Dear Marsbar users and Mathew,
I recently learned how to extract mean voxel value (summary time courses) using extract ROI full options on a spm cluster and by exporting it to the matlab workspace.
I have few basic questions. The VBM design I used was in SPM5 using full factorial having 2 groups and 3 covariates. I also used ancova for global normalization. Extract ROI has 2 options 1) obtain raw data 2) From SPM design.
I obtained the raw data first which I assume has not been adjusted for the covariates. When I tried comparing the volumes for the 2 groups using ancova and adjusting for the covariates using SPSS there were no significant differences? Any comments or suggestions? Maybe I am doing something wrong in SPSS.
If I use the SPM design to get the GM values will it control/adjust for the various design parameters applied including the covariates? Or will it just adjust for global normalization but not for covariates? If I use this option do I have to look for the 'y' or do I still export the summary time course in my matlab workspace to look at the volumes?
Lastly, are the volumes reported in mL?
Kindly advise,
Manish Dalwani
Sr. PRA
University of Colorado
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