一种用于解决受眼动伪迹污染的脑磁图逆问题的分层贝叶斯方法。

A hierarchical Bayesian method to resolve an inverse problem of MEG contaminated with eye movement artifacts.

作者信息

Fujiwara Yusuke, Yamashita Okito, Kawawaki Dai, Doya Kenji, Kawato Mitsuo, Toyama Keisuke, Sato Masa-aki

机构信息

Graduate School of Information Science, Nara Institute of Science and Technology, Nara 630-0192, Japan.

出版信息

Neuroimage. 2009 Apr 1;45(2):393-409. doi: 10.1016/j.neuroimage.2008.12.012. Epub 2008 Dec 25.

Abstract

The magnetic fields generated by eye movements are major artifacts in MEG measurements. We propose a hybrid hierarchical variational Bayesian method to remove eye movement artifacts from MEG data. Our method is an extension of the hierarchical variational Bayesian method for MEG source localization proposed by Sato et al. [Sato, M., Yoshioka, T., Kajihara, S., Toyama, K., Goda, N., Doya, K., and Kawato, M., (2004). Hierarchical Bayesian estimation for MEG inverse problem. NeuroImage 23(3), 806-826]. First, we assumed a single dipole at each left and right eyeball as a source of eye artifacts. Second, we constructed an EOG forward model describing the relationship between eye dipoles and electric potentials, i.e., EOG. Based on the Bayesian framework, the proposed method concurrently estimates eye and brain current sources from both MEG and EOG data. Thereby the brain current sources can be isolated from eye artifacts. The new method was tested in two ways. In the simulation experiments, the performance of eye artifact removal was evaluated from various aspects; locations of brain current sources, temporal correlation between eye and brain current sources, the level of MEG observation noise and so on. In real MEG experiments, we measured MEG and EOG data during smooth pursuit eye movements for a horizontally or circularly moving target. Our method successfully removed eye artifacts from the simulated and real MEG data with the estimation of brain current sources that were located in eye movement related areas. Our method should be widely applicable to MEG data obtained in tasks with non-negligible eye movements.

摘要

眼球运动产生的磁场是脑磁图(MEG)测量中的主要伪迹。我们提出了一种混合分层变分贝叶斯方法,用于从MEG数据中去除眼球运动伪迹。我们的方法是对Sato等人[Sato, M., Yoshioka, T., Kajihara, S., Toyama, K., Goda, N., Doya, K., and Kawato, M., (2004). Hierarchical Bayesian estimation for MEG inverse problem. NeuroImage 23(3), 806 - 826]提出的用于MEG源定位的分层变分贝叶斯方法的扩展。首先,我们假设左右眼球各有一个偶极子作为眼球伪迹的来源。其次,我们构建了一个眼电图(EOG)正向模型,描述眼球偶极子与电势之间的关系,即EOG。基于贝叶斯框架,所提出的方法同时从MEG和EOG数据中估计眼球和脑电流源。从而可以将脑电流源与眼球伪迹分离。新方法通过两种方式进行了测试。在模拟实验中,从各个方面评估了去除眼球伪迹的性能;脑电流源的位置、眼球和脑电流源之间的时间相关性、MEG观测噪声水平等。在实际的MEG实验中,我们在对水平或圆周运动目标进行平稳跟踪眼球运动期间测量了MEG和EOG数据。我们的方法通过估计位于眼球运动相关区域的脑电流源,成功地从模拟和实际的MEG数据中去除了眼球伪迹。我们的方法应广泛适用于在眼球运动不可忽略的任务中获得的MEG数据。

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