Dear Freesurfer expert,

I hope this email finds you well. I am currently working on a project involving FreeSurfer's cluster-wise correction methods, and I encountered an unexpected result when adjusting the Cluster-Forming Threshold (CFT) and Cluster-Wise Probability (CWP) values. I would greatly appreciate your expertise on this matter.

In my analysis, I observed that some regions were not detected when using a CFT of 1.3 and a CWP of 0.05. However, these regions emerged as significant when I increased the CFT to 2.0 while keeping the CWP constant at 0.05. This finding appears counterintuitive, as a higher CFT typically results in fewer clusters being detected due to the increased threshold for significance.

Could you please help clarify why this phenomenon might occur? Specifically:

1. How might the higher CFT (2.0) interact with the CWP (0.05) to reveal regions that did not appear with a lower CFT (1.3)?
2. Is it possible that the increase in CFT reduces noise or increases signal clarity in such a way that previously undetected clusters reach significance?

Thank you very much for your time and guidance. I look forward to any insights you can provide on this topic.

Jonghun Lee
Master's Student, Advanced Image Processing Technology Lab
Yonsei University