Hi,
I 'm not an expart in fMRI study, but I use this strategy.
If your subjects in MNI space, you could use AAL atlas or other atlas to select a GM.
And for changing the voxel size of the mask image, look to this
http://www.nemotos.net/?p=292
Regards,
Arkan
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M.Sc. Arkan Al-Zubaidi
Klinik für Neurologie
UKSH, Campus Lübeck
Paul-Ehrlich-Strasse 1-3, MGZ
23562 Lübeck
0451 317 9313 14
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From: SPM (Statistical Parametric Mapping) [[log in to unmask]] On Behalf Of Mike [[log in to unmask]]
Sent: 12 August 2015 18:11
To: [log in to unmask]
Subject: [SPM] average GM mask
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
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