morph.apply and source space size

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Dear MNE list

Can anyone help me how to keep the resolution of the source space when morphing source estimates from subject MRI space to fs_average. I use the new morphing function in MNE-Python 0.17:

               morph = mne.compute_source_morph(stc_subject, subject, 'fsaverage', subjects_dir=subjects_dir) # New in MNE 0.17
               stc_fsaverage = morph.apply(stc_subject)

When the morphing is comple, it now contain all verticies from fs_average:
stc_subject: <SourceEstimate | 5124 vertices, subject : 0403, tmin : 0.0 (ms), tmax : 0.0 (ms), tstep : 1000.0 (ms), data shape : (5124, 1)
stc_fsaverage: <SourceEstimate | 20484 vertices, subject : fsaverage, tmin : 0.0 (ms), tmax : 0.0 (ms), tstep : 1000.0 (ms), data shape : (20484, 1)>

Is there a way to keep the original number of vertices in the morphed source maps?

In the previous version of MNE-Python morphing had a ?grade? argument:
stc_fsaverage = stc_subject.morph('fsaverage', subjects_dir=subjects_dir, grade=4)

There is the argument ?mri_resolution? in the morph.apply, but it does not seem to alter the scaling. Or maybe I am not giving it the correct argument: it is not 4 nor 5124?

Thank you in advance

Best regards
Mikkel

Mikkel C. Vinding | Ph.D. | Post doc
NatMEG - The National Research Facility for Magnetoencephalography
Department of Clinical Neuroscience | Karolinska Institutet
171 77 Stockholm | Nobels v?g 9, office D313
Phone: +46 8 524 833 33
Email: mikkel.<mailto:mikkel at vinding@ki.se>vinding at ki.se <mailto:mikkel.vinding at ki.se> | ki.se<http://ki.se/ki/jsp/polopoly.jsp;jsessionid=aMdk8ad4iRL6OYOdFn?l=en&d=130>

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