[caret-users] importing thresholded functional data
donna at brainvis.wustl.edu
Thu Feb 25 09:16:13 CST 2010
If it makes you feel better, you could apply the inverse transform to
your surface coordinates (see Window: Transformation Matrix Editor or
caret_command -surface-apply-transformation-matrix), so that you can map
your Z-map directly to the "native" surface.
I hope others speak up if they disagree with me, but reporting
interpolated z-values should be pretty far down on your stack of things
to worry about.
It would be different if this were a label/ROI file you were mapping,
but then you would use nearest neighbor (NN). Of course, that is
another alternative -- using NN for your Z-map. But I'm guessing these
are bigger fMRI sized voxels, so there are concerns there.
I think you'll sleep better if you bring your surface to your volume.
On 02/25/2010 03:16 AM, wolf zinke wrote:
> I am sorry for this naive an likely many time answered question, but a
> first search did not bring up any clear statement to this issue.
> I use caret to view functional data on inflated monkey brains. The data
> was analysed with FSL on data oriented according to a coordinate system
> based on eye and ear bars, but the caret files use the
> anterior,posterior commisure, hence I apply a transformation to my
> thresholded functional data (z-values) including a trilinear
> interpolation. This of course lead to subthreshold values surrounding
> the patches, and reduced, more smooth values within patches. In the step
> of mapping the volume data to the surface I again apply
> interpolation/averaging of the z-values.
> I am wondering now, if this is an accepted procedure and that the
> interpolation of statistical maps is in general not seen as a serious
> problem. Though the statistics of the maps are reduced and smeared, I
> doubt that this introduces a serious misplacement of the activation
> foci. However, I don't fell well to present the range of z-values as
> 'z-values' anymore, because of the interpolation.
> I am happy for any pointers regarding such issues.
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