Hi,
To reduce global multiple comparison issue, I want to confine my group analysis contrasts in gray mater (GM) only, i.e., excluding voxels in white mater and CSF. To this end, I want to get an average GM mask from all my subjects.
My strategy is to do "Segment" in spm8 for each subject's T1-weighted images. In "Grey Matter," I selected "Native+Modulated+unmodulated." After finishing, I got wcxxx and mwcxxx files, both of which are in standard 2x2x2 space, suggesting they are normalised to standard template. Then I plan to average all subjects' wcxxx (or mwcxxx) files to get an average GM mask from all my subjects.
Can anyone tell me which file should I use? wcxxx files or mwcxxx files?
Or, is my strategy to get an average GM mask from all my subjects appropriate?
Thanks.
Mike
|