Category:ROI

The brain volume is a relatively large space when expressed in terms of the voxels (3D space) or vertices (surface space) that describe it. Regions of Interest (ROI) are one way to restrict analyses to subregions within the brain. This might be done for the purposes of analytic tractability (e.g., interregional connectivity, which scales geometrically with the number of regions analyzed), to maximize statistical power by excluding uninformative voxels that would nonetheless factor into your statistical thresholds, or for theoretical reasons to limit the scope of discussion for a manuscript (there's no need to explain curious activations in regions that were never analyzed!)