On Feb 5, 2008 3:17 PM, Bruce Fischl <fischl@nmr.mgh.harvard.edu> wrote:

Hi George,

there are two different questions here: (1) what anatomical boundary does
each surface represent, and (2) how do you sample functional data onto
the surface. For (1) the pial surface is indeed the boundary between gray
matter and CSF, but for (2) once you choose a sampling strategy (anywhere
from gray/white out to pial) the fMRI data can be displayed on any of the
surfaces simply as a visualization. Is that clear?

Bruce

On Tue, 5 Feb 2008, George He wrote:

> Hi freesurfer experts,
> It seems to me the pial surface should be the surface of gray matter, but
> when I overlay functional activations on it, it seems to be surface of white
> matter.
> The reason I think so is that when I load the same activation in both
> tksurfer and tkmedit,
> if I click on an activated area (or any point) on the pial surface in
> tksurfer, save it, and load it in tkmedit, the point will land on the
> yellow/green lines while the tksurfer and tkmedit show the same talairach
> coordinate for the point.
> If I click on a point that is on the red line in tkmedit, save it, and load
> it in tksurfer, they (tkmedit and tksurfer) show different talairach
> coordinates for the points.
> Question: what is the truth and what should I expect?
> Thanks,
> George
>