Dear spm-users,
I am trying to investigate potential changes induced by an intervention (noninvasive brain stimulation) on rs-fMRI. So I am running a second level analysis based on a paired t-test with the inputs from my first-level analyses. So far so good. However, I would also like to correct for variations in the strength of the stimulation (4 scalar vectors for every subject). If I make a matrix for these covariate and put that in the 'multiple covariates' input in spm, I can indeed see that these are incorporated in the design matrix (see design here: https://www.dropbox.com/s/4fmvdgfh1sjeh5a/Schermafbeelding%202023-06-20%20om%2016.52.43.png?dl=0). But when I look into my results, I do not see any differences to my analysis without covariates so clearly I am doing something wrong.
If anyone has any advice on how to solve this issue, it would be highly appreciated.
Thank you so much.
Best,
Debby
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