The term area 9 refers to an area defined by internal structure and located rostrally in the superior frontal gyrus. Bounded laterally by the superior frontal sulcus, it extends onto the medial surface of the hemisphere where it is bounded by the cingulate sulcus. Identified on the basis of multiple stains, it is bounded rostrally by area 10, caudally by area 8, laterally by area 9/46, and on the medial surface, ventrally, by area 32ac ( Petrides-2012 ). Architectonically it is part of the dorsolateral prefrontal cortex, which is one of the most variably segmented parts of human cerebral cortex ( Zilles-1990 ). In this segmentation it is one of four parts. The others are area 8, area 9/46, and area 46. Its equivalent in the macaque is similarly located, except that it is partially bounded laterally by area 46. Also, in the macaque it is subdivided into area 9M and area 9L ( Petrides-2009 ). As granular prefrontal cortex, it has no equivalent in the rat ( Zilles-2012 ).