Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, 6525 EN Nijmegen, The Netherlands.
Comput Math Methods Med. 2012;2012:451938. doi: 10.1155/2012/451938. Epub 2012 May 10.
The availability of multichannel neuroimaging techniques, such as MEG and EEG, provides us with detailed topographical information of the recorded magnetic and electric signals and therefore gives us a good overview on the concomitant signals generated in the brain. To assess the location and the temporal dynamics of neuronal sources with noninvasive recordings, reconstruction tools such as beamformers have been shown to be useful. In the current study, we are in particular interested in cortical motor control involved in the isometric contraction of finger muscles. To this end we are measuring the interaction between the dynamics of brain signals and the electrical activity of hand muscles. We were interested to find out whether in addition to the well-known correlated activity between contralateral primary motor cortex and the hand muscles, additional functional connections can be demonstrated. We adopted coherence as a functional index and propose a so-called nulling beamformer method which is computationally efficient and addresses the localization of multiple correlated sources. In simulations of cortico-motor coherence, the proposed method was able to correctly localize secondary sources. The application of the approach on real electromyographic and magnetoencephalographic data collected during an isometric contraction and rest revealed an additional activity in the hemisphere ipsilateral to the hand involved in the task.
多通道神经影像学技术（如 MEG 和 EEG）的出现为我们提供了记录的磁场和电场的详细拓扑信息，因此使我们能够很好地了解大脑中同时产生的信号。为了评估非侵入性记录中神经元源的位置和时变动态，波束形成器等重建工具已被证明是有用的。在当前的研究中，我们特别关注涉及手指肌肉等长收缩的皮质运动控制。为此，我们正在测量大脑信号的动力学与手部肌肉的电活动之间的相互作用。我们有兴趣了解除了众所周知的对侧初级运动皮层与手部肌肉之间的相关活动之外，是否还可以证明其他功能连接。我们采用相干性作为功能指标，并提出了一种所谓的“零化波束形成器”方法，该方法计算效率高，并解决了多个相关源的定位问题。在皮质运动相干性的模拟中，所提出的方法能够正确定位次要源。该方法应用于在等长收缩和休息期间采集的真实肌电图和脑磁图数据，揭示了在参与任务的手部对侧半球中存在额外的活动。
