effigies
commented
2 months ago Thanks!
Just to state: fMRIPrep doesn't produce the "correct" number of cosine regressors, it produces those needed for a 128s high-pass cutoff. You are free to use less (or more, if you calculate them yourself).
That said, from https://fmriprep.org/en/stable/outputs.html:
fMRIPrep does high-pass filtering before running anatomical or temporal CompCor. Therefore, when using CompCor regressors, the corresponding cosine_XX regressors should also be included in the design matrix.
Here the point is that you should use all of the cosine regressors if you're going to use CompCor.
If this is unclear, could you propose clearer wording that would you feel would have gotten the point across better?
TrevorKMDay
It's my understanding the number of
cosine_regressors are based on the length of the scan. However, I thought they behaved like the aCompCor regressors, i.e. more than you need are calculated. I spent some time looking for how many to select based on the length of the scan, before finding out fMRIPREP makes that calculation for you and spits out exactly the correct number ofcosine_regressors.I think the documentation could be more explicit about the number of cosine regressors and how fMRIPREP selects them for you.