The term area 13a refers to one of four subdivisions of area 13 in the orbital gyri of the human cerebral cortex. Defined on the basis of multiple stains, it is a small area of agranular cortex located just rostral to the junction of the olfactory tract with the cerebral cortex. It is bounded medially by another small agranular area 14c, laterally by area 13m, and rostrally by area 13b. The other subdivision is area 13l. For the relations of this segmentation and terminology to others, see Ongur-2003. Its equivalent in the macaque is area 13a (macaque). Unlike most prefrontal cortex, which is uniquely primate and granular, it may have an equivalent in the agranular cortex of the rat ( Wallis-2012 ). See orbital areas (rodent).