Filtering induces correlation in fMRI resting state data
Filtering induces correlation in fMRI resting state data
复制标题
DOI：
10.1016/j.neuroimage.2012.08.022
复制
发表时间：
2013-01-01
期刊：
影响因子：
5.7
通讯作者：
Johnston, Leigh A.
中科院分区：
文献类型：
--
作者：
Davey, Catherine E.;Grayden, David B.;Johnston, Leigh A.
基于相关性的功能性MRI连通性方法通常对数据施加时间样本独立性假设。然而，传统的使用时间滤波来解决fMRI数据的高噪声含量可能会引入样本依赖性。违反独立性假设的样本相关性的分布，如果不考虑，可能会导致无效的连接结果的后果。为了能够使用时间滤波来抑制噪声，同时保持连接结果的完整性，我们推导出滤波时间序列之间的样本相关性的分布作为滤波器频率响应的函数。校正的分布也来自过滤时间序列之间的样本相关性的统计推断测试，包括Fisher的z-变换和学生的t-检验。最重要的是，建议的修正是有效的任何未知的真实相关性和任意滤波器规格。经验模拟证明了时间滤波通过引入样本依赖性来人工诱导连接的潜力，并验证了所提出的校正在减轻这种影响方面的实用性。我们的校正的重要性在静息状态fMRI连接分析中得到了体现：从使用未校正的测试变量的滤波数据生成的种子-体素相关图产生到左初级运动皮层的不可行数量的连接，这表明人工诱导的连通性，而使用校正的测试变量从过滤的数据获得的图在初级运动皮层中表现出双侧连通性，与文献中看到的预期结果一致。(C)2012 Elsevier Inc. All rights reserved.
Correlation-based functional MRI connectivity methods typically impose a temporal sample independence assumption on the data. However, the conventional use of temporal filtering to address the high noise content of fMRI data may introduce sample dependence. Violation of the independence assumption has ramifications for the distribution of sample correlation which, if unaccounted for, may invalidate connectivity results. To enable the use of temporal filtering for noise suppression while maintaining the integrity of connectivity results, we derive the distribution of sample correlation between filtered timeseries as a function of the filter frequency response. Corrected distributions are also derived for statistical inference tests of sample correlation between filtered timeseries, including Fisher's z-transformation and the Student's t-test. Crucially, the proposed corrections are valid for any unknown true correlation and arbitrary filter specifications. Empirical simulations demonstrate the potential for temporal filtering to artificially induce connectivity by introducing sample dependence, and verify the utility of the proposed corrections in mitigating this effect The importance of our corrections is exemplified in a resting state fMRI connectivity analysis: seed-voxel correlation maps generated from filtered data using uncorrected test variates yield an unfeasible number of connections to the left primary motor cortex, suggesting artificially induced connectivity, while maps acquired from filtered data using corrected test variates exhibit bilateral connectivity in the primary motor cortex, in conformance with expected results as seen in the literature. (C) 2012 Elsevier Inc. All rights reserved.