dear SPM gurus,
why do mask.img files after a 1st level fixed effect analysis of
several spatially normalized fMRI studies sets turn out to be
NON-identical, even after inclusion of an explicit mask file in the
variable :
jobs{1}.stats{1}.fmri_spec.mask{1} = 'myMask.img' ;
moreover, during the 2nd level RFX analysis, i experience a similar
problem: specifying a mask file in variable complex :
jobs{1}.stats{1}.factorial_design.masking.tm.tm_none = [] ;
jobs{1}.stats{1}.factorial_design.masking.im = 0 ;
jobs{1}.stats{1}.factorial_design.masking.em{1} = 'myMask.img' ;
doesn't have much an effect on the outcome of the resulting 2nd level
mask.img file. while computing with hundreds of 1st level contrasts,
somewhere down the line one or more strong outliers spoil and ruin the
entire analysis.
i need to add on here that undesired voxels are, as epxected, excluded
with the supplied mask at the 1st level, but additional voxels within
the brain disappear as well although the explicit mask specifically
marks them with a value of '1'.
what am i missing here? thanks for any input, bye,
pisti
-----
www.pistikem.org
[log in to unmask]
|