Hello,

I am currently trying to perform voxel-to-voxel analyses on subjects from two different datasets. When I try to run any analysis in the voxel-to-voxel category, I get the following error:

"Unequal analysis voxels across subjects. Modify 'spatial resolution' and/or 'analysis mask' fields in Setup->Options to match analysis voxels across subjects"

I have gotten around this by running the ICA and selecting only the new subjects I want to add, and now I assume that in the 2nd level results I am looking at both datasets combined, but I don't know if this is the correct way of doing things.

Otherwise I will have to try and fix this voxel number but I am not sure how to go about doing that?

Sorry if the answer to this if fairly obvious, but any help would be appreciated!

Thank you very much,
Kaija

Hi Kaija,

Not exactly. Since group-ICA is basically a group-level analysis, running ICA twice, each on different groups of subjects, is not the same running it once on the entire dataset. I would recommend to first resample your data to the same resolution using one of the methods below, and then re-run ICA on the entire dataset. 

method 1) if your data is already in MNI-space, then select in Setup.Options the default 'Volume: same as mask' option in the'Analysis space (voxel-level)' menu, and the 'Explicit mask (mask.volume.brainmask.nii)' option in the 'Analysis mask (voxel-level)' menu, and re-run the Setup&Denoising steps (that will have CONN automatically resample your data to 2mm voxels jointly across all subjects as part of the Setup step).

method 2) if, on the other hand, your functional data is not yet in MNI-space, then normalize your data first (e.g. run a "functional normalization" preprocessing step, in Setup -> Preprocessing), and then follow method (1) above. 

Best
Alfonso 
Originally posted by kaija:

Hi Alfonso,

Thank you so much, this seems to have done the trick!!

Best,
Kaija

Originally posted by Alfonso Nieto-Castanon: