Hi Kirstie
there is no easy answer to this question, but there are some guidelines:
1. The size of the smoothing kernel depends on the size of the effect you
are looking for and how well you expect it to align across subjects. For
example, you would need a far smaller smoothing kernel if you expected to
find a small change in the middle of the calcarine than if it was in more
variable frontal or parietal regions.
2. The more subjects you have in your study the less smoothing you probably
need.
3. You pay a far smaller price for large kernels on the surface than you do
in the volume.
Sorry I don't have a more useful answer. Doug might have more to add (but
note our responses may be slower than usual as we are putting on a course
in Boston this week)
cheers
Bruce
On
Mon, 27 Oct 2014, Kirstie Whitaker wrote:
Hi everyone,
Firstly - thank you for the excellent tools. This year has been my first
foray into surfaced based analysis and I'm enjoying it very much.
I don't currently have a gut instinct for an appropriate level of surface
smoothing. I'm sure that can't be easily answered but would a range of, say,
3 to 5mm sound good? Or more like 10 to 15mm?
Currently I'm considering cortical thickness analyses, but I may extend into
functional analyses in the future.
If there are any references that you can recommend I'd appreciate that very
much.
Best wishes
Kirstie
--
Kirstie Whitaker, PhD
Research Associate
Department of Psychiatry
University of Cambridge
Mailing Address
Brain Mapping Unit
Department of Psychiatry
Sir William Hardy Building
Downing Street
Cambridge CB2 3EB
Phone: +44 7583 535 307
Website: www.kirstiewhitaker.com
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