Beauchamp:ROIanalysis

If you would like to compare activity across subjects in threshold-defined areas, an ROI analysis may be right for you!

For example, we may be interested in comparing amplitude of activity in auditory cortex during different types of speech stimuli in people with different behavioral characteristics. While we could use a group whole-brain analysis to see if there are any voxels in a combined map within auditory cortex that show a differential response, it may be better to separately define each auditory ROI in each subject using strict and reproducible criteria, such as T stat > 3.

To facilitate this process, the surfaces in SUMA come already parcellated into useful regions. With the parcellation, each anatomical region is assigned a value (same in left and right hemisphere). So, for each subject, we can find active areas within these anatomical locations to use as ROIs. Depending on when the surface was made, the parcellation is done either with a 2005s or 2009s atlas. Here are the parcellation values corresponding to 5 regions of interest:

2005s:

 Auditory cortex                        33, 81
 Extrastriate visual cortex (V5/MT)     60
 Fusiform gyrus                         17, 63
 Inferior frontal gyrus                 6, 72
 Superior temporal sulcus               80