Hello, I noticed that the following difference between the default processing pipeline and another pipeline:

For the default preprocessing pipeline for volume-based analyses (direct normalization to MNI-space):

it shows "functional realignment with correction of susceptibility distortion interactions (subject motion estimation and correction)"

For the 3rd preprocessing pipeline for volume-based analyses (direct normalization to MNI-space) when field maps are available:

it shows "functional realignment with susceptibility distortion correction using field maps (subject motion estimation and correction)"

It seems that they are both performing susceptibility distortion correction, but the default processing pipeline does not use the field map to do it. The tutorial said the field map was optional, and did not provide much detail on how to do it.

My questions would be:
1) Is it OK to just use the default processing pipeline?
2) How much of a difference would it make if we use the field map to do susceptibility distortion correction?
3) How do we create a secondary dataset?
There was another post that talked about "define a new secondary dataset in Setup.Functionals and name/label it 'fmap'. But I am not sure how to do it, I couldn't find any button or menu that allows me to define/create a new secondary dataset.

Thanks so much! Any help or suggestion would be appreciated.