Hello!
I am conducting a meta analysis, and some studies report 2 contrasts that are of interest to the meta analysis. I know that I can combine those contrasts into one map using the combine images function, but I am curious about the math that goes into this. How are the maps combined? Are the effect sizes and coordinates averaged or taken into account in some way so that if the two contrasts have some similar coordinates, they are not over represented in the combined image? Or are the coordinates simply pooled together without taking into consideration over representation? I have looked at all the papers posted on the SDM website, but I have't found any information on how the combining images function works. Could someone please explain how the function works?
Thank you!
Susie