Fmriprep: pick middle of ribbon when doing EPI-to-surface projection

1

Dear fmriprep experts,

I found that when fmriprep does projection from EPI to fsaverage space, it equally samples 6 points between pial surface and white-matter surface and averages them. But instead, if I want to only pick the middle point of the ribbon, is there a way to modify fmriprep code to achieve this?

This line of code (https://github.com/poldracklab/fmriprep/blob/bbbb2a81734c4eb16331bbb08cb5f3b012e7a358/fmriprep/workflows/bold/resampling.py#L124) seems doing it. Can I achieve my goal by simply changing this line to be:

fs.SampleToSurface(sampling_method=‘average’, sampling_range=(0.5),
sampling_units=‘frac’, interp_method=‘trilinear’, cortex_mask=True,
override_reg_subj=True, out_type=‘gii’),

Thank you!

Regards,
Jingwei

2

You’ll also need to change sampling_method to 'point', but yes that should work.

3

Thanks, Chris. I will try and see how it works. :slightly_smiling_face:

Best,
Jingwei

4

@Jingwei_Li hat’s the justification for choosing one projection strategy over the other?

5

We are going to explore that. The reason why we consider that is by using our own preprocessing pipeline and perform Yeo2011 parcellation algorithm, we got auditory/motor parcels split, but we didn’t replicate this auditory-motor split when using fmriprep on the same set of subjects. We are guessing there might be some information leakage through cortical ribbon.

6

Interesting - please share what you will find!