On 01/19/2013 03:18 PM, Alex Kell wrote:
> Hi Freesurfers,
>
> I have two unrelated questions.
>
> 1. I want to pre-whiten some functional data without running a GLM on
> them (we're going to run the GLM in matlab). It looks like fsfast
> does autocorrelation correction as a part of the selxavg3-sess
> wrapper. I tried poking around on the wiki and mailing archives, but
> I can't find how to pre-whiten the data without running a GLM. Is
> there a straightforward way? If not, I guess we could just do it in
> matlab.
FSFAST uses an AR1 model. It computes the AR1 from the residuals (thus
needing to run the GLM first). The voxel-wise AR1 is spatially smoothed,
then binned into 10 bins. All the voxels in each bin are then analyzed
in the same way.
>
> 2. Separately, we're bringing some volume masks to the surface and are
> preprocessing them with dilation and erosion to clean them up. We're
> trying to get a sense of how much is a reasonable amount to dilate and
> erode by, and it would be helpful to know about how far apart the
> adjacent surface vertices are. Roughly, what's the mean distance
> between adjacent vertices?
About 1mm
doug
>
> Thanks in advance.
>
>
> Best,
> Alex
>
>
>
>
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--
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
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