BTW: You can't "sum" the thicknesses across the various regions in the
aparc files, as that would be a meaningless measure. You either need to
compute the average cortical thickness as I suggested, or compute a
weighted mean from the data in the aparc files, in which you weight each
region's thickness by its proportion of the total surface area.
cheers,
-MH
On Thu, 2010-12-16 at 11:57 -0600, Michael Harms wrote:
> Yes, I think that using average cortical thickness is a reasonable
> covariate to use in thickness analyses. And total cortical surface area
> likewise if you are analyzing regional surface areas, although in the
> case of surface area you need to decide whether to use areas based on
> the GM or WM surface, or some "mid"-surface in-between.
>
> Use mris_anatomical_stats along with the {lh,rh}.cortex.label files to
> compute these statistics for the overall cortex. If the optional
> <surface name> at the end of the command is 'pial', then the area will
> be based on the pial surface. If nothing is specified, it'll be based
> on the white (default) surface. If you want the area based on the mid-
> surface, you either need to construct that surface first (if it isn't
> already computed by recon-all in the most recent FS versions) or run the
> command separately for the 'pial' and 'white' surfaces and then average
> the resulting areas].
>
> cheers,
> -MH
>
> On Fri, 2010-12-17 at 01:42 +0800, Liukarl wrote:
> > Hello, Freesurfer experts:
> >
> >
> >
> > I found to report subcortical volumetric measure, ie, the volume of
> > amygdale, people tend to use icv as a control variable. Is there any
> > corresponding measure to correct the cortical thickness/area/volume
> > results from autorecon3. Because we have priori hypothesis of
> > hemisphere dichotomy of cortical structures, we need some control
> > variable for each hemisphere. We want to use an overall measure for
> > each hemisphere as a control variable. For example, to measure the
> > group differences on rh_paracentral_thickness, we will use the
> > rh_whole_thickness as a contral variable (which is the sum of the
> > thickness measures of all the ROIs in the right hemisphere produced by
> > Freesurfer). Similarly, to measure the group differences on
> > rh_paracentral_area and rh_paracentral_volume, we will use the
> > rh_whole_area and rh_whole_area as a contral variable respectively. Is
> > this a valid approach to report our results?
> >
> >
> >
> > Thanks a lot!
> >
> >
> >
> > Karl
> >
> >
> >
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