To resample from ico4, use --srcsubject ico --srcicoorder 4
If you use nnf, some of the source vertices may not get sampled. If you use
nnfr, you should get clusters of vertices for every ico4 vertex. You should be
able to find the clusters and then pick the vertex with max intensity for each
cluster. That set of max intensity vertices defines the mapping between ico 4
and the single subject.
If you do this, you can use the mgh format and then display directly on an ico4
surface. Doug mentioned that you could somehow create a downsampled average
subject.
If you get this working, please let me know.
> Date: Tue, 29 Jan 2008 00:25:08 +0000
> From: [EMAIL PROTECTED]
> To: [EMAIL PROTECTED]
> Subject: Re: [Freesurfer] Creating average overlays for time-varying data
> (MEG)
> CC: freesurfer@nmr.mgh.harvard.edu
>
> A question related to this: is it possible to take a surface overlay (.w
> format) containing a set number of vertices, all with the same value, in
> one subject space and warp it to another subject while keeping the same
> number of vertices? I would like to try to define a set of source points
> on an average surface, and then warp those points back to each
> individual subject for source analysis. Perhaps the 'ico' option of
> mri_surf2surf solves this problem, but I am not fully clear on how that
> works. Any pointers to documentation on this would be most appreciated.
>
> I have tried using mri_surf2surf to achieve this, but I either end up
> with too little (nnf) or too many vertices (nnfr) on the target surface.
> I have had some problems with resampling a sparse set of individual data
> points to an average surface and smoothing (on source or target
> surfaces), as the smoothing seems to introduce entirely new foci of
> activity, particularly around the insula. Therefore, I am trying to find
> a way to have a set of common source points so that smoothing can be
> avoided until the final step to display the data.
>
> Thanks in advance,
>
> P.
>
> Don Hagler wrote:
> > If you wanted to go from a sparsely valued single subject surface (i.e.
> > decimated dipoles) to ico4, it seems that you would probably miss many
> > of your dipole vertices because they wouldn't necessarily be the ones
> > closest to the ico4 vertices. Going from decimated dipoles to ico7 may
> > work ok, although you may still miss a few dipoles, which is why
> > smoothing before sampling to ico seems to be a good idea. And we have
> > to smooth anyway before doing group analysis because the ico7 vertices
> > that correspond to a single subject's decimated dipoles will vary from
> > subject to subject.
>
> --
> Pádraig Kitterick
> Graduate Student
> Department of Psychology
> University of York
> Heslington
> York YO10 5DD
> UK
>
> Tel: +44 (0) 1904 43 3170
> Email: [EMAIL PROTECTED]
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