1) In the documentation, it is written that : we have one row per timepoint/volume.
Is every volume compared to the first volume or to the previous volume?
In general no. In case of DVARS and FramewiseDisplacement the measure is a corresponds to a difference/variance between the corresponding timepoint and the next one (that's why the last value is 'n/a')
2) Are the 6 motion parameters in mm ?
No. Translations are in mm, but rotations are in radians.
3) To process the GLM analysis do we use this following nifti file :
Only if you analyze a single subject of you do withing subjects design. For group analysis (most studies) you need the file in a common space - for example
Can I know why do you prefer aCompCor to tCompCor ? Is it because the mask provided is an anatomical mask so aCompCor is equivalent to CompCor ?
I don't know what do you mean by
CompCor, but I prefer
aCompCor because it is more theory driven.