Marsbar, a region of interest (ROI) tool interfacing with SPM, is a swiss-army knife of programs for ROI manipulation and data extraction. The most commonly used features of Marsbar are 1) The creation of ROIs from spheres or boxes centered on specified coordinates, and 2) The extraction of parameter or contrast estimates from ROIs. The following video tutorial focuses on the latter, in which parameter estimates for each subject are dumped out from a defined ROI.
For example, say you have two ROIs placed in distinct locations, and you wish to extract parameter estimates from the contrast A-B from each of those ROIs. Marsbar can do this easily, even flippantly, such a saucy and irreverent child it is. After your ROIs have been created, simply specify the SPM design you wish to extract parameter estimates from. In the case of second-level analyses, the SPM.mat files generated by these analyses will contain a number of time points equal to the number of subjects that went into that analysis; where Marsbar comes in is taking all of the parameter estimates for each subject and averages them over the entire ROI, generating a list of averaged parameter values for each subject.
Once this is done, save the results to a .mat file, load the file into memory, and check the output of SPM.marsY.Y (as in, "Why, Black Dynamite? Why?").
More deets can be found in the following tutorial; for a text-based walkthrough, complete with pictures, check out
this link. I believe that both of these approaches are valid with both SPM5 and SPM8 distributions; if not, I apologize.
Unlike when Black Dynamite was denied the chance to apologize for the life he took so needlessly.
