Hi, i would like to do some analysis comparing with/without Global Signal Regression, but most of my preprocessing is already done (motion correction is done, and i used melodic ICA to remove noise).
i was wondering if there is an AFNI function that i can use to solely perform global signal regression on my already-denoised datasets? thanks,
i was wondering if there is an AFNI function that i can use to solely perform global signal regression
on my already-denoised datasets?
One possibility is to obtain the global signal using 3dmaskave and then add it as a regressor in your analysis.
It is best, as Gang implies, to extract the global signal and then include it in your regressions in the pre-processing, which presumably are removing other signals “of no interest”. Regressing one thing out by itself after the other regressions is not usually a proper form of analysis – if you regress out A and then B, the result is not the same as regressing out B and then A (unless A and B are orthogonal).