INSERM U821, Dynamique Cérébrale et Cognition, Lyon, France.
Comput Intell Neurosci. 2007;2007:67613. doi: 10.1155/2007/67613.
We describe a simple and efficient solution to the problem of reconstructing electromagnetic sources into a canonical or standard anatomical space. Its simplicity rests upon incorporating subject-specific anatomy into the forward model in a way that eschews the need for cortical surface extraction. The forward model starts with a canonical cortical mesh, defined in a standard stereotactic space. The mesh is warped, in a nonlinear fashion, to match the subject's anatomy. This warping is the inverse of the transformation derived from spatial normalization of the subject's structural MRI image, using fully automated procedures that have been established for other imaging modalities. Electromagnetic lead fields are computed using the warped mesh, in conjunction with a spherical head model (which does not rely on individual anatomy). The ensuing forward model is inverted using an empirical Bayesian scheme that we have described previously in several publications. Critically, because anatomical information enters the forward model, there is no need to spatially normalize the reconstructed source activity. In other words, each source, comprising the mesh, has a predetermined and unique anatomical attribution within standard stereotactic space. This enables the pooling of data from multiple subjects and the reporting of results in stereotactic coordinates. Furthermore, it allows the graceful fusion of fMRI and MEG data within the same anatomical framework.
我们描述了一种将电磁源重建到规范或标准解剖空间的简单而有效的解决方案。其简单性在于以避免提取皮质表面的方式将特定于主体的解剖结构纳入正向模型中。正向模型从定义在标准立体定向空间中的规范皮质网格开始。网格以非线性方式变形以匹配主体的解剖结构。这种变形是从使用针对其他成像模式建立的全自动程序对主体的结构 MRI 图像进行空间归一化得出的变换的逆。使用变形网格和球形头部模型（不依赖于个体解剖结构）计算电磁导联场。随后使用我们之前在几篇出版物中描述的经验贝叶斯方案对正向模型进行反演。关键是，由于解剖信息输入正向模型，因此无需对重建源活动进行空间归一化。换句话说，构成网格的每个源在标准立体定向空间中都具有预定且唯一的解剖归属。这允许从多个主体汇集数据并以立体定向坐标报告结果。此外，它允许在相同的解剖框架内优雅地融合 fMRI 和 MEG 数据。
