> I am not sure if this is a power issue

Several possible sources that could contribute to the detection discrepancy, and it's difficult to pin down precisely the exact the reason. For example,

1) not enough number of subjects;
2) suboptimal spatial alignment across modality/subjects;
3) some problematic PPI steps (e.g., deconvolve via 3dTfitter is imperfect).

Even if a cluster fails to survive the rigorous correction, it does not necessarily mean that the results are not worthy reporting. Such results are at least suggestive, and provide some basis for future verifications. Statistical inferences should *not* be a binary decision even though that is very unfortunately what is practiced in the field.

Gang



Edited 1 time(s). Last edit at 11/17/2013 08:06PM by Gang.