Dear Kevin:
One caveat which you may know if you've followed the list, is that the
con**.img and beta*.img images have the areas outside the brain values set
to NaN. Thus any smoothing operation at this stage will lose the outer layer
of voxels. Methods of dealing with that have been discussed previously by
John and Russell Poldrack I believe.
Darren.
Karl Friston wrote:
> Dear Kevin,
>
> > Karl Friston wrote:
> >
> > > ...Increasing
> > > the smoothing (of the con??? or beta???.img) prior to the 2nd level
> > > analysis might improve your sensitivity (e.g. 8mm FWHM).
> >
> > Let me make sure I understand this.
> >
> > Do you mean that you would smooth the statistical summary image before
> > running the across-subjects analysis, after the con???.img itself had
> > already been generated by smoothing the original data?
>
> Yes. This avoids having to re-run the first-level analysis. You would
> only need to smooth a little bit at the second level to supplement the
> first-level smoothing.
>
> I hope this helps - Karl
--
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Darren R. Gitelman, M.D. E-mail: [log in to unmask]
Cognitive Neurology and Voice: (312) 908-9023
the Alzheimer¹s Disease Center Fax: (312) 908-8789
http://www.brain.nwu.edu
Northwestern Univ., 320 E. Superior St., Searle 11-470, Chicago, IL 60611
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