REST-VMHC

论坛老师好！
首先感谢REST新版的发布，新版加入VMHC后，我阅读了一些相关的文献，想做VMHC在疾病中的分析，但文献中有些步骤不太懂，望大家帮忙。

1. “The residual time series for each subject was registered to a symmetric MNI template and was used to compute the homotopic functional connectivity.”
“To account for geometric differences between hemispheres, we refined the registration from individual anatomical to MNI152 template space using a group-specific symmetrical template. All 49 registered structural images were averaged to create a mean image, which was then averaged with its left-right mirror to generate a group-specific symmetrical template. Nonlinear registration to this symmetrical template was performed for each participant, and the resultant transformation was applied to each participant's preprocessed functional data.”

对于上述两段文献内容的问题： 上述文献中，因为大脑两侧结构的差异，在预处理FunImgARWSDFC后，又将功能像配准到一个symmetric MNI template，在此请问：这个模板怎么制作？上面第二段话提供了制作方法，即将所有受试标准化后的结构像平均，但下面这一步怎么实现？then averaged with its left-right mirror to generate a group-specific symmetrical template。

2. The analyses were masked by a gray matter segmentation of the symmetric MNI template (thresholded at 40%).
在配准到symmetric MNI template后，接着得出VMHC图，VMHC图限制在该模板的灰质部分，那么这个对模板的灰质分割怎么做，像通常处理结构像一样，简单跑一个VBM就可以吗？

3. 因为两侧对应voxel的z值是相同的，那么在对VMHC图做双样本t检验时，是不是应该以一侧为mask，而不是两侧全脑？如果用Gaussian Random Field theory校正不会涉及这个问题，但AlphaSim就有这个问题。

先谢谢了！