Dear Carles,
> I was wondering why smoothing should be done after realigning and
> normalizing and not before. First, realignment of smoothed images
> should be more robust because high frequency noise is removed. No
> other effect should be produced if all the voxels are convolved
> with the same gaussian kernel. Second, images are normalized to a
> very smooth template. As I understand it is easier (in terms of
> time computing) normalizing smoothed image to a smoothed template
> than doing to non smoothed images; and the result shouldn't be affected.
Yes, your assumption is absolut correct. SPM does this smoothing internally,
so you are indeed coregistering and normalizing smoothed images, but this
transformations are than finally performed on the unsmoothed images.
All thes best,
Karsten
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Dipl. Phys. Karsten Specht
(Medizin Center Bonn, Spessartstrasse 9, 53119 Bonn, Germany)
currently at:
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Department of Biological and Medical Psychology
Section of Cognitive Neuroscience
Aarstadveien 21
5009 Bergen
Norway
http://www.uib.no/ibmp/bjorg/english/
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