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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