If you don't care about extending your results beyond your sample, then an FFx is fine. doug
SHAHIN NASR wrote: > Do you suggest using random-effect model? Is there any problem with > using a fix-effect model (other than the fact that by using this model > we can not predict response of subjects outside our population)? > > On Wed, Oct 19, 2011 at 3:07 PM, Douglas N Greve > <gr...@nmr.mgh.harvard.edu <mailto:gr...@nmr.mgh.harvard.edu>> wrote: > > > It should be roughly the sum of the dofs of the individual > subjects. Why are you using a fixed-effects model? > doug > > SHAHIN NASR wrote: > > Thanks Doug. Just one related question. Should I also > generate a new ffxdof.dat file for this map? I assumed that > ffxdof depends on the number of subjects (session) and since > number of subjects (sessions) is the same between the two > groups then I can use those values, generated by > isxconcat-sess for either map1 or map2. Right? > > > > On Wed, Oct 19, 2011 at 1:33 PM, Douglas N Greve > <gr...@nmr.mgh.harvard.edu <mailto:gr...@nmr.mgh.harvard.edu> > <mailto:gr...@nmr.mgh.harvard.edu > <mailto:gr...@nmr.mgh.harvard.edu>>> wrote: > > Hi Shahin, it is not as simple as doing a subtraction of the > cesvar files. What you are trying to get is the expected > variance > of your difference between the ces files (as a variance, it > must > be positive). To get this you need > > cesvardiff = (cesvar1+cesvar2)/(2^2) > > The 2^2 is the number of inputs (2) squared. > > doug > > > SHAHIN NASR wrote: > > Hi, > > I have generated two different functional connectivity > maps > for two different ROI-based seeds. These maps are based on > group-average of the same subjects (generated by using > separate isxconcat-sess commands ), and now I want to > see the > difference map. To do so, I used mris_calc as below. > > mris_calc -o diff_map/rh.ces.nii map1/rh.ces.nii > sub map2/rh.ces.nii > > Also, to generate the rh.cesvar.nii file I used this > command: > > mris_calc -o diff_map1/rh.cesvar.nii > map1/rh.cesvar.nii > sub map2/rh.cesvar.nii > > But then when I used the glmfit with WLS option as below: > > > mri_glmfit --y rh.ces.nii --osgm --glmdir rh.ffx.osgm.wls > --nii --mask ../rh.mask.nii --yffxvar rh.cesvar.nii > --ffxdofdat ../ffxdof.dat --surf fsaverage rh --wls > rh.cesvar.nii > > I faced an error saying: "Error: MRInormWeights: > values less > than or eq to 0" which I assumed is related to an error in > rh.cesvar.nii file (am I right?). Would you tell me how > can I > fix this problem? > > P.S.: please note that sequence of subjects and all MRI > parameters are exactly the same between the two maps. > > -- Shahin Nasr > > PhD in Cognitive Neuroscience > Martinos Imaging Center, MGH > Harvard Medical School > > > -- Douglas N. Greve, Ph.D. > MGH-NMR Center > gr...@nmr.mgh.harvard.edu > <mailto:gr...@nmr.mgh.harvard.edu> > <mailto:gr...@nmr.mgh.harvard.edu > <mailto:gr...@nmr.mgh.harvard.edu>> > Phone Number: 617-724-2358 <tel:617-724-2358> > <tel:617-724-2358 <tel:617-724-2358>> Fax: 617-726-7422 > <tel:617-726-7422> > <tel:617-726-7422 <tel:617-726-7422>> > > Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting > <http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting> > <http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting> > FileDrop: > www.nmr.mgh.harvard.edu/facility/filedrop/index.html > <http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html> > <http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html> > > > > > The information in this e-mail is intended only for the > person to > whom it is > addressed. If you believe this e-mail was sent to you in > error and > the e-mail > contains patient information, please contact the Partners > Compliance HelpLine at > http://www.partners.org/complianceline . If the e-mail was > sent to > you in error > but does not contain patient information, please contact the > sender and properly > dispose of the e-mail. > > > > > -- > Shahin Nasr > > PhD in Cognitive Neuroscience > Martinos Imaging Center, MGH > Harvard Medical School > > > -- > Douglas N. Greve, Ph.D. > MGH-NMR Center > gr...@nmr.mgh.harvard.edu <mailto:gr...@nmr.mgh.harvard.edu> > Phone Number: 617-724-2358 <tel:617-724-2358> Fax: 617-726-7422 > <tel:617-726-7422> > > Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting > <http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting> > FileDrop: www.nmr.mgh.harvard.edu/facility/filedrop/index.html > <http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html> > > > > > -- > Shahin Nasr > > PhD in Cognitive Neuroscience > Martinos Imaging Center, MGH > Harvard Medical School > -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@nmr.mgh.harvard.edu Phone Number: 617-724-2358 Fax: 617-726-7422 Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting FileDrop: www.nmr.mgh.harvard.edu/facility/filedrop/index.html _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
