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For clarification....

Isotropic smoothness is the state of equal x-, y- and z-FWHM smoothness.  Non-isotropic smoothness is never a problem (SPM has never assumed isotropic smoothness).

Non-stationary smoothness is spatially varying FWHM smoothness.  SPM's cluster size inference assumes stationary smoothness; dealing with nonstationarity requires the NS toolbox (directly or via the VBM toolbox).

-Tom

On Thu, Jun 19, 2008 at 1:57 PM, Simone Reinders <[log in to unmask]> wrote:
Hi Austin,

Isn't the non-isotropic smoothness related to the smoothness of the
statistical inference situation, i.e. the resels?

http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0802&L=SPM&P=R39928&D=0&I=-3&m=24842

Regards,
Simone.

On Mon, Jun 9, 2008 at 10:04 PM, Austin Woolard
<[log in to unmask]> wrote:
> Is it necessary to correct for non-isotropic smoothness when one has
> isotropic voxel sizes during the first-level analysis in SPM5?
>
> Any relevant information would be very helpful.  Thanks!
>



--
Dr. A.A.T. Simone Reinders, MSc PhD
King's College London
Institute of Psychiatry (IoP)
Box P063, De Crespigny Park
London SE5 8AF
United Kingdom




--
____________________________________________
Thomas Nichols, PhD
Director, Modelling & Genetics
GlaxoSmithKline Clinical Imaging Centre

Senior Research Fellow
Oxford University FMRIB Centre