JISCMail - SPM Archives

Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Postdoctoral Research Fellow, GRECC, Bedford VA
Website: http://www.martinos.org/~mclaren
Office: (773) 406-2464
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On Tue, May 26, 2015 at 11:11 PM, Tamara Sussman <[log in to unmask]> wrote:

Donald,
Thanks so much for your quick reply!

(and sorry for my late response - I thought this message was posted a few days ago, but it seems to not have made it out to the list)

I tried adding the number of volumes and the degrees of freedom, and the number of the estimate DID decrease by about 1000, but that is still leaving my estimates at around 5000 - still way too high.

Any thoughts about why this may be happening?

Also, I used this code, which produced reasonable number. I found it on the list (thanks to Jim Lee):

"The smoothness estimates in SPM.xVol.FWHM are in units of VOXELS, so
you need to multiply by the voxel dimensions to get them in mm.
Something like this:

load SPM.mat;
M = SPM.xVol.M;
VOX = sqrt(diag(M(1:3,1:3)'*M(1:3,1:3)))';
FWHM = SPM.xVol.FWHM;
FWHMmm= FWHM.*VOX;
disp(FWHMmm);"

Is this a good alternative way to estimate smoothness?
Thanks so much!
Tamara