Di Xin, Biswal Bharat B
Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, United States.
Front Neurosci. 2017 Oct 17;11:573. doi: 10.3389/fnins.2017.00573. eCollection 2017.
Psychophysiological interaction (PPI) is a regression based method to study task modulated brain connectivity. Despite its popularity in functional MRI (fMRI) studies, its reliability and reproducibility have not been evaluated. We investigated reproducibility and reliability of PPI effects during a simple visual task, and examined the effect of deconvolution on the PPI results. A large open-access dataset was analyzed ( = 138), where a visual task was scanned twice with repetition times (TRs) of 645 and 1,400 ms, respectively. We first replicated our previous results by using the left and right middle occipital gyrus as seeds. Then regions of interest (ROI)-wise analysis was performed among 20 visual-related thalamic and cortical regions, and negative PPI effects were found between many ROIs with the posterior fusiform gyrus as a hub region. Both the seed-based and ROI-wise results were similar between the two runs and between the two PPI methods with and without deconvolution. The non-deconvolution method and the short TR run in general had larger effect sizes and greater extents. However, the deconvolution method performed worse in the 645 ms TR run than the 1,400 ms TR run in the voxel-wise analysis. Given the general similar results between the two methods and the uncertainty of deconvolution, we suggest that deconvolution may be not necessary for PPI analysis on block-designed data. Lastly, intraclass correlations (ICC) between the two runs were much lower for the PPI effects than the activation main effects, which raise cautions on performing inter-subject correlations and group comparisons on PPI effects.
心理生理交互作用（PPI）是一种基于回归的方法，用于研究任务调制的脑连接性。尽管它在功能磁共振成像（fMRI）研究中很受欢迎，但其可靠性和可重复性尚未得到评估。我们研究了简单视觉任务期间PPI效应的可重复性和可靠性，并检验了去卷积对PPI结果的影响。分析了一个大型开放获取数据集（n = 138），其中对视觉任务进行了两次扫描，重复时间（TR）分别为645和1400毫秒。我们首先以左右枕中回为种子区域复制了我们之前的结果。然后在20个与视觉相关的丘脑和皮层区域之间进行了感兴趣区域（ROI）分析，发现许多ROI之间存在以梭状回后部为中心区域的负PPI效应。基于种子区域和基于ROI的结果在两次扫描之间以及在有无去卷积的两种PPI方法之间都相似。一般来说，非去卷积方法和短TR扫描的效应量更大，范围更广。然而，在体素分析中，去卷积方法在645毫秒TR扫描中的表现比在1400毫秒TR扫描中更差。鉴于两种方法的总体结果相似以及去卷积的不确定性，我们建议对于块设计数据的PPI分析，去卷积可能没有必要。最后，两次扫描之间PPI效应的组内相关系数（ICC）远低于激活主效应，这对进行PPI效应的受试者间相关性分析和组间比较提出了警示。
