The term area 23 (macaque) refers to a portion of the posterior cingulate gyrus defined on the basis of cytoarchitecture and connectivity in the macaque ( Vogt-1987 ). It has three subdivisions: area 23a (macaque), area 23b (macaque) and area 23c (macaque). An equivalent area exists in the human ( Vogt-1995 ). For a more recent segmentation of this area by the same authors later in their studies ( Vogt-2012 ) see area 23.