Hello SPM experts,
I have a rather basic question about factorial design at the second level. I have a 2(Regulate vs. Permit) by 2(High reward vs low reward) design that I am testing. At the first level i defind t contrasts for all possible combinations, in cluding the contrast for each condition on its own. I've done ROI analysis using these contrasts and at the second level I've been having masking issues with voxels of my ROI by the second level mask. To circumvent this I ran all my ROI analyses across my specified t contrasts at the first level and extracted my parameter estimates and am running random effects analyses outside of SPM. One such analysis has been this 2X2 ANOVA whereby, for each of my ROIs I have entered I've made dependent variable the parameter estimates for each level/condition of that ROI. For example, when testing the full factorial ANOVA on Right nucleus accumbens, for my conditions and levels, I did the following
In SPM generate a contrast for Regulate High, Regulate Low, Permit High, Permit Low). Run my ROI analysis in marsbar using each of these contrasts and extract parameter estimates. In SPSS, set up a column defining Strategy(1 for Regulate, 2 for Permit) and a column defining reward(1 for low, 2 for high) and a column with my parameter estimates across all four conditions added in with accordance to the first two columns. My anova is then run using the Strategy and reward column as my fixed factors, and the column of parameter estimates as my dependent measure
My concern is that I have done it this way rather than defining the f contrasts at the first level. I've managed to confuse myself as to whether or not I've violated a variance assumption here. I would appreciate any insight, thank you! I've detailed a little more of how I set up the factorial design below
In SPM generate a contrast for Regulate High, Regulate Low, Permit High, Permit Low). Run my ROI analysis in marsbar using each of these contrasts and extract parameter estimates. In SPSS, set up a column defining Strategy(1 for Regulate, 2 for Permit) and a column defining reward(1 for low, 2 for high) and a column with my parameter estimates across all four conditions added in with accordance to the first two columns. My anova is then run using the Strategy and reward column as my fixed factors, and the column of parameter estimates as my dependent measure
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