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Hi Volkmar thank you so much for writing back to me. I really appreciate your detailed answer. Just one more question on smoothness, I applied 0.5 mm in all the directions. Is it better to use a different smoothing kernel for the Z direction in my case since the x and y are isotropic. thank you Best regards Payal On Wed, Dec 5, 2018 at 5:39 AM Volkmar Glauche < [log in to unmask]> wrote: > Hi Payal, > SPMs smoothness estimate will always depend on the smoothness of your > measurement and the smoothing kernel you applied to your data before fMRI > statistics. Since your measurement is 3-4 times smoother in z direction > compared to x and y, SPM will detect a larger smoothness in z direction > unless you applied a very large smoothing kernel also in x and y direction. > This is a property of your preprocessed data and should not be a problem. > (There are other cases, where SPM underestimates smoothness, which are > often caused by measurement problems. This doesn't apply to your case, so > you should be safe.) > You should not need to resample your atlas to match the functional data. > If the atlas and the functional data are in rough realignment to each other > (without reslicing) then coregistration, normalisation... should work > regardless of atlas and fMRI resolution. > Best, > Volkmar >