It would probably be easier to use one of the other fsaverage subjects (eg, fsaverage5 which is a 5th order ico). I think we distribute 5 and 6; if not we can get them to you. Also note that you may want to sample to fsaverage (which is 7th order) with mri_vol2surf and then use mri_surf2surf to convert to fsaverageX. These two steps will assure that you average all of the surface data around each sparsely sampled fsaverageX vertex.

doug

On 12/15/10 9:58 PM, Joakim Vinberg wrote:

Hi everybody,

I am interested in doing sub-sampling of functional data for some new analyses. Just about the only reference I can find to sub-sampling of data in FreeSurfer is in mri_surf2surf, which has an optional flag trgicoorder. The comment for this flag is:

"This specifies the size of the icosahedron according to the formula #vertices=10*4^n+2. In general, it is best to use the largest size available."

It would seem that I might be able to use this flag in order to sub-sample surface data by using a smaller n (it seems as if the default for fsaverage is 7 according to the specified formula). Is this correct?

Are there any particular guidelines to n? Other surfaces have a variety of vertices, so it seems that n does not have to be an integer?

If I computer a surface of functional data for a given subject with a specific 'n' and resulting nVertices, should I also calculate an according anatomical surface with the same number of vertices for display and analysis?

Thanks!

Joakim

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