Hi Lijie
while SPM (and others) call it "density", it's really just a smoothing of the labeled voxels over space. We tools that would allow you to do the same thing with FS segmentations, but haven't ever put them together into a pipeline as the neurobiological interpretation of such a map is very difficult.
cheers Bruce
On Fri, 18 Feb 2011, soft.join Huang wrote:
Hi, FreeSurfer and VBM experts
I'm a newer in the field, and not sure if this question is relevant to the list - any help will be appreciated.
I am wondering about the difference between the data of FS and that of VBM in SPM. After searching in Google, I find a topic following, url: https://mail.nmr.mgh.harvard.edu/pipermail/freesurfer/2008-May/007710.html, and have some different opinions.
In the discussion in above link, all believe that FS and VBM could give the same measurement - volume, yet I don't think so. I admit that we could get the volume of specific ROI by multiplying the thickness by the surface area, but through VBM in SPM, we get the mass( something like it) of the gray matter( multiply the density of gray matter by the volume). They have different meaning, to the best of my knowledge.
I don't know if I get the right understanding.
Thanks a lot in advance.
Lijie Huang email: huanglijie.seal@gmail.com State Key Laboratory of Cognitive Neuroscience and Learning Beijing Normal University Beijing China