Dear Rick,

Thanks a lot for your response! Removing only drift at 1/320 Hz might be sensitivity-inefficient. It might be expected that low frequency drifts are either related to the scanner or to the task-unrelated physiology and thus they should be removed. Otherwise, the low frequency drifts decrease the sensitivity for task-fMRI analyses. In FSL and SPM by default all low-frequency drifts below 1/100 and 1/128 are removed, and I usually see more significant activation when I make this cutoff frequency higher.

The polort function is from 3dDeconvolve, sorry for not clarifying that in my original post!

So my current understanding is that for an ordinary single-subject fMRI analysis, afni_proc.py will by default remove the very, very low frequency drift using polort (even if I do not directly call polort), and if I want to remove other low-frequency drifts I should use regress_bandpass. Am I correct?

However, AFNI help for regress-bandpass says:

-regress_bandpass lowf highf : bandpass the frequency range
e.g. -regress_bandpass 0.01 0.1
This option is intended for use in resting state analysis.

and so it suggests it is not for task-based data. How to interpret it?

Best,

Wiktor Olszowy



Edited 1 time(s). Last edit at 09/25/2017 11:31AM by wo222.