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Dear Juergen, Please check that you have the most recent version of our WFU_PickAtlas (version 2.4) from http://ansir.wfubmc.edu/. Also note, an increase in the resels can occur if there are more voxels in your mask than in your statistical map. If you would be so kind as to send the appropriate files, we would be glad to look into this further. Ben Wagner ANSIR Lab -----Original Message----- From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] On Behalf Of Juergen Haenggi Sent: Friday, May 30, 2008 2:58 AM To: [log in to unmask] Subject: Re: [SPM] Relatioin between voxels and resels Dear Anderson, dear SPM statistics experts The dimension and resolution of the spmT_000X image is exactly the same as the mask (182x218x182; 1mm x 1 mm x 1mm) used for SVC. Although the search volume decreased by about 130'000 voxels in the SVC analysis, the number of resels increased by 206. The FWHM is also exactly the same in both images (see attachment). What happens? This is a strange behaviour of RFT, right? Best regards Juergen PS: we have done a multiple regression analysis with SPM5 Upd1111 On 30.5.2008 5:06 Uhr, "Anderson Winkler" <[log in to unmask]> wrote: > Dear Juergen, > > It may happen if for some reason you have an estimated FHWM smaller > than your voxel size. However, I don't believe the estimation of the > smoothness is incorrect, otherwise you'd have observed the same even > before using the WM mask. > > Here is one suggestion: check the voxel size of the images you've used > to make the analysis and compare to the voxel size of the mask you're > using. To calculate the resel count, the previously estimated FWHM is > multiplied by the ratio between the voxel size of the original and the > voxel size of the mask (spm_VOI.m, lines 115 and 124). If the > resolution of the mask is lower than the images used to estimate the > smoothness, this may result in a higher number of resels being reported. > > Hope this helps, > > Kind regards, > > Anderson > ----------------------------------------------------------- Juergen Haenggi Ph.D. (Dr. des.) Division of Neuropsychology Institute of Psychology University of Zurich Binzmuehlestrasse 14, PO Box 25 8050 Zurich, Switzerland 0041 44 635 73 97 (phone office) 0041 76 445 86 84 (phone mobile) 0041 44 635 74 09 (fax office) BIN 4.D.04 (office room number) [log in to unmask] (email) http://www.psychologie.uzh.ch/neuropsy/ (website) http://www.juergenhaenggi.ch (private website) -----------------------------------------------------------