觉异常表现，通常不伴有发作性脑电图 (EEG) 变化，很容易导致对非癫痫性精神病性癫痫发作的误诊。我们说明了一名36岁的男性额叶癫痫患者的病例，该患者出现孤立的头颅前兆，被描述为在通过药物疗法控制其习惯性部分运动性癫痫发作后没有观察到的临床症状。视频/EEG记录显示，没有可识别的癫痫放电时间锁定在孤立的头颅光环的发作上。具有合成孔径磁力计-峰度 (SAM(g(2) 的Ictal脑磁图 (MEG) 分析证明了头颅光环的SMA发作; 因此，MEG对于区分这些孤立的光环与非癫痫性心理事件至关重要。