Its because the globals returned by the script are not simply related
to the image intensities. With prop'nal threshold masking, the threshold
defining the region of brain that is included in the analysis is (in your
case) 0.8 times the "global" that is computed for that image.
Why not use absolute threshold masking, or explicit masking?
Best regards,
-John
> I used 2-sample t-test to compare the gray matter concentration between 2
> subject groups.
>
> Global normalization: 'proportional scaling'
> Prop Sca Global mean: 100
> Threshold masking: prop'nal
> analysis thresh: 0.8
> Global calculation: user defined
> globals: spm_load (and choose the ascii file containing the globals derived
> using the get_integrals function in the message dated Oct 25 from John)
>
> However I got the following error message. Any suggestions?
> Plane 121/121, plank 3/3 : ...done
> Warning: No inmask voxels - empty analysis!
>
> > In /usr/local/bin/spm99/spm_spm.m at line 1074
--
Dr John Ashburner.
Functional Imaging Lab., 12 Queen Square, London WC1N 3BG, UK.
tel: +44 (0)20 78337491 or +44 (0)20 78373611 x4381
fax: +44 (0)20 78131420 http://www.fil.ion.ucl.ac.uk/~john
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