Hi Martin there is no easy answer to this question. Basically, the optimal smoothing filter depends on the size of the effect you are looking for (the so-called "matched-filter theorem"). IN general, if you have bigger groups of subjects and/or expect focal differences use a smaller kernel.
Sorry I don't have better advice to give than that cheers Bruce On Wed, 16 Mar 2016, Martin Juneja wrote: > Hello everyone, > I am very new to FreeSurfer. Although I know what smoothing means etc. but I > am not sure what smoothing level is the best to choose while comparing > cortical thinning for patients vs. controls. Qdec gives several options to > choose from among 0, 5, 10, 15, 20 and 25. > Literature says 10 mm is the typical value to choose but when I calculate > clusters, I don't see any significant clusters (at FDR p < 0.05) but at > smoothing level 20 mm, I can see several clusters at the same threshold i.e. > at FDR p < 0.05. > > I would really appreciate if someone, expert in this field could guide me > regarding this. Also, may be if someone could recommend me a few papers from > literature discussing this issue e.g. effect of smoothing on cortical > thickness etc., that would be very useful. > > Thanks, > MJ > > _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer 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.
