AFNI version info (afni -ver):
Dear AFNI Team,
Where can I find information about the
- regress_bandpass
function in afni_proc.py?
Especially, what window type is used?
Thank you so much!
Hi, Angelika-
We have some descriptions of bandpassing in afni_proc.py in this paper, which would likely be the best place to look:
- Reynolds RC, Glen DR, Chen G, Saad ZS, Cox RW, Taylor PA (2024). Processing, evaluating and understanding FMRI data with afni_proc.py. Imaging Neuroscience 2: 1–52.
Note that part of that is a description of why standard low-frequency fluctuation bandpassing to ~0.01-0.1 Hz in resting state FMRI should probably not be recommended in most cases, even though it is a near-default in many papers in the field.
When doing bandpassing as part of processing, afni_proc.py does bandpassing within the regression model, because that is mathematically appropriate (see again the above paper for description of why this is). Therefore, in typical FMRI processing, bandpassing should be a simple "boxcar window" operation---the frequencies are either in or out. Separately bandpassing out to a separate processing step, wherein one could theoretically taper or smoothly window the bands, is not really mathematically appropriate. (NB: bandpassing+regression could be separated out, as long as the bandpassing were done first and all the regressors in the regression model were also bandpassed in the same way; but that would still preclude tapering.)
Separately and/or if I have misunderstood your question, if you are looking for various programs in AFNI that do bandpassing in some form, you might want to check out this webpage of Classified Programs (that is, programs grouped/classified by topics with brief descriptions, that you can search for usefully on the giant page).
--pt