External Email - Use Caution Thank you so much Dr. Fischl, that information is very helpful.
On Thu, Dec 20, 2018 at 12:18 PM Bruce Fischl <fis...@nmr.mgh.harvard.edu> wrote: > Hi Martin > > you can use whichever surface you want - they are just different > biological questions. The files we write out by default relate to the > white surface, but you can certainly generate the equivalent for the pial > using mris_curvature. > > In general the curvature is 1/r, where r is the radius of an inscribed > circle that is tangent to the surface in that direction. So bigger > curvature implies smaller r (and sharper folds). > > As for you question (2), I think that is a biological one and depends on > the effect you are looking for (unless I am misunderstanding) > > cheers > Bruce > > > On > Thu, 20 Dec 2018, Martin Juneja wrote: > > > > > External Email - Use Caution > > > > Thank you so much every one for helping me in this regard. I have some > follow up questions: > > I am interested in associating mean curvature (H) with some behavioral > measure. After extracting > > subject-wise mean curvature estimates, I found a significant positive > association between mean > > curvature and those behavioral measures. My questions are: > > > > (1). Why did Dr. Greve suggested to use white surface for estimating > mean curvature, and not pial? > > What's the exact differences in both - is the only difference is that > one is used for mean curvature > > from white matter (white surface) and the other from gray matter? I am > not sure why one is > > recommended over the other? > > (2). If I want to use my own spherical ROIs for mean curvature > estimation, how much radius is enough > > to draw spheres around peak coordinates? > > (3). Using white surface as recommended as Dr. Greve, I get (-) values > for all the subjects, please > > see attached plot. Here mean curvature values are plotted along Y-axis. > So here more negative values > > (.e.g ~ -0.07) represent sharper folds or less negative values (e.g. ~ > -0.04) represent sharper > > folds? If I take absolute values of mean curvature, this association > shown in attached plot changes > > from positive to negative. Can you please help me in interpreting the > differences in more negative > > and less negative values here? > > > > Any additional information about this measure will also be very useful, > as I am using this parameter > > for the first time. > > > > Thanks a lot. > > > > On Wed, Dec 19, 2018 at 4:24 PM Bruce Fischl <fis...@nmr.mgh.harvard.edu> > wrote: > > a 2D manifold has two principal curvatures, usually called k1 and > k2, > > which are the curvature in the direction of maximum curvature and > minimum > > curvature (they are also the eigenvalues and eigenvectors of the > Hessian of > > the surface if it is expressed as a function over the tangent > bundle). The > > Gaussian (K) and mean (H) curvatures are then: > > > > K = k1*k2 > > H = (k1+k2)/2 > > > > cheers > > Bruce > > > > > > On Wed, 19 Dec 2018, Greve, Douglas N.,Ph.D. wrote: > > > > > I'll leave that up to Bruce and Rudolph > > > > > > On 12/19/2018 05:37 PM, Martin Juneja wrote: > > >> > > >> External Email - Use Caution > > >> > > >> Thanks Dr. Greve. That works, but both white.K and white.H are > giving > > >> me very different output values. > > >> > > >> For example, for first few subjects I get: > > >> -0.00237 -0.00450 -0.00204 0.00113 -0.00228 > -0.00958 > > >> -0.00314 0.00180 -0.00452 if I use white.K > > >> -0.05809 -0.05799 -0.06457 -0.07254 -0.07208 > -0.05023 > > >> -0.06044 -0.09338 -0.09178 if I use white.H > > >> > > >> Can you please tell me the difference between white.K and > white.H > > >> conceptually and mathematically? > > >> > > >> On Wed, Dec 19, 2018 at 2:27 PM Greve, Douglas N.,Ph.D. > > >> <dgr...@mgh.harvard.edu <mailto:dgr...@mgh.harvard.edu>> wrote: > > >> > > >> something like --meas white.K or white.H > > >> > > >> > > >> On 12/19/2018 04:23 PM, Martin Juneja wrote: > > >> > > > >> > External Email - Use Caution > > >> > > > >> > Hi, > > >> > > > >> > Just like volume, I have "Folding Index" measures saved in > > >> > lh/rh.aparc.stats files for each subject. > > >> > > > >> > If I am using mris_preproc *--meas volume* --out > CV/lh.CV.mgh > > >> command > > >> > to concat cortical volume files from all subjects, then > how can > > >> I use > > >> > this command for "folding index" output file? > > >> > > > >> > Any help will be really appreciated. > > >> > > > >> > > > >> > _______________________________________________ > > >> > Freesurfer mailing list > > >> > Freesurfer@nmr.mgh.harvard.edu > > >> <mailto:Freesurfer@nmr.mgh.harvard.edu> > > >> > > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > >> > > >> > > >> _______________________________________________ > > >> Freesurfer mailing list > > >> Freesurfer@nmr.mgh.harvard.edu <mailto: > Freesurfer@nmr.mgh.harvard.edu> > > >> > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > >> > > >> > > >> > > >> _______________________________________________ > > >> Freesurfer mailing list > > >> Freesurfer@nmr.mgh.harvard.edu > > >> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > > > > > > > _______________________________________________ > > > Freesurfer mailing list > > > Freesurfer@nmr.mgh.harvard.edu > > > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > > > > > > >_______________________________________________ > > Freesurfer mailing list > > Freesurfer@nmr.mgh.harvard.edu > > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > > > >_______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
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