Hi,
I'm attempting to conduct a conjunction analysis with VBM data within SPM, but I could use a little help. I'm using a regression model to look for volumetric changes associated with a test score. I also have a second variable representing a measured exposure to a chemical. It has already been established in the literature that increased exposure to this chemical results in a higher test score, which matches my data. I have conducted VBM analyses that suggest increased test scores are associated with a regional volumetric decrease in the brain, and that increased exposure to this chemical results in a similar regional volumetric decrease, so I am interested in analyzing the area of overlap between the two analyses.
I guess I'm not positive how to do this using a regression model. I've read that in SPM, I'm supposed to select the contrasts that I'm interested in comparing in the "Results" menu; however, my analyses have been separate so the contrasts for each variable are separate. Should I run a regression with both variables in the same model, create contrasts for both [0 -1 0] and [0 0 -1], and use that to run the conjunction analysis? Or does someone know of another way? Any help would be greatly appreciated.
Thanks,
Travis
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