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Doron - SPM does not separate error into between- and within-subject components. So I would do the following. Take a subject and use ImCalc to select the scans corresponding to their two timepoints. First, evaluate the function "i1-i2", and call this, say, "dif_grp01_sub01" for group 1, subject 1. Then select the same scans again, but evaluate "i1+i2", and call this, say, "com_grp01_sub01". Repeat for each group/subject. (You can automatize by calling spm_imcalc_ui.m from the command line, if you like). Now, if you had 2 groups of 12 subjects, you should have 2 x 12 = 24 images starting "dif_*", and 24 starting "com_*". Then, for the ANOVA main effect of time, choose a "two-sample t-test" in the Basic Stats option of SPM2 (i.e, unpaired t-test), and enter the 12 "dif_*" scans for group 1 as the first sample, and the 12 scans for group 2 as the second sample. Then evaluate the F-contrast [1 1]. For the ANOVA time x group interaction, use the same design matrix as above, but now test the F-contrast [1 -1]. For the ANOVA main effect of group, create a new "two-sample t-test", but enter the scans "com_*" for each group, and evaluate the F-contrast [1 -1]. Hope this helps Rik -------------------------------------------------------- DR RICHARD HENSON MRC Cognition & Brain Sciences Unit 15 Chaucer Road, Cambridge, CB2 2EF England EMAIL: [log in to unmask] URL: http://www.mrc-cbu.cam.ac.uk/~rik.henson TEL +44 (0)1223 355 294 x522 FAX +44 (0)1223 359 062 MOB +44 (0)794 1377 345 -------------------------------------------------------- > -----Original Message----- > From: Doron Gothelf [mailto:[log in to unmask]] > Sent: 03 May 2005 19:09 > To: [log in to unmask] > Subject: VBM repeated measures ANOVA > > > Dear Rob > I have seen that you inquired about the possibility of running > repeated measures ANOVA in MATLAB/SPM for VBM data. I encountered the > same problem. I have 2 time points of VBM scans (within subject > differences or effect) and 2 groups of subjects (between group > differences or effect) and I am also interested in the interaction > (time by group). Could you instruct me from what you learn what > should I do? > > Thanks > > Doron Gothelf, M.D. > Department of Child Psychiatry > Stanford University >