Department of Biomedical Engineering, National University of Singapore, Singapore; Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research, Singapore; Clinical Imaging Research Center, National University of Singapore, Singapore.
Department of Biomedical Engineering, National University of Singapore, Singapore.
Med Image Anal. 2015 Feb;20(1):52-60. doi: 10.1016/j.media.2014.10.006. Epub 2014 Oct 30.
We propose a new analysis framework to utilize the full information of brain functional networks for computing the mean of a set of brain functional networks and embedding brain functional networks into a low-dimensional space in which traditional regression and classification analyses can be easily employed. For this, we first represent the brain functional network by a symmetric positive matrix computed using sparse inverse covariance estimation. We then impose a Log-Euclidean Riemannian manifold structure on brain functional networks whose norm gives a convenient and practical way to define a mean. Finally, based on the fact that the computation of linear operations can be done in the tangent space of this Riemannian manifold, we adopt Locally Linear Embedding (LLE) to the Log-Euclidean Riemannian manifold space in order to embed the brain functional networks into a low-dimensional space. We show that the integration of the Log-Euclidean manifold with LLE provides more efficient and succinct representation of the functional network and facilitates regression analysis, such as ridge regression, on the brain functional network to more accurately predict age when compared to that of the Euclidean space of functional networks with LLE. Interestingly, using the Log-Euclidean analysis framework, we demonstrate the integration and segregation of cortical-subcortical networks as well as among the salience, executive, and emotional networks across lifespan.
我们提出了一种新的分析框架,利用大脑功能网络的全部信息来计算一组大脑功能网络的均值,并将大脑功能网络嵌入到一个低维空间中,以便于进行传统的回归和分类分析。为此,我们首先使用稀疏逆协方差估计计算对称正定矩阵来表示大脑功能网络。然后,我们在大脑功能网络上施加对数欧式黎曼流形结构,其范数为定义均值提供了一种方便实用的方法。最后,基于线性运算的计算可以在该黎曼流形的切空间中完成这一事实,我们采用局部线性嵌入(LLE)将大脑功能网络嵌入到低维空间中。我们证明了 Log-Euclidean 流形与 LLE 的结合为功能网络提供了更有效和简洁的表示,并促进了回归分析,如岭回归,与基于 LLE 的功能网络的欧几里得空间相比,可以更准确地预测年龄。有趣的是,使用 Log-Euclidean 分析框架,我们展示了皮质-皮质下网络的整合和分离,以及在整个生命周期中突显、执行和情感网络之间的整合和分离。