Carolina,
It means its smoothing on the surface with a kernel of 10mm full-width half-max. Smoothing on the surface can generally be larger than in a volume. See these slides for a description of the difference:
http://surfer.nmr.mgh.harvard.edu/pub/docs/fs.surface-based-analysis.ppt
you can use a lower fwhm, it just depends on your expected blob size (there is no formula for the 'right' smoothing level).
Nick
Hello,
<div>In the qdec analysis the default smoothing factor is 10. What does it mean? For other technics such as fMRI we generally use a lower smoothing factor (~3 or lower). What would happen if I low down the FWHM?</div> <div>Thank you, Carolina</div> _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
Hi Carolina, the FWHM is the "full-width/half-maximum" and indicates how much smoothing you have. This is surface-based smoothing, not volume based, and it can be difficult to compare to volume based smoothing as is done in fMRI. The surface-based smoothing can be larger because you don't have to worry about smoothing in white matter and CSF or jumping across a sulcus as you would at higher levels of volume-based smoothing. There is no answer to the actual level of smoothing you need because it depends on how big the blob is. 10mm is "typical". fMRI analysis often has this level of smoothing in the volum.e doug
On 07/07/2012 02:44 PM, carolina.mr wrote:
Hello, In the qdec analysis the default smoothing factor is 10. What does it mean? For other technics such as fMRI we generally use a lower smoothing factor (~3 or lower). What would happen if I low down the FWHM? Thank you, Carolina
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Nick Schmansky