Lee Adél, Särkkä Aila, Madhyastha Tara M, Grabowski Thomas J
Etosha Business and Research Consulting, Mount Berry, GA, 30149, USA.
Department of Mathematical Sciences, Chalmers University of Technology and University of Gothenburg, 41296, Gothenburg, Sweden.
Biom J. 2017 Nov;59(6):1352-1381. doi: 10.1002/bimj.201600212. Epub 2017 Jul 12.
We develop a two-stage spatial point process model that introduces new characterizations of activation patterns in multisubject functional Magnetic Resonance Imaging (fMRI) studies. Conventionally multisubject fMRI methods rely on combining information across subjects one voxel at a time in order to identify locations of peak activation in the brain. The two-stage model that we develop here addresses shortcomings of standard methods by explicitly modeling the spatial structure of functional signals and recognizing that corresponding cross-subject functional signals can be spatially misaligned. In our first stage analysis, we introduce a marked spatial point process model that captures the spatial features of the functional response and identifies a configuration of activation units for each subject. The locations of these activation units are used as input for the second stage model. The point process model of the second stage analysis is developed to characterize multisubject activation patterns by estimating the strength of cross-subject interactions at different spatial ranges. The model uses spatial neighborhoods to account for the cross-subject spatial misalignment in corresponding functional units. We applied our methods to an fMRI study of 21 individuals who performed an attention test. We identified four brain regions that are involved in the test and found that our model results agree well with our understanding of how these regions engage with the tasks performed during the attention test. Our results highlighted that cross-subject interactions are stronger in brain areas that have a more specific function in performing the experimental tasks than in other areas.
我们开发了一种两阶段空间点过程模型，该模型引入了多受试者功能磁共振成像（fMRI）研究中激活模式的新特征。传统的多受试者fMRI方法依靠一次一个体素地合并受试者间的信息，以识别大脑中峰值激活的位置。我们在此开发的两阶段模型通过明确对功能信号的空间结构进行建模，并认识到相应的跨受试者功能信号可能在空间上未对齐，解决了标准方法的缺点。在我们的第一阶段分析中，我们引入了一个标记空间点过程模型，该模型捕获功能反应的空间特征，并为每个受试者识别激活单元的配置。这些激活单元的位置用作第二阶段模型的输入。第二阶段分析的点过程模型旨在通过估计不同空间范围内跨受试者相互作用的强度来表征多受试者激活模式。该模型使用空间邻域来考虑相应功能单元中的跨受试者空间未对齐情况。我们将我们的方法应用于一项对21名进行注意力测试的个体的fMRI研究。我们确定了四个参与该测试的脑区，并发现我们的模型结果与我们对这些区域如何参与注意力测试期间执行的任务的理解非常吻合。我们的结果突出表明，在执行实验任务时具有更特定功能的脑区中，跨受试者相互作用比其他区域更强。
