This chapter presents the advantages of the use of functional regions of interest along with its specific concerns, and provides a reference to Karl J. Friston related to the subject. Functionally defined ROI help to test hypotheses about the cognitive functions of particular regions of the brain. fROI are useful for specifying brain locations and investigating separable components of the mind. The chapter provides an overview of the common and uncommon misconceptions about fROI related to assumptions of homogeneity, factorial designs (...) versus independent localizers, a summary measure, and the naming of fROI. (shrink)