Hi Lauren,

It ought to be reassuring that you keep getting the same
result, particularly after using something relatively automated
like afni_proc.py. Note that you can test the contributions of
tissue-based regressors in afni_proc.py using the -regress_ROI
option (takes any of brain, GM, WM, CSF, where 'brain' is the
whole brain mask, from which the global signal is generated).

It is certainly odd that global signal regression did not have much
of an effect, but that might depend on where the seed is placed.
Also, how much of a negative result is seen will depend on where
the seed is placed. In many places, the result is fairly positive.

With a seed in the left amygdala, for example, I see only a small
fraction of negative results, and they are all insignificant, so any
thresholding wipes them out.

- rick