Hi Rick,

yes, some of the runs indeed go up to two hours. These are sleep recordings and subjects were allowed to sleep in the scanner up to two hours.
I will now try running my script again adding

-regress_polort 2         \
-regress_bandpass 0.01 1

as you suggested, thank you. The option -regress_compute_fitts does not work or make sense here, because I use a resting-state script.

Update: AFNI proc ends up with 147 baseline funcs for over 2100 time points when using polort 2 and bandpass 0.01-1.



Meanwhile, I would like to ask you another question. When I am intersted in the BOLD signal’s power in the frequency-domain, say at around 0.01 Hz, would you recommend to always use a polort degree of 2 in combination with a bandpass filter (instead of using the automatic calculation of polort depending on the run length)?

I read through the message board, and I also read some AFNI .pdf files, but I don't really understand how the polort option affects the BOLD signal (in a comparison before/after preprocessing). It is possible to explain this theoretically in easy words?

So, if I am interested in the frequency spectrum of the signal, and not so much in statistical parametric maps, is there a better way to adjust the -regress_polort option than leaving it at the default autocomputation? But, I assume that there is not one correct answer here, and the appropriate polort option rather depends on many factors?



Edited 3 time(s). Last edit at 05/09/2022 01:47PM by Philipp.