fMRI Primer

12.5 Within-Subject Group Analysis

Sometimes you need to do a group analysis within a given subject. For example, I wanted to see whether people’s brains looked different when doing the ES task before getting sad versus afterwards. So I needed to subtract their after-image from their before image. I did each of these individually as explained above.  Now comes the subtraction.
Step 1: Misc Tab Differences
In group level analyses you have the option to cleanup first level standard space images; this wasn’t possible at the individual level. This is a bad thing and you should say no to it.
Cleanup first-level standard-space images

= NO yellow check box. This will screw you up big time if you leave it checked.

Under the DATA tab of FEAT we will start from the bottom.

Saving the .fsfSaving the .fsf file, so you can run it again on a different subject, or re-run it on this subject.  Press save and in the box that pops up, determine what directory you want to save it in (for programs that can be used on multiple subjectsthink of a good name

you will specify that inputs are lower-level FEAT directories – what this means is you are doing a group analysis. In this case, the group is within a given subject. You tell it to expect two analyses – meaning two FEAT directories.  You then select these feat directories, by clicking on the select FEAT directories tab, as shown below.


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