Because the surface data in our Cifti files is mapped from the volume using subject-specific surfaces, it avoids mixing csf and white matter data into the cortical signal. With a volume parcellation, in order to do something similar, you would need to parcellate each individual somehow, or have an overly generous parcellation and mask it with the per-subject cortical segmentation.
Indeed, putting surface and volume data into one file is the main feature of the Cifti format (though it also has additional mapping types, notably being able to represent a parcellated file in a way that is easy to use for visualization). Cifti also allows the exclusion of vertices and voxels that we aren't interested in (medial wall, white matter, csf, skull, air, etc), which means that some translation is needed in order to use spatial relationships between elements. If you want the gory details, suitable for those implementing their own reader/writer for cifti in other programming languages, see the NITRC page: http://www.nitrc.org/projects/cifti/ The good news is, if you have a parcellation you want to use, and can get it into a cifti label file (see -volume-label-to-surface-mapping and -cifti-create-label), then you can easily parcellate a cifti file with the "wb_command -cifti-parcellate" command. Tim On Wed, Nov 25, 2015 at 2:53 PM, Harms, Michael <[email protected]> wrote: > > If you want connectivity matrices based on a parcellation that respects > the cortical surface, then you'll need to use the CIFTI data, and you'll > need a parcellation to go along with it that is also based on the surfaces > (for the cortical grayordinates). We would definitely suggest that you go > this route, since much of the HCP effort, from acquisition through > processing, is designed around surface-based analyses of the cortical data. > > Also, you probably want to use the "FIX" cleaned data, which has "*clean*" > in the file name, rather than just the minimally pre-processed > .dtseries.nii. > > I think the basic file types are well documented in the release > documentation. > > cheers, > -MH > > -- > Michael Harms, Ph.D. > ----------------------------------------------------------- > Conte Center for the Neuroscience of Mental Disorders > Washington University School of Medicine > Department of Psychiatry, Box 8134 > 660 South Euclid Ave. Tel: 314-747-6173 > St. Louis, MO 63110 Email: [email protected] > > From: Joelle Zimmermann <[email protected]> > Date: Wednesday, November 25, 2015 2:40 PM > To: Timothy Coalson <[email protected]> > Cc: "[email protected]" <[email protected]> > Subject: Re: [HCP-Users] CIFTI and NIFTI -parcellating rfMRI > > Hi Tim, > > Thanks for your response. Within the Resting State fMRI 1 preprocessed in > the 500 Subjects + MEG2, I see the rfMRI_REST1_LR.nii.gz, which I presume > is the Nifti-1 data. And then I see an rfMRI_REST1_LR_Atlas.dtseries.nii - > Is that the dtseries.nii Cifti you refer to? Could you explain a bit more > about what's special about the Cifti file? I understand it Cifti is able to > handle surface vertices and subcortical voxels in one file (i.e. gray > ordinates). > > My ultimate goal is to parcellate the brain into cortical regions of > interest, in order to ultimately look at regional functional connectivity > matrices. Do I need the dtseries.nii cifti for that? It seems like the > advantage of that is having surface vertices (i.e. knowing the precise > shape of the surface of the brain) - which I don't think I need for a > standard FC matrix... > > Thanks, > Joelle > > On Tue, Nov 24, 2015 at 6:16 PM, Timothy Coalson <[email protected]> wrote: > >> The .nii.gz files are nifti-1 volumes, while the .dtseries.nii files are >> Cifti files. If you need spatial information, converting Cifti to nifti-1 >> is not the way to go about it, instead you could use wb_command >> -cifti-separate into metric (.func.gii, one per hemisphere) and volume >> files, or use whatever -cifti-* commands are applicable to what you want to >> do spatially. >> >> Tim >> >> >> On Tue, Nov 24, 2015 at 11:14 AM, Joelle Zimmermann < >> [email protected]> wrote: >> >>> Hi all, >>> >>> I'm working with the 500subjects + MEG2 preprocessed Resting State fMRI >>> 1 Preprocessed dataset. >>> >>> Is the data just standard voxel-wise Nifti (it indeed looks like >>> Nifti-1), or is it in a Cifti format that I need to convert to Nifti? My >>> goal is to parcellate this data into ROI's, and I have a script that does >>> this based on voxel-wise data, but as I understand Cifti is in gray >>> ordinates. >>> >>> Thanks, >>> Joelle >>> >>> _______________________________________________ >>> HCP-Users mailing list >>> [email protected] >>> http://lists.humanconnectome.org/mailman/listinfo/hcp-users >>> >> >> > _______________________________________________ > HCP-Users mailing list > [email protected] > http://lists.humanconnectome.org/mailman/listinfo/hcp-users > > > ------------------------------ > > The materials in this message are private and may contain Protected > Healthcare Information or other information of a sensitive nature. If you > are not the intended recipient, be advised that any unauthorized use, > disclosure, copying or the taking of any action in reliance on the contents > of this information is strictly prohibited. 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