Combining EEG and MEG to localize distributed sources of neural activity

描述(由申请人提供)：这个项目的目标是探索性地研究从联合脑磁图/脑电测量中定位神经活动的分布式来源，使用最近开发的逆问题的方法(局部基扩展或LBEX)。 10-100ms时间尺度内的神经动力学是与精神障碍研究相关的广泛认知功能的基础。脑电和脑磁图是唯一具有这种时间分辨率的实用非侵入性技术，但由于传感器测量与潜在来源之间的病态逆问题，其空间分辨率受到限制。EEG的应用更广泛，但也存在头部电导率剖面的不确定性。事实证明，MEG逆问题相对更容易处理。然而，脑磁图的价格要高得多，最好将这两种技术结合起来，这样就可以使用同时的脑磁图测量来更好地精确定位脑电源。将这两种方法结合起来的另一个原因是逆问题的互补性：脑电静音源可以是脑磁图活动的，反之亦然。多亏了最近的乐器进步， 现在通常可以同时测量，但关节定位问题还没有得到充分的研究。我们开发了一种脑磁源定位(LBEX)的方法，通过对控制反问题的不确定原理的数学处理，允许系统地分析分辨率极限。在该方案中，我们建议将LBEX方法扩展到脑电/脑电联合定位。具体目标包括：(1)理想化球形模型中关节定位问题的理论分析；(2)在真实头部模型的数值模拟中评估该技术的性能；(3)将联合定位技术应用于通过实验合作获得的同步脑电/脑电记录。研究项目的成功完成将建立我们的算法框架的实用性，并将评估同时进行脑磁图/脑电定位所获得的收益。一旦该方法通过探索性研究得到验证，我们打算在未来将结果编码到用户友好的软件中，这将使EEG/MEG联合定位得到广泛应用。

DESCRIPTION (provided by applicant): The goal of this project is exploratory research into localization of distributed sources of neural activity from joint MEG/EEG measurements, using a recently developed methodology for the inverse problem (Local Basis Expansions or LBEX). Neural dynamics in the 10-100 ms timescale underlie a broad spectrum of cognitive function relevant to the study of mental disorders. EEG and MEG are the only practical noninvasive techniques with this time resolution, but are limited in spatial resolution due to the ill posed inverse problem relating sensor measurements to underlying sources. EEG is more widely used, but also suffers from uncertainties about head conductivity profiles. The MEG inverse problem has proven to be comparatively more tractable. However, MEG is substantially more expensive, and it is desirable to combine the two techniques, so that EEG sources can be better pinpointed using simultaneous MEG measurements. Another reason to combine the two methods is the complementary nature of the inverse problems: EEG silent sources can be MEG active, and vice versa. Thanks to recent instrumental advances, simultaneous measurements are now routinely possible, but the joint localization problem has not yet been fully studied. We have developed a methodology for MEG source localization (LBEX), which permits a systematic analysis of resolution limits, through a mathematical treatment of the uncertainty principle governing the inverse problem. In this proposal, we propose to explore extensions of the LBEX method to joint MEG/EEG source localization. Specific aims include (i) a theoretical analysis of the joint localization problem in an idealized spherical model, (ii) evaluation of the performance of the technique in numerical simulations with a realistic head model, and (iii) application of the joint localization technique to simultaneous MEG/EEG recordings obtained through an experimental collaboration. Successful completion of the research program will establish the utility of our algorithmic framework, and will also evaluate the gain obtained from simultaneous MEG/EEG localization. Once the methodology is validated by the exploratory research, we intend in the future to encode the results into user friendly software which will enable widespread usage of joint EEG/MEG localization.