[caret-users] Talairach group data to individual surface

[Donna Dierker]

Hi Sarah,

This is not something we do every day -- map group results to an 
individual's surface.  Maybe some context might clarify.

But let me illustrate an example where something like this might make 
sense.  Suppose I have functional group differences, and I want to 
investigate whether anatomical difference might underly the functional 
differences.  I can imagine doing something like this:

* Use some sort of volume-based registration (VBR) to warp the 
individual's anatomical volume into the same stereotaxic space as my 
functional group results.  Spend a fair amount of time fussing about 
what VBR method to use (e.g., linear vs nonlinear).  It might be 
reasonable to use the same VBR method used to generate the functional 
group results, but give this step some thought before charging ahead.

* Use caret_command or AFNI's Vecwarp to apply the resulting affine 
transform, if a linear VBR method was used, to your individual's 
surface, so the surface is now in atlas space.  (If a nonlinear method 
is used, then you'll need to apply the deformation map using alternate 
methods.  The SPM links here give you a feel for how that works:

    http://brainvis.wustl.edu/help/pals_volume_normalization

* Map the functional results onto the atlas-space surface.

* Perhaps smooth/threshold the results, using Caret's Attributes: 
Metric: Clustering and Smoothing and/or Surface: ROI features.

* Perhaps even use Surface: ROI to threshold the map and convert it to 
Paint, so that now I have a ROI on the individual's surface; then, 
Attributes: Paint: convert paint column to paint volume to project the 
ROI on the individual's surface to the atlas-warped individual's 
anatomy.  I might use this as a starter segmentation, perhaps clean it 
up, perhaps not, for the purpose of applying some sort of volumetric 
morphometric method.

This may be nothing like what you want to do, but it's the kind of 
context under which it might make sense to map group fMRI onto 
individual surfaces.

Donna

On 12/06/2007 09:11 AM, Sarah Hillenbrand wrote:
> I have functional group data in Talairach space that I need mapped to an
> individual surface.  I'm having trouble with this and am not sure at which
> step in the process I may have gone astray.
>
> What are the correct steps to follow here?
>
> Much obliged,
> Sarah
>
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